JP2015083661A - Porous film and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous film mainly containing a biodegradable resin, good in balance of contractility resistance with time and fracture point elongation, and excellent in moisture permeability.SOLUTION: There is provided a porous film containing a biodegradable resin (A), a filler (B) of 1 to 70 mass% in 100 mass% of all components of the porous film, having porosity of 5 to 80%, and elongating in only one direction. Hereafter a direction of elongation is referred to as an elongation direction and a direction orthogonal to the elongation direction is referred to as an orthogonal direction. The porous film has thermal shrinkage percentage in the elongation direction of 0 to 10%, thermal shrinkage percentage in the orthogonal direction of -5 to 5%, and fracture point elongation in the orthogonal direction of 15% or more.

Description

  The present invention relates to a porous film that is mainly composed of a biodegradable resin, has a good balance between shrinkage resistance with time and elongation at break, and is excellent in moisture permeability.

  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. For example, polylactic acid has attracted attention as a resin that satisfies both requirements and is relatively advantageous in terms of cost. However, when trying to apply polylactic acid to flexible film applications in which polyolefins such as polyethylene are used as typical materials, they lack flexibility and impact resistance, so various attempts have been made to improve these properties and put them to practical use. Has been made.

  In the field of porous films, for example, Patent Document 1 discloses a porous film obtained by stretching a sheet containing a polylactic acid resin, a thermoplastic resin other than a polylactic acid resin, and a filler. Patent Document 2 discloses a porous sheet obtained by stretching at least uniaxially a sheet containing a polylactic acid resin, a filler, and a general polyester plasticizer. Further, Patent Document 3 discloses a biodegradable porous film obtained by melting a resin composition containing an aliphatic polyester, a thermoplastic resin, a filler, and a plasticizer, forming the film or sheet, and then stretching the resin composition. It is disclosed.

WO2012 / 023465 pamphlet JP 2007-112867 A JP-A-9-291165

  In the techniques described in Patent Documents 1 and 2 above, porous films satisfying a certain moisture permeability were obtained, but their performance was not sufficient, and they were resistant to shrinkage with time and elongation at break. The surface was inferior. In particular, regarding a porous film made by stretching in only one direction, both the shrinkage resistance with time in the stretching direction and the elongation at break in the direction perpendicular to the stretching direction were insufficient. The shrinkage resistance with time and the elongation at break are performances essential for processing or using a porous film.

  In other words, so far, porous films having excellent moisture permeability, biodegradability, and high biomass have been studied, but their moisture permeability is not sufficient, and they are resistant to shrinkage with time and elongation at break. The invention of a porous film stretched only in one direction and having excellent performance has not yet been achieved.

  In view of the background of such conventional technology, the present invention is intended to provide a porous film stretched only in one direction and excellent in moisture permeability, shrinkage resistance with time and elongation at break.

  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.

Aspects of the present invention are as follows.
1) Including biodegradable resin (A)
In 100% by mass of all components of the porous film, 1 to 70% by mass of the filler (B) is contained,
The porosity is 5 to 80%,
It is stretched in only one direction (hereinafter, the stretched direction is referred to as the stretching direction, and the direction orthogonal to the stretching direction is referred to as the orthogonal direction)
The heat shrinkage rate in the stretching direction is 0 to 10%,
The heat shrinkage in the orthogonal direction is -5 to 5%,
A porous film having an elongation at break in an orthogonal direction of 15% or more.
2) Including biodegradable resin (A),
In 100% by mass of all components of the porous film, 1 to 70% by mass of the filler (B) is contained,
The porosity is 5 to 80%,
The heat shrinkage rate in the direction in which the heat shrinkage rate is maximized (hereinafter, the direction in which the heat shrinkage rate is maximized is referred to as direction A, and the direction orthogonal to direction A is referred to as direction B) is 0 to 10%.
The thermal shrinkage in the direction B is -5 to 5%,
A porous film having an elongation at break in the direction B of 15% or more.
3) The porous film according to 1) or 2), wherein the tear propagation resistance in the stretching direction or direction A is 1,000 mN / mm or less, and the tensile strength in the orthogonal direction or direction B is 15 MPa or less. .
4) The porous film according to any one of 1) to 3), wherein the moisture permeability is 500 g / (m ² · day) or more.
5) The porous film according to any one of 1) to 4), wherein the biodegradable resin (A) is a polylactic acid resin.
6) The porous film as described in 5), which contains a thermoplastic resin other than a polylactic acid resin.
7) The thermoplastic resin other than the polylactic acid resin is selected from the group consisting of 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. The porous film according to 6), comprising a combination of at least one resin selected from the group consisting of an aliphatic polyester resin and an aliphatic aromatic polyester resin.
8) A process of discharging and casting the molten resin (hereinafter referred to as a casting process), a process of stretching the film in one direction (hereinafter referred to as a stretching process), and a process of heating the film (hereinafter referred to as a heat treatment process) in this order. A method for producing a porous film comprising:
The method for producing a porous film according to any one of 1) to 7), wherein the temperature in the heat treatment step is 30 to 75 ° C.
9) The method for producing a porous film according to 8), wherein in the stretching step, the film is stretched 1.5 to 4.5 times.
10) In the casting step, casting is performed so that an angle formed between a film made of molten resin discharged from the lip of the die and a vertical plane passing through the lip of the die is 15 to 70 °. , 8) or 9).

  According to the present invention, a porous film excellent in moisture permeability, shrinkage resistance with time, and elongation at break is provided. The porous film of the present invention can be preferably used for applications that mainly require moisture permeability, shrinkage resistance with time and elongation at break. Specifically, agricultural materials such as multi-films, forestry materials such as fumigation sheets, bed sheets, pillow covers, sanitary materials such as sanitary napkins and paper diapers, clothes for rain, clothing materials such as gloves, garbage bags It can be preferably used for various packaging materials, such as bags for food and compost bags, food bags such as vegetables and fruits, and industrial products.

The schematic cross section of an example of the nozzle | cap | die and cooling drum vicinity in a casting process.

  The present invention has succeeded in solving the above-mentioned problems for the first time as a result of intensive studies on the above-mentioned problems, that is, a porous film excellent in moisture permeability, shrinkage resistance with time and elongation at break. That is, the first aspect of the present invention (hereinafter referred to as the porous film 1 of the present invention) includes the biodegradable resin (A), and 1% of the filler (B) is contained in 100% by mass of all components of the porous film. -70% by mass, the porosity is 5-80%, and is stretched in only one direction (hereinafter, the stretched direction is referred to as the stretch direction, and the direction orthogonal to the stretch direction is referred to as the orthogonal direction), A porous film having a heat shrinkage rate in the stretching direction of 0 to 10%, a heat shrinkage rate in the orthogonal direction of -5 to 5%, and an elongation at break in the orthogonal direction of 15% or more. .

  The second aspect of the present invention (hereinafter referred to as the porous film 2 of the present invention) includes the biodegradable resin (A), and the filler (B) is contained in 100% by mass of all components of the porous film. The direction including 1 to 70% by mass, the porosity is 5 to 80%, and the thermal contraction rate is maximum (hereinafter, the direction in which the thermal contraction rate is maximum is referred to as direction A, and the direction orthogonal to direction A is The heat shrinkage rate in the direction B) is 0 to 10%, the heat shrinkage rate in the direction B is −5 to 5%, and the elongation at break in the direction B is 15% or more, A porous film.

  Hereinafter, the porous film 1 of the present invention and the porous film 2 of the present invention are collectively referred to as the present invention or the porous film of the present invention.

  Hereinafter, the porous film of the present invention will be described.

(Biodegradable resin (A))
It is important that the porous film of the present invention contains a biodegradable resin (A). The biodegradable resin (A) is not particularly limited as long as it is a biodegradable resin.

  In the present invention, “having biodegradability” means that the biodegradable resin (A) in the film is JIS K6955 (2000), JIS K6951 (2000), JIS K6953-1 (2011), or JIS K6953. -2 (2010), JIS K6955 (2006) means that the biodegradability is 60% or more within one year.

As the biodegradable resin (A) in the porous film of the present invention, aliphatic polyester resins, aliphatic aromatic polyester resins, polysaccharides, polyvinyl alcohol resins and the like can be used.

  As the aliphatic polyester resin, for example, polylactic acid resin, polyglycolic acid resin, polyhydroxybutyrate resin, polycaprolactone resin, polybutylene succinate resin, or a copolymer thereof can be used. Details of the polylactic acid resin will be described later. These may be isomers or may be copolymerized with other components. For example, specific examples of the polyhydroxybutyrate resin include poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-3hydroxyhexanoate), poly (3-hydroxybutyrate-3hydroxy Variate) and the like. Specific examples of the polybutylene succinate resin include polybutylene succinate, poly (butylene succinate adipate), and poly (butylene succinate lactide).

  Specific examples of the aliphatic aromatic polyester-based resin include poly (ethylene succinate / terephthalate), poly (butylene succinate / terephthalate), poly (butylene adipate / terephthalate), and copolymers thereof.

  Specific examples of the polysaccharide include starch and derivatives thereof, cellulose and derivatives thereof, hemicellulose and derivatives thereof such as glucomannan, chitin / chitosan and derivatives thereof, and the like. In addition, as a resin containing starch, a biodegradable resin “Mater-bi (registered trademark)” of Novamont Co., Ltd. can be used.

  As the biodegradable resin (A), the above may be used alone or two or more of the above may be blended. Alternatively, two or more types of the above copolymers may be used.

  Among these, the biodegradable resin (A) preferably includes a polylactic acid-based resin from the viewpoints of biomass properties, cost, processability, and the like. Below, polylactic acid-type resin is demonstrated concretely.

(Polylactic acid resin)
The polylactic acid-based resin is a polymer mainly composed of an L-lactic acid unit and / or a D-lactic acid unit. 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.

  As the polylactic acid resin, poly L-lactic acid, poly D-lactic acid and the like are preferably used. 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 porous film of 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 the mechanical strength of the porous film. From the standpoint of maintenance, 80 to 100 mol% is preferable in 100 mol% of all lactic acid units, and more preferably 85 to 100 mol%.

  The crystalline polylactic acid resin referred to in the porous film of the present invention means that the polylactic acid resin is allowed to stand for 1 hour under heating at 100 ° C., and then from 0 ° C. to 300 ° C. at a temperature rising rate of 20 ° C./min. When measured with a differential scanning calorimeter (DSC), it means 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 resin referred to in the porous film of the present invention refers to a polylactic acid resin that does not exhibit a clear melting point when measured in the same manner.

  As will be described later, the polylactic acid resin used as the biodegradable resin (A) is preferably a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin.

  The polylactic acid resin used in the porous film of the present invention may copolymerize other monomer units other than lactic acid. Other monomers include glycol compounds such as ethylene glycol, propylene glycol, butanediol and polyethylene glycol, dicarboxylic acids such as oxalic acid, adipic acid and terephthalic acid, hydroxycarboxylic acids such as glycolic acid and hydroxybutyric acid, caprolactone, etc. Of lactones. 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.

  In addition, regarding the polylactic acid resin used in the porous film of the present invention, when the main component is poly L-lactic acid, poly D-lactic acid is used. When the main component is poly D-lactic acid, poly L-lactic acid is used. It is also preferable to mix a small amount. 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. In addition, a main component here means the component exceeding 50 mass%, when the sum total of the polylactic acid-type resin in a film is 100 mass%.

  Furthermore, the polylactic acid resin used in the present invention is preferably a polylactic acid block copolymer composed of a segment composed of an L-lactic acid unit and a segment composed of a D-lactic acid unit from the viewpoint of improving heat resistance. . In this case, since the polylactic acid block copolymer forms a stereocomplex crystal in the molecule, the melting point is higher than that of a normal crystal. In order to efficiently form a stereocomplex crystal, the mass average molecular weight of the polylactic acid block copolymer is X, among the mass average molecular weight of the segment composed of L-lactic acid units and the mass average molecular weight of the segment composed of D-lactic acid units. When the larger side is Y, it is preferable that the segment length satisfy Y <X / 2.

The mass average molecular weight of the polylactic acid resin used in the porous film of the present invention is preferably 50,000 to 400,000, and preferably 70,000 to 300,000 in order to satisfy practical mechanical properties, water resistance and decomposability. More preferably, it is 100,000 to 250,000. In addition, the mass average molecular weight here refers to a molecular weight calculated by a polystyrene conversion method after measurement with a chloroform solvent by gel permeation chromatography (GPC).

  As a method for producing a polylactic acid-based resin, 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.

(Mixing of crystalline polylactic acid resin and amorphous polylactic acid resin)
The polylactic acid resin used as the biodegradable resin (A) in 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.

  That is, by containing a crystalline polylactic acid resin as the polylactic acid resin that is the biodegradable resin (A), the heat resistance and blocking resistance of the film are improved. In addition, when using a block copolymer plasticizer, which will be described later, the crystalline polylactic acid-based resin forms a co-crystal with the polylactic acid segment of the block copolymer plasticizer, thereby greatly improving the bleed-out resistance. To do.

  On the other hand, by containing an amorphous polylactic acid-based resin as the polylactic acid-based resin that is the biodegradable resin (A), it 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 is a content ratio of L-lactic acid units in poly L-lactic acid, or D in poly D-lactic acid. -The content rate of a lactic acid unit is 96-100 mol% in 100 mol% of all lactic acid units, More preferably, it is 98-100 mol%.

  When the total of the polylactic acid-based resin in the porous film of the present invention is 100% by mass (when the total of the crystalline polylactic acid-based resin and the amorphous polylactic acid-based resin is 100% by mass), the crystalline polylactic acid The mass ratio of the resin is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, and still more preferably 20 to 40% by mass.

(Thermoplastic resin other than polylactic acid resin)
The porous film of the present invention preferably contains a thermoplastic resin other than a polylactic acid resin from the viewpoint of improving moisture permeability, shrinkage resistance with time, and elongation at break. Although it does not specifically limit as thermoplastic resins other than this polylactic acid-type resin, Biodegradable resin (A) other than a polylactic acid-type resin can be used. Furthermore, thermoplastic resins other than polylactic acid resins include polyacetal resins, polyolefin resins such as polyethylene and polypropylene, polyamide resins, acrylic resins such as poly (meth) acrylate, polyester resins, polyurethane resins, and epoxy groups. Polyolefin resin modified by acid or acid anhydride group, olefin-acrylic copolymer resin, olefin-acrylic copolymer resin modified by epoxy group or acid anhydride group, polyester elastomer, polyamide elastomer, polyolefin Elastomers and resin plasticizers can be used.

Specific examples of resin-based plasticizers suitable as thermoplastic resins other than polylactic acid-based resins include polyester-based plasticizers such as polypropylene glycol sebacate, polyalkylene ether-based plasticizers, ether-ester-based plasticizers, and acrylate-based plasticizers. Plasticizers can be used. Among such plasticizers, from the viewpoint of maintaining the biodegradability of the entire film, the resin-based plasticizer preferably has biodegradability. Further, from the viewpoint of the bleed-out resistance of the plasticizer and the heat resistance and blocking resistance of the film, the resin-based plasticizer is, for example, a normal temperature (20 ° C. ± 15 ° C.) such as polyethylene glycol having a number average molecular weight of 1,000 or more. ) In a solid state, that is, a melting point exceeding 35 ° C. In order to suppress bleed out of the plasticizer and improve plasticization efficiency, the plasticizer solubility parameter: SP is preferably (16-23) ^1/2 MJ / m ³ , (17-21) ¹ More preferably, it is ^{/ 2} MJ / m ³ . The method for calculating the solubility parameter is described in P.A. Small, J.M. Appl. Chem. 3, 71 (1953). Furthermore, it is preferable that the melting point of the resin plasticizer is 150 ° C. or less in order to match the melt processing temperature with the polylactic acid resin which is the biodegradable resin (A).

  From the same viewpoint, the resin-based plasticizer used as the thermoplastic resin other than the polylactic acid-based resin is a block copolymer having a polyether-based segment and a polylactic acid-based segment, or a polyester-based segment and a polylactic acid-based resin. More preferably, it is a block copolymer having segments. Here, the plasticizing component in the thermoplastic resin is a polyether segment or a polyester segment. Here, the polyester-based segment means a segment made of polyester 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 proportion of the polylactic acid-based segment contained in the block copolymer plasticizer is 50% by mass or less in 100% by mass of the entire block copolymer plasticizer, so that desired flexibility can be imparted with a smaller amount of addition. Therefore, it is preferably 5% by mass or more from the viewpoint of suppressing bleed out. 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 polylactic acid-based segment of the block copolymer plasticizer is 1,200 or more, sufficient affinity between the block copolymer plasticizer and the polylactic acid-based resin that is the biodegradable resin (A) In addition, a part of the polylactic acid segment is taken into a crystal formed from the polylactic acid resin which is the biodegradable resin (A) to form a so-called eutectic, thereby producing a block copolymer. It produces an effect of anchoring the plasticizer to the polylactic acid resin as the biodegradable resin (A), and exerts a great effect on suppression of bleed out of the block copolymer plasticizer. As a result, the blocking resistance of the film is also excellent. 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 polylactic acid-type segment which a block copolymer plasticizer has is that L-lactic acid is 95-100 mass% in this segment 100 mass%, or D-lactic acid is 95-100 mass%. In particular, it is preferable because bleeding out is suppressed.

  Moreover, the porous film containing this block copolymer plasticizer is greatly superior in moisture permeability as compared with a plasticizer that is liquid at normal temperature and a plasticizer that does not form a eutectic even if it is solid at normal temperature. This is because the eutectic formed improves the hole formation efficiency by stretching described later.

  In 100% by mass of the block copolymer plasticizer, the mass ratio of the polylactic acid segment is 5 mass% to 45 mass%, and the mass ratio of the polyether segment or polyester segment is 55 mass% to 95 mass%. It is preferable that it is mass%.

  When the block copolymer plasticizer has a polyester-based segment, polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-3hydroxyhexanoate), poly (3-hydroxybutyrate) Polyesters composed of aliphatic diols such as ethylene glycol, propanediol and butanediol, and aliphatic dicarboxylic acids such as succinic acid, sebacic acid and adipic acid, etc. It is suitably used as a 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 5,000 to 20,000. By setting it as the above range, the composition constituting the film has sufficient moisture permeability and elongation at break, and when the composition containing the biodegradable resin (A) is used, the melt viscosity is at an appropriate level. And processing such as discharge and stretching during film formation can be stabilized.

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

  Moreover, it is preferable that a block copolymer plasticizer has a polyether-type segment from a viewpoint of the softness | flexibility of a porous film, and bleed-out resistance. Furthermore, it is more preferable to have a segment made of polyalkylene ether as the polyether segment because it can impart desired flexibility with a smaller amount of addition and contributes to the improvement of moisture permeability of the porous film because it is a hydrophilic component. Specific examples of the polyether segment include polyalkylene ether segments made of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol / polypropylene glycol copolymer, and the like. Among these, from the viewpoint of improving flexibility and moisture permeability, a polyalkylene ether segment made of polyethylene glycol is most preferable.

  Next, a block copolymer plasticizer that employs polyethylene glycol having a hydroxyl terminal at both ends as the polyether segment (hereinafter, polyethylene glycol is referred to as PEG) will be described in detail.

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 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 )%.

In addition, when isolate | separating a block copolymer plasticizer from a film and evaluating the number average molecular weight of each segment in a block copolymer plasticizer, it can carry out as follows. As a method for separating the block copolymer plasticizer from the film, for example, the film is uniformly dissolved in an appropriate good solvent such as chloroform and then dropped into an appropriate poor solvent such as water or a water / methanol mixed solution. The block copolymer plasticizer is obtained by removing the precipitate by filtration and evaporating the solvent of the filtrate. The block copolymer plasticizer thus separated is measured for number average molecular weight (hereinafter referred to as M) using gel permeation chromatography (GPC). Moreover, a polylactic acid segment, a polyether-type segment, and / or a polyester-type segment are specified by ¹ H-NMR measurement. The molecular weight of one polylactic acid segment contained in the block copolymer is M × {1 / (number of polylactic acid segments in one molecule)} × (I _PLA × 72) / [(I _PE × UM _PE / N _PE ) + (I _PLA × 72)]. Here, I _PLA is the signal integral intensity in ¹ H-NMR measurement derived from hydrogen of the methine group of the PLA main chain, and I _PE is ¹ H-NMR derived from the polyether segment and / or the polyester segment. Indicates the signal integration intensity in the measurement. Moreover, UM _PE is the molecular weight of the monomer unit of a polyether-type segment and / or a polyester-type segment, _NPE is a polyether-type segment and / or polyester-type segment in ¹ H-NMR measurement corresponding to _IPE The number of chemically equivalent protons that give a signal. The number average molecular weight of the polyether-based segment and / or the polyester-based segment can be calculated by M− (number average molecular weight of polylactic acid segment) × (number of polylactic acid segments in one molecule).

Although content of biodegradable resin (A) in 100 mass% of all the components of the porous film of this invention is not specifically limited, It is preferable that it is 30-99 mass%, and it is more preferable that it is 35-90 mass%. Preferably, it is 40-80 mass%, More preferably, it is 45-70 mass%.

  When the porous film of the present invention contains a polylactic acid resin, the content of the polylactic acid resin in 100% by mass of all components of the porous film is preferably 5 to 90% by mass, and 10 to 60% by mass. More preferably, it is more preferably 12 to 30% by mass.

  When the porous film of the present invention contains a thermoplastic resin other than the polylactic acid-based resin, the content of the thermoplastic resin other than the polylactic acid-based resin in 100% by mass of the total components of the porous film is moisture permeable, water resistant, and decomposed. From a viewpoint of property, it is preferable that it is 10-80 mass%, It is more preferable that it is 15-50 mass%, It is especially preferable that it is 20-45 mass%.

(Combination of thermoplastic resins other than polylactic acid resin)
In the porous film of the present invention, the resin to be combined as a thermoplastic resin other than these polylactic acid-based resins is not particularly limited, and a resin group other than the polylactic acid-based resin can be combined. Among these, from the viewpoint of improving moisture permeability, shrinkage resistance with time and elongation at break, a combination of various resin plasticizers and thermoplastic resins other than resin plasticizers is preferable, and both are biodegradable. More preferably, it has. Furthermore, as a resin plasticizer, at least one selected from the group consisting of 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 A combination of two resins and at least one resin selected from the group consisting of aliphatic polyester resins and aliphatic aromatic polyester resins is particularly preferable as the thermoplastic resin other than the resin-based plasticizer.

  Suitable for combination with a block copolymer having a polyether-based segment and a polylactic acid-based segment and at least one resin selected from the group consisting of a block copolymer having a polyester-based segment and a polylactic acid-based segment The aliphatic polyester resin used is a polybutylene succinate resin, and the aliphatic aromatic polyester resin is poly (butylene adipate terephthalate). In particular, polybutylene succinate resins are most preferable from the viewpoint of compatibility with polylactic acid resins and resin plasticizers.

When a thermoplastic resin other than a polylactic acid-based resin combines various resin-based plasticizers with a thermoplastic resin other than a resin-based plasticizer, the mass ratio is (various resin-based plasticizer / resin-based Thermoplastic resins other than plasticizers) = (5/95) to (95/5) are preferable, (10/90) to (80/20) are more preferable, and (20/80) to More preferably (60/40).

(Filler (B))
It is important that the porous film of the present invention contains 1 to 70% by mass of the filler (B) in 100% by mass of all components of the porous film. When the filler (B) is less than 1% by mass, the film has poor moisture permeability. When the filler (B) exceeds 70% by mass, the film has poor elongation at break.

  Further, the content of the filler (B) is more preferably 10 to 65% by mass, and further preferably 20 to 60% by mass, in 100% by mass of all the components of the porous film of the present invention. It is especially preferable that it is -55 mass%.

  The filler (B) 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 such a filler (B), an inorganic filler and / or an organic filler can be used.

  Examples of inorganic fillers include various carbonates such as calcium carbonate, various sulfates such as barium sulfate, zinc oxide, silicon oxide (silica), various oxides such as titanium oxide and alumina, and other such as aluminum hydroxide. Uses hydroxides, silicate minerals, hydroxyapatite, mica, talc, kaolin, clay, montmorillonite, various composite oxides such as zeolite, various phosphates such as calcium phosphate, various salts such as lithium chloride and lithium fluoride can do.

  Examples of organic fillers include oxalates such as calcium oxalate, terephthalates such as calcium, manganese, and magnesium, and vinyl monomers such as divinylbenzene, styrene, acrylic acid, and methacrylic acid. Fine particles, organic fine particles such as polytetrafluoroethylene, cellulosic powders such as wood powder and pulp powder, rice husks, wood chips, oats, chips such as waste paper pulverized materials, clothing pulverized materials, cotton fibers, hemp fibers Plant fibers such as bamboo fibers, animal fibers such as silk and wool, synthetic fibers such as polyester fibers, nylon fibers, and acrylic fibers can be used.

  Among these fillers, calcium carbonate, barium sulfate, silicon oxide (silica), titanium oxide, mica, talc are used from the viewpoints of improving the moisture permeability of the film, maintaining mechanical properties such as strength and elongation, and reducing costs. , Kaolin, clay, montmorillonite and zeolite are preferred, and calcium carbonate is particularly 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 of the filler (B) to 0.01 μm or more, it becomes possible to fill the film with a high amount of the filler. As a result, the film has a high potential for increasing the porosity and moisture permeability of the film. 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 for increasing the porosity and moisture permeability of the film. The average particle diameter of the filler (B) 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 (B) used for the porous film of the present invention can be treated with a surface treatment agent as necessary. As the surface treatment agent used, phosphate ester compounds, fatty acids, resin acids, surfactants, fats and oils, waxes, carboxylic acid coupling agents, silane coupling agents, titanate coupling agents, polymer surface treatment agents Etc. can be used. By using the compound treated with these surface treatment agents as the filler (B), the affinity with the biodegradable resin (A) is improved, and it is effective in suppressing the aggregation of the filler and improving the dispersibility. The filler can be uniformly dispersed in the resin composition. As a result, since pores are uniformly formed during stretching, a film excellent in moisture permeability, shrinkage resistance with time, and elongation at break can be obtained.

  Among these, the surface treatment agent used in the filler (B) used in the porous film of the present invention is more preferably a phosphate ester compound and / or a fatty acid.

  When at least one of an aliphatic polyester resin or an aliphatic aromatic polyester resin is used as the thermoplastic resin in addition to the polylactic acid resin as the biodegradable resin (A), the biodegradable resin (A) From the viewpoint of improving affinity, it is preferable to use a phosphate ester compound as the surface treatment agent used in the filler (B) used in the porous film of the present invention.

(Organic lubricant)
It is preferable that the porous film of this invention contains 0.1-5 mass% of organic lubricants in 100 mass% of the whole film from a viewpoint of the blocking prevention of a compound pellet or a film.

  Examples of the organic lubricant include fatty acid amides such as stearamide and ethylene bis stearamide.

(Additive)
The porous film of the present invention may contain additives other than those described above as long as the effects obtained by the present invention are not impaired. For example, known UV stabilizers, anti-coloring agents, matting agents, antibacterial agents, deodorants, flame retardants, weathering agents, antistatic agents, antioxidants, ion exchange agents, tackifiers, antifoaming agents , Coloring pigments, dyes, crystal nucleating agents, and the like.

  In producing the porous film of the present invention, a polymer chain extender such as styrene-methyl (meth) acrylate-glycidyl methacrylate copolymer may be added for the purpose of improving the melt viscosity. Further, when the porous film of the present invention is produced for the purpose of reducing the hydrolysis rate, a polymer terminal blocking agent such as a carbodiimide compound may be added.

(Porosity)
It is important that the porous film of the present invention has a porosity of 5 to 80%. When the porosity is less than 5%, the moisture permeability is insufficient, and when the porosity exceeds 80%, the elongation at break of the film is insufficient. The porosity is more preferably 10 to 70%, still more preferably 20 to 60%. The “porous” in the porous film of the present invention means that the porosity is 5% or more. That is, in the present invention, a film having a porosity of 5% or more is referred to as a porous film.

As a method for setting the porosity to 5 to 80%, the filler (B) should have the above-mentioned preferable content, a thermoplastic resin other than the polylactic acid-based resin is contained, and the type and content thereof are In the manufacturing method described later, it is preferable to set the magnification in the stretching step within a preferable range, and in the casting step, set the molten resin film angle described below to a preferable range in the manufacturing method described below. More preferred is a method of combining a plurality of these methods, and still more preferred is a method of combining all of these methods.

(Heat shrinkage)
It is preferable that the porous film of the present invention is excellent in shrinkage resistance with time, that is, the dimensional change of the film after film formation is small. This is for maintaining the appearance of the roll wound with the film and the unwinding property of the film from the roll. Furthermore, when applying heat to process the porous film, if the dimensional change is too large, wrinkles and tears may occur.

(The heat shrinkage rate of the porous film 1)
As a measure of the shrinkage resistance with time, the porous film 1 of the present invention has a heat shrinkage ratio of 0 to 10 in the stretching direction (the stretching direction means the stretched direction) after being stored at 50 ° C. for 24 hours. It is important that it is −5 to 5% in the orthogonal direction (the orthogonal direction means a direction orthogonal to the stretching direction). The direction in which the film is stretched is referred to as the stretching direction, and the direction orthogonal to the stretching direction is referred to as the orthogonal direction.

  By making the thermal shrinkage rate 10% or less in the stretching direction and 5% or less in the orthogonal direction, 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. Furthermore, it is possible to suppress the generation of tears and wrinkles during heating for compositing the porous film 1. Moreover, by making it 0% or more with respect to the stretching direction and −5% or more with respect to the orthogonal direction, it is possible to suppress deterioration of the winding shape due to the film after winding being slackened in the length direction over time. Here, when the shrinkage rate is less than 0 (negative value), it means that the film is stretched. The thermal shrinkage in the stretching direction is more preferably 0 to 7%, and further preferably 0 to 5%. Further, the thermal shrinkage in the orthogonal direction is more preferably −3 to 3%, and further preferably −2 to 2%.

  As a method for setting the heat shrinkage rate in the stretching direction to 0 to 10% and the heat shrinkage rate in the orthogonal direction to -5 to 5%, the filler (B) is made to have the above-mentioned preferable content, polylactic acid type A thermoplastic resin other than the resin is contained, and the type and content thereof are preferably set as described above, the temperature in the heat treatment step is set in a preferable range in the manufacturing method described later, and the magnification in the stretching step is set in a preferable range. In the casting step, it is mentioned that the molten resin film angle described later is within a preferable range. More preferred is a method of combining a plurality of these methods, and still more preferred is a method of combining all of these methods.

(The heat shrinkage rate of the porous film 2)
As a measure of the shrinkage resistance with time, the porous film 2 of the present invention has a direction in which the thermal shrinkage rate becomes maximum after being stored at 50 ° C. for 24 hours (hereinafter, the direction in which the thermal shrinkage rate is maximized is referred to as direction A, Regarding the direction perpendicular to the direction A is referred to as direction B), it is important that the heat shrinkage rate is 0 to 10% and the heat shrinkage rate in the direction B is −5 to 5%. The term “maximum direction of thermal shrinkage” as used herein refers to the direction in which the thermal shrinkage rate of the film is measured by changing the direction every 10 ° in the film plane and the thermal shrinkage rate is maximized. By setting the thermal shrinkage rate to 10% or less in the direction A and 5% or less in the direction B, 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. Furthermore, it is possible to suppress the generation of tears and wrinkles during heating for compositing the porous film 2. In addition, when the heat shrinkage rate in the direction A is 0% or more, and the heat shrinkage rate in the direction B is −5% or more, the wound film is loosened in the length direction over time. Deterioration can be suppressed. Here, when the shrinkage rate is less than 0 (negative value), it means that the film is stretched. The heat shrinkage rate in the direction A is more preferably 0 to 7%, and further preferably 0 to 5%. Further, the thermal contraction rate in the direction B is more preferably −3 to 3%, and further preferably −2 to 2%.

  As a method for setting the heat shrinkage rate in the direction A to 0 to 10% and the heat shrinkage rate in the direction B to -5 to 5%, the filler (B) is made to have the above-mentioned preferable content, polylactic acid type A thermoplastic resin other than the resin is contained, and the type and content thereof are preferably set as described above, the temperature in the heat treatment step is set in a preferable range in the manufacturing method described later, and the magnification in the stretching step is set in a preferable range. In the casting step, it is mentioned that the molten resin film angle described later is within a preferable range. More preferred is a method of combining a plurality of these methods, and still more preferred is a method of combining all of these methods.

(Elongation at break)
In the porous film of the present invention, it is important that the elongation at break in the orthogonal direction or direction B is 15% or more. When the elongation at break in the orthogonal direction or direction B is 15% or more, film breakage and defects (holes) are less likely to occur during film formation, and the film formability is good, and the workability is also good. The elongation at break in the orthogonal direction or direction B is more preferably 20% or more. The upper limit of the elongation at break in the orthogonal direction or direction B is not particularly limited, but is 1000% or less due to the characteristics of the resin used and the uniaxially stretched product.

  As a method for setting the elongation at break in the orthogonal direction or direction B to 15% or more, the filler (B) is made the preferable content described above, and contains a thermoplastic resin other than the polylactic acid resin, In the manufacturing method to be described later, the type and content are preferably described above, the temperature in the heat treatment step is in a preferable range, the magnification in the stretching step is in a preferable range, For example, the molten resin film angle may be within a preferable range. More preferred is a method of combining a plurality of these methods, and still more preferred is a method of combining all of these methods.

(Degradability)
The film having the biodegradable resin is roughly divided into the following two steps to be finally decomposed into water and carbon dioxide.

1) The film collapses and the shape becomes fine (in a garbage bag once collected after use in a desired application),
2) Hydrolysis and enzymatic degradation proceed in compost and soil, and finally it is decomposed into water and carbon dioxide by microbial metabolism.

  The factor determining the degradability of 2) mainly depends on the molecular structure of the biodegradable resin. In the present invention, 1) was found that the tear propagation resistance and the tensile strength of the film are important factors.

  In addition, the degradability as used in the field of this invention is mentioned later for details, but after using a film for a desired use, it decomposes | disintegrates easily, and also means that biodegradability accelerates in connection with it.

(Tear propagation resistance)
The porous film of the present invention preferably has a tear propagation resistance in the stretching direction or direction A of 1,000 mN / mm or less. When the tear propagation resistance in the stretching direction or direction A exceeds 1,000 mN / mm, the decomposability may be insufficient. The tear propagation resistance in the stretching direction or direction A is more preferably 800 mN / mm or less. The lower limit of the tear propagation resistance in the stretching direction or direction A is not particularly limited, but is practically 5 mN / mm or more.

  As a method for setting the tear propagation resistance in the drawing direction or direction A to 1,000 mN / mm or less, the filler (B) is made the above-mentioned preferable content, and a thermoplastic resin other than the polylactic acid resin is contained. In the production method described later, the type and content are preferably described above, the temperature in the heat treatment step is set to a preferable range, the magnification in the stretching step is set to a preferable range, in the casting step, It is mentioned to make the below-mentioned molten resin film angle into a preferable range. More preferred is a method of combining a plurality of these methods, and still more preferred is a method of combining all of these methods.

(Tensile strength)
The porous film of the present invention preferably has a tensile strength in the orthogonal direction or direction B of 15 MPa or less. If the tensile strength in the orthogonal direction or direction B exceeds 15 MPa, the decomposability may be insufficient. The tensile strength in the orthogonal direction or direction B is more preferably 10 MPa or less. The lower limit of the tensile strength in the orthogonal direction or direction B is not particularly limited, but is practically 0.5 MPa or more.

  As a method for setting the orthogonal direction or the tensile strength in the direction B to 15 MPa or less, the filler (B) should have the above-mentioned preferable content, a thermoplastic resin other than the polylactic acid-based resin is contained, the type and In the manufacturing method described later, the content in the heat treatment step is set to a preferable range, the magnification in the stretching step is set in a preferable range, and the cast resin is used in the molten resin film described later. It is mentioned that an angle is made into a preferable range. More preferred is a method of combining a plurality of these methods, and still more preferred is a method of combining all of these methods.

(Moisture permeability)
The porous film of the present invention preferably has a moisture permeability of 500 g / (m ² · day) or more. If the moisture permeability is less than 500 g / (m ² · day), the moisture permeability may be insufficient, and condensation may occur on the high humidity side of the porous film. The moisture permeability is more preferably 700 g / (m ² · day) or more, and still more preferably 1,000 g / (m ² · day) or more. The upper limit of moisture permeability is not particularly limited, but is 10,000 g / (m ² · day) or less from the characteristics of the resin used and the uniaxially stretched product.

As a method for setting the moisture permeability to 500 g / (m ² · day) or more, the filler (B) is made to have the preferred content described above, a thermoplastic resin other than the polylactic acid-based resin is contained, and its type In the production method to be described later, the temperature in the heat treatment step is set to a preferable range, the ratio in the stretching step is set to a preferable range, and in the casting step, the molten resin described later is used. For example, the film angle may be within a preferable range. More preferred is a method of combining a plurality of these methods, and still more preferred is a method of combining all of these methods.

(Water pressure resistance)
The porous film of the present invention preferably has a water pressure resistance of 400 mm or more. When the water pressure resistance is less than 400 mm, liquid water may pass through the porous film when used for applications such as rainwear that come into contact with water. The water pressure resistance is more preferably 700 mm or more, and even more preferably 1,000 mm or more. The upper limit of the water pressure resistance is not particularly limited, but is 10,000 mm or less from the characteristics of the resin used and the uniaxially stretched product.

  As a method for setting the water pressure resistance to 400 mm or more, the filler (B) is set to the above-described preferable content, the manufacturing method described later, the magnification in the stretching step is set to a preferable range, in the casting step The range of the molten resin film angle described below is preferably set. More preferred is a method of combining a plurality of these methods, and still more preferred is a method of combining all of these methods.

(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. By setting the film thickness to 200 μm or less, the film has excellent flexibility and moisture permeability. The film thickness is more preferably 7 to 100 μm, further preferably 10 to 50 μm, and particularly preferably 12 to 40 μm.

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

  The polylactic acid resin that is the biodegradable 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 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.

  In obtaining a composition (raw material) used for producing the porous film of the present invention, that is, a composition containing other components such as a biodegradable resin (A), a filler (B), or 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, but this is a production method that does not require steps such as dissolution and solvent removal and has high productivity. It is preferable to employ a melt-kneading method for producing a composition by melt-kneading each component. 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 180 ° C. to 220 ° C. in order to prevent the biodegradable resin (A) from being deteriorated.

  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. for 6 hours. It is preferable that the water content be 500 ppm (mass basis) or less, preferably 200 ppm (mass basis) or less by drying as described above. Furthermore, it is preferable to reduce the amount of lactic acid oligomer components in the composition containing a polylactic acid-based resin or the like by vacuum drying under a high vacuum with a degree of vacuum of 10 Torr or less. By reducing the amount of water in the composition containing polylactic acid resin and the like to 500 ppm (mass basis) or less, the amount of the lactic acid oligomer component can be prevented from hydrolysis during melt-kneading, thereby preventing a decrease in molecular weight. It is also preferable because the melt viscosity in the film forming process can be set to an appropriate level and the film forming process can be stabilized. Also, from the same point of view, when pelletizing or melt-extrusion / film formation once, a twin-screw extruder with a vacuum vent hole is used and melt extrusion is performed while removing volatiles such as moisture and low molecular weight substances. It is preferable to do.

  Although the porous film 1 or 2 of this invention is not limited to this, For example, the process of manufacturing an unstretched film using the composition obtained by the above-mentioned method, the process of extending | stretching a film in one direction (Hereinafter referred to as the stretching step) and the step of heating the film (hereinafter referred to as the heat treatment step) can be obtained in this order.

  As a method for producing an unstretched film, an inflation method or a tubular method can be applied, but a T-die casting method having a step of discharging and casting a molten resin (hereinafter referred to as a casting step) is preferable. In the case of the T die casting method, it is possible to orient and arrange the molten resin and particles by adjusting the casting position as described later, and the resulting porous film has shrinkage with time and breakage point. It is because it is excellent in the balance of elongation and moisture permeability. That is, in the manufacturing method of the porous film of this invention, it is preferable that it is a manufacturing method which has a casting process, an extending process, and a heat treatment process in this order.

  Regarding the stretching process, typical stretching in the length direction is roll stretching utilizing the difference in peripheral speed of the roll, and typical stretching in the width direction is gripping the width direction with a clip and stretching the clip. It is tenter stretching that runs on the rail along the pattern. In the present invention, any of the methods described above may be used for stretching the film in one direction, but from the viewpoint of productivity and simplicity of the apparatus configuration, the method is preferably roll stretching in the longitudinal direction. .

It is important that the porous film 1 of the present invention is stretched in only one direction (hereinafter, the stretched direction is referred to as a stretching direction, and the direction orthogonal to the stretching direction is referred to as the orthogonal direction). By stretching the film in one direction, peeling occurs at the interface between the biodegradable resin (A) and the filler (B), whereby a porous film having excellent moisture permeability can be obtained. If the film is stretched in two or more directions (for example, stretched in one direction and then in the orthogonal direction), the production apparatus becomes complicated and the cost increases, and film breaks occur frequently during production. It may become impossible to collect a stable porous film. Furthermore, the elongation at break of the obtained film may be small. In addition, the strength at break is too high, and the above-described decomposability may be deteriorated.

  The porous film 2 of the present invention is preferably stretched in only one direction (hereinafter, the stretched direction is referred to as the stretching direction, and the direction orthogonal to the stretching direction is referred to as the orthogonal direction). By stretching the film in one direction, peeling occurs at the interface between the biodegradable resin (A) and the filler (B), whereby a porous film having excellent moisture permeability can be obtained. If the film is stretched in two or more directions (for example, stretched in one direction and then in the orthogonal direction), the production apparatus becomes complicated and the cost increases, and film breaks occur frequently during production. It may become impossible to collect a stable porous film. Furthermore, the elongation at break of the obtained film may be small. In addition, the strength at break is too high, and the above-described decomposability may be deteriorated. When extending | stretching only to one direction, generally the direction A corresponds with an extending | stretching direction.

  As for the heat treatment step, roll heat treatment or tenter heat treatment is possible. From the viewpoint of simplicity of the apparatus configuration, it is preferable to perform roll heat treatment when performing roll stretching, and to perform tenter heat treatment when performing tenter stretching.

  When manufacturing the porous film of this invention by the T die-cast method, it carries out in the following processes, for example. 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. An unstretched 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.

  Further, in the casting step, an angle formed by a film made of molten resin discharged from the lip of the die and a vertical plane passing through the lip of the die (this angle is called a molten resin film angle) is 15 to 70 °. It is preferable to cast as follows. The above situation will be briefly described with reference to FIG. Usually, when manufacturing a film by the T-die casting method, the molten resin film angle is generally set to 0 to 10 ° in order to reduce the thickness unevenness of the film. On the other hand, in the present invention, by forming the molten resin film at an angle of 15 to 70 ° in the casting process, the porous film has excellent moisture permeability while balancing the shrinkage with time and the elongation at break. It was found that a film was obtained. This is because by setting the molten resin film angle to 15 to 70 °, the biodegradable resin (A) is oriented and easily crystallized at the time of casting. Accordingly, the filler (B) is also biodegradable resin (A ) In the orientation / crystallized region, and as a result, holes are easily formed even at a relatively low draw ratio. If the porous film contains a thermoplastic resin other than the polylactic acid-based resin and the type and content thereof are the above-mentioned preferable ones, the filler (B) is more easily arranged. Promoted. When the molten resin film angle exceeds 70 °, castability is deteriorated, and a film having a uniform width and thickness may not be produced. The molten resin film angle in the casting step is more preferably 25 to 60 °, and further preferably 30 to 50 °.

  In order to set the molten resin film angle in the casting process to 15 to 70 °, in addition to adjusting the position of the wire electrode for bringing the film made of the molten resin into close contact with the cooling drum, the position of the base is the center of the cooling drum. Rather than moving in the drum rotation direction.

  When performing roll stretching in the machine direction on the unstretched film thus obtained, for example, the following method can be applied. First, the temperature is raised to a temperature at which longitudinal stretching is performed by conveying an unstretched film 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 30 to 90 ° C, more preferably 30 to 75 ° C, and further preferably 40 to 70 ° C. The unstretched film heated in this way is stretched in one or two or more stages in the longitudinal direction of the film using a difference in peripheral speed between heating rolls. The stretching ratio in the stretching step (here, the stretching ratio means the product of the stretching ratios in each stage when stretching in multiple stages) is preferably 1.5 to 4.5 times, more preferably. Is 2.5 to 4.0 times.

Next, this stretched film is heat-treated under tension with a fixed length in the width direction or while relaxing in the width direction. A preferable heat treatment temperature in the heat treatment step is 30 to 75 ° C, more preferably 40 to 70 ° C. Usually, the heat treatment temperature for reducing the thermal shrinkage of the film is a high temperature exceeding 90 ° C. On the other hand, in the present invention, setting the heat treatment temperature in the range of 30 to 75 ° C. makes the elongation at break in the orthogonal direction while the thermal shrinkage rate in the stretching direction of the obtained porous film is 0 to 10%. It was found that the content is preferably 15% or more. This is because if the heat treatment temperature is too high, crystallization in a state where the molecules are oriented proceeds too much, thereby reducing the elongation at break in the orthogonal direction. The heat treatment time is preferably in the range of 0.2 to 30 seconds, but is not particularly limited. Moreover, when performing relaxation in the stretching direction after stretching, the relaxation rate is preferably 1 to 10%, more preferably 3 to 5%.

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) 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 240 ° C. and 5 MPa, and then quenched with water at 25 ° C. to prepare a sheet in which the pores were completely erased. 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
Using the porosity value, evaluation was made according to the following criteria.
○: 20% or more and 60% or less △: 10% or more and less than 20%, or more than 60% and 70% or less Δ △: 5% or more and less than 10%, or more than 70% and 80% or less ×: less than 5%, or Over 80%.

(2) Thermal contraction rate When measuring the thermal contraction rate in the stretching direction, a sample was cut into a strip shape having a length of 150 mm and a width of 10 mm in the stretching direction, and a marked line between 100 mm was inserted in the length direction. This sample was treated for 24 hours in a dry heat oven with the interior maintained at 50 ° C., then the dimension between the marked lines was measured, and the thermal shrinkage was calculated according to the following formula. The measurement was performed 5 times per level, and the heat shrinkage rate in the stretching direction was determined from the average value of the 5 measurements.
Shrinkage rate (%) = [{(size before shrinkage) − (size after shrinkage)} / (size before shrinkage)] × 100
Evaluation was made based on the following criteria using the value of thermal shrinkage in the stretching direction.
○: 0% or more and 7% or less Δ: Over 7% and 10% or less ×: Less than 0% or over 10%

  The thermal shrinkage rate in the orthogonal direction was determined by the same method.

Evaluation was made based on the following criteria using the value of the heat shrinkage rate in the orthogonal direction.
○: −3% to 3% Δ: −5% to less than −3%, or more than 3% and 5% or less ×: less than −5%, or more than 5%

  Further, when determining the direction in which the heat shrinkage rate is maximized, any direction is set to 0 °, and the direction is changed every 10 ° from −90 ° to 90 ° in the film plane, and the heat shrinkage rate is similarly set. Was measured, and the heat shrinkage rate in the direction (direction A) in which the heat shrinkage rate was the maximum and the heat shrinkage rate in the direction perpendicular to the heat shrinkage rate (direction B) were obtained.

Using the value of the heat shrinkage rate in the direction A, the following criteria were used for evaluation.
○: 0% or more and 7% or less Δ: Over 7% and 10% or less ×: Less than 0% or over 10%

Moreover, it evaluated on the following references | standards using the value of the thermal contraction rate about the direction B. FIG.
○: −3% to 3% Δ: −5% to less than −3%, or more than 3% and 5% or less ×: less than −5%, or more than 5%

(3) Elongation at break The elongation at break in the orthogonal direction or direction B was measured in an atmosphere of room temperature 23 ° C. and relative humidity 65% by using TENSILON (registered trademark) UCT-100 manufactured by Orientech.

  Specifically, a sample is cut out in a rectangular shape having a length of 150 mm and a width of 10 mm in the orthogonal direction, and the distance between the initial tensile chucks is 50 mm and the tensile speed is 200 mm / min, according to the method defined in JIS K-7127 (1999). Ten measurements were performed, and the average value was defined as the elongation at break.

Using the value of the elongation at break, the evaluation was made according to the following criteria.
○: 20% or more Δ: 15% or more and less than 20% ×: less than 15%

Moreover, about the direction B, it measured similarly and evaluated on the following references | standards using the value of the breaking elongation.
○: 20% or more Δ: 15% or more and less than 20% ×: less than 15%

(4) Tear propagation resistance The tear propagation resistance in the stretching direction was measured in an atmosphere at a room temperature of 23 ° C. and a relative humidity of 65%.

  Specifically, a sample is cut into a strip shape having a length of 150 mm and a width of 40 mm in the stretching direction, a 75 mm cut is made in the center of the width of the strip sample, and the trouser of JIS K7128-1 (1998) at a speed of 200 mm / min. In accordance with the tearing method, the stretching direction was measured five times, and the average value was taken as the tear propagation resistance.

  The tear propagation resistance in the present invention is the “tear strength” (the tear strength (mN) of the test piece divided by the thickness (mm) of the test piece) in the trouser tear method of JIS K7128-1 (1998). Thing).

  Moreover, the measurement was similarly performed about the direction A.

(5) Tensile strength Tensile strength in the orthogonal direction was measured in an atmosphere of 23 ° C. and 65% relative humidity using TENSILON UCT-100 manufactured by Orientec.

  Specifically, a sample is cut out in a rectangular shape having a length of 150 mm and a width of 10 mm in the orthogonal direction, and the distance between the initial tensile chucks is 50 mm and the tensile speed is 200 mm / min, according to the method defined in JIS K-7127 (1999). The average value was taken as the tensile strength.

  Moreover, the measurement was similarly performed about the direction B. FIG.

(6) Moisture permeability The moisture permeability (g / (m ² · day)) was measured with a constant temperature and humidity apparatus set at 25 ° C. and 90% RH according to the method defined in JIS Z0208 (1976).

(7) Water pressure resistance The water pressure resistance (mm) was measured according to the method defined in JIS L1092 (2009), Method A (low water pressure method). The film, packing, wire mesh, and packing were placed in order from the bottom between the clamps for fixing the film, and the water pressure resistance was measured with the whole being sandwiched between the clamps. The wire mesh used was plain weave, mesh spacing of 4 mm, and wire diameter of 1 mm. Moreover, since the upper limit of the measured value was 1,500 mm, when it exceeded 1,500 mm, it was described as “1500 <”.

[Biodegradable resin (A) (polylactic acid resin)]
(A1)
Polylactic acid resin, mass average molecular weight = 200,000, D-form content = 1.4 mol%, melting point = 166 ° C., biodegradability = 99% (40 days, JIS K6955-2 (2010))
(A2)
Polylactic acid resin, mass average molecular weight = 200,000, D-form content = 12.0 mol%, melting point = none, biodegradability = 99% (40 days, JIS K6953-2 (2010))
In addition, said mass mean molecular weight was measured using Japan Waters Co., Ltd. product Waters2690, polystyrene as a standard, column temperature of 40 degreeC, and the chloroform solvent.

  The above melting point was determined by heating a polylactic acid resin in a hot air oven at 100 ° C. for 24 hours, using a differential scanning calorimeter RDC220 manufactured by Seiko Instruments Inc., and setting 5 mg of a sample in an aluminum tray. It was determined as the peak temperature of the crystal melting peak when the temperature was raised from 250C to 250C at a heating rate of 20C / min.

[Biodegradable resin (A) (thermoplastic resin other than polylactic acid resin)]
(A3)
Polybutylene succinate resin (trade name “GSPla” (registered trademark) AZ91T, manufactured by Mitsubishi Chemical Corporation), biodegradability = 85% (40 days, JIS K6953-2 (2010))
(A4)
Poly (butylene adipate terephthalate) resin (BASF, trade name “Ecoflex” F Blend C1200), biodegradability = 90% (80 days, JIS K6953-2 (2010))
(A5)
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, A5 of a block copolymer plasticizer having polylactic acid segments 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. Biodegradation = 80% (300 days, JIS K6953-2 (2010))

[Plasticizer]
(P1)
Tributyl acetyl citrate, manufactured by Pfizer, trade name “Citroflex A-4”)
[Filler (B)]
(B1)
Calcium carbonate (Ajinomoto Fine Techno Co., Ltd., trade name “Topflow H200”, average particle size: 1.7 μm, surface treatment agent: phosphate compound)
(B2)
Calcium carbonate (manufactured by Sankyo Seimitsu Co., Ltd., trade name “E # 2010”, average particle size: 1.8 μm, surface treatment agent: stearic acid)
Example 1
Biodegradable resin (A1) 4% by mass, Biodegradable resin (A2) 11% by mass, Biodegradable resin (A3) 20% by mass, Biodegradable resin (A5) 15% by mass, Filler (B1) 50 The mass% mixture was subjected to a twin screw extruder with a vacuum vent of 44 mm and a cylinder diameter of 190 ° C. and a vacuum vent, melt kneaded while degassing the vacuum vent, homogenized, and 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 unstretched film. The molten resin film angle at this time was 45 °. This unstretched film is guided to a roll-type stretching machine, stretched three times in the length direction at a temperature of 40 ° C., once cooled on a cooling roll, and then heat-treated through a roll at a temperature of 60 ° C. Got. Table 1 shows the physical properties of the obtained film. In addition, the direction A and the extending | stretching direction corresponded.

(Examples 2-19, Comparative Examples 1-4, 6, 7)
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 Tables 1, 2 and 3. The physical properties of the obtained film are shown in Tables 1, 2, and 3. In all cases except for Comparative Example 1 in which stretching was not performed, the direction A and the stretching direction were the same. In Comparative Example 1, the longitudinal direction of the film was direction A.

(Comparative Example 5)
Manufacture was attempted in the same manner as in Example 1 except that the molten resin film angle was set to 80 °. However, since the molten resin film was successively perforated, broken, and varied in width, an unstretched film could not be obtained. It was.

(Comparative Example 8)
Except for changing the composition of the film as shown in Table 3, production was attempted in the same manner as in Example 1, but stretching was impossible.

  In the table, “MD” is the length direction and “TD” is the width direction. Except for Comparative Example 1 in which stretching is not performed, MD is the stretching direction and TD is the orthogonal direction.

1 base 2 lip 3 vertical plane passing through the base lip 4 film made of molten resin discharged from the base lip 5 film made of molten resin discharged from the base lip and a vertical plane passing through the base lip Angle (molten resin film angle)
6 Cooling drum

  The porous film of the present invention is mainly composed of a biodegradable resin, has a good balance between shrinkage resistance with time and elongation at break, and is excellent in moisture permeability. The porous film of the present invention includes medical and hygiene materials such as bed sheets, pillow covers, and back sheets of absorbent articles such as sanitary napkins and paper diapers; clothing materials such as rainy clothes and gloves; garbage bags and compost bags, or vegetables It can be used for packaging materials such as food bags for foods and fruits, bags for various industrial products, and the like.

Claims (10)

Including biodegradable resin (A),
In 100% by mass of all components of the porous film, 1 to 70% by mass of the filler (B) is contained,
The porosity is 5 to 80%,
It is stretched in only one direction (hereinafter, the stretched direction is referred to as the stretching direction, and the direction orthogonal to the stretching direction is referred to as the orthogonal direction)
The heat shrinkage rate in the stretching direction is 0 to 10%,
The heat shrinkage in the orthogonal direction is -5 to 5%,
A porous film having an elongation at break in an orthogonal direction of 15% or more. Including biodegradable resin (A),
In 100% by mass of all components of the porous film, 1 to 70% by mass of the filler (B) is contained,
The porosity is 5 to 80%,
The heat shrinkage rate in the direction in which the heat shrinkage rate is maximized (hereinafter, the direction in which the heat shrinkage rate is maximized is referred to as direction A, and the direction orthogonal to direction A is referred to as direction B) is 0 to 10%.
The thermal shrinkage in the direction B is -5 to 5%,
A porous film having an elongation at break in the direction B of 15% or more.   The porous film according to claim 1 or 2, wherein the tear propagation resistance in the stretching direction or direction A is 1,000 mN / mm or less, and the tensile strength in the orthogonal direction or direction B is 15 MPa or less. The porous film according to any one of claims 1 to 3, wherein moisture permeability is 500 g / (m ² · day) or more.   The porous film according to claim 1, wherein the biodegradable resin (A) is a polylactic acid resin.   The porous film according to claim 5, comprising a thermoplastic resin other than a polylactic acid resin.   The thermoplastic resin other than the polylactic acid resin is at least selected from the group consisting of 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. The porous film according to claim 6, comprising a combination of one resin and at least one resin selected from the group consisting of an aliphatic polyester-based resin and an aliphatic aromatic polyester-based resin. Porous having a process of discharging and casting a molten resin (hereinafter referred to as a casting process), a process of stretching a film in one direction (hereinafter referred to as a stretching process), and a process of heating a film (hereinafter referred to as a heat treatment process) in this order. A method for producing a film,
The method for producing a porous film according to any one of claims 1 to 7, wherein the temperature in the heat treatment step is 30 to 75 ° C.   The method for producing a porous film according to claim 8, wherein in the stretching step, the film is stretched by 1.5 to 4.5 times.   In the casting step, casting is performed such that an angle formed between a film made of a molten resin discharged from a lip of the die and a vertical plane passing through the lip of the die is 15 to 70 °. Item 10. A method for producing a porous film according to Item 8 or 9.

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