JP2008200860A - Method for producing polylactic acid resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polylactic acid resin film excellent in flexibility, transparency, heat resistance, thickness nonuniformity, adhesion, and appearance. <P>SOLUTION: In the polylactic acid resin film comprising the polylactic acid resin and a plasticizer, the plasticizer has at least a polylactic acid segment with a molecular weight of 1,200-10,000 in a molecule, polyether segments and/or polyester segments. A film making method of the film is a film making method of the polylactic acid resin by a tubular method in which first bubbles are formed by a molten resin, a resin discharged in the shape of a tube, it is cooled, after the tubular resin is taken, the film forms second bubbles through the preheating process and the orientation process, and after that, it is cooled and wound after the tubular film is taken. The temperature of the film in the preheating process is lower by 5-15°C than the glass transition temperature of the film, and the temperature of the film in the orientation process is higher by 0-20°C than the glass transition temperature of the film. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a polylactic acid resin film softened with a plasticizer. More specifically, the present invention relates to a method for producing a polylactic acid resin film having properties excellent in flexibility, transparency, heat resistance and adhesion, and appearance, particularly a method for producing a film useful as a food packaging wrap film or an agricultural sheet. Is.

  Conventionally, plastic waste has been mainly treated by incineration or landfill. However, problems such as generation and discharge of harmful by-products due to incineration, reduction of landfill sites, and environmental pollution due to illegal dumping have become apparent.

  As interest in such plastic waste disposal problems increases, research and development of biodegradable plastics that are decomposed by enzymes and microorganisms are actively conducted. In recent years, aliphatic polyester materials have attracted attention as biodegradable materials, and among these, technological development is particularly advanced for polylactic acid.

  Polylactic acid is a polymer obtained by using starch obtained from corn, potatoes, and the like as a raw material and further chemically synthesizing the produced lactic acid. Polylactic acid has excellent mechanical properties, heat resistance, and transparency among aliphatic polyesters, so research aimed at developing various molded products such as films, sheets, tapes, fibers, ropes, nonwoven fabrics, and containers. Development is actively underway. However, in applications such as wrapping films for food packaging, for example, polylactic acid is insufficient in properties such as flexibility as it is, and therefore a technique for imparting necessary properties such as flexibility and adhesion has been studied.

For example, in Patent Document 1, a film for food packaging having a water vapor transmission rate of 50 to 300 g / (m ² · 24 hr) and a thickness of 10 to 500 μm, which has a polylactic acid resin as a main component and is given flexibility by adding a plasticizer. Techniques related to this are disclosed. However, the film obtained by this technology is mainly used for maintaining the freshness of fruits and vegetables and the like in which a biaxially stretched polystyrene film or the like has been mainly used so far. Adhesion was insufficient.

  Patent Document 2 discloses a technique relating to a stretched film made of a composition containing a resin mainly composed of a lactic acid-based aliphatic polyester and a liquid additive. However, when an attempt was made to produce a stretched film in accordance with the example described in Patent Document 2, the wrapping film for food packaging has a certain level of flexibility, transparency, and heat resistance, but has insufficient adhesion. Only a film was obtained. The reason for this is that there is no technical suggestion from the viewpoint of film formation conditions, that is, the formation of a higher-order structure of the film and the accompanying film physical property control. In addition to flexibility, transparency and heat resistance, adhesion No technology has been provided to impart excellent properties to

  Further, Patent Document 3 proposes a stretched polylactic acid resin film having at least one polylactic acid segment as a plasticizer that is liquid at room temperature and using a plasticizer having a polyether-based and / or polyester-based segment. The film formed based on this document was excellent in flexibility and transparency and was quite useful for food packaging, but the inventors of the present application showed flexibility, transparency, heat resistance and adhesion, and appearance. No suggestion is given to the film forming technique and the stretching technique for achieving the target level.

On the other hand, Patent Document 4 describes a technique related to tubular stretching of a biodegradable resin film. However, the polylactic acid-based resin film of this document does not reach the level of the film having the flexibility, transparency, heat resistance and adhesiveness intended by the present inventors.
As described above, although various studies have been made in the past, it is the actual situation that the inventors have not reached the target level.
JP 7-257660 A JP 2000-26623 A International Publication No. 2004/000939 Pamphlet JP 2003-286354 A

  The problem to be solved by the present invention relates to a method for producing a polylactic acid resin film excellent in adhesion and appearance in addition to flexibility, transparency, heat resistance and thickness unevenness.

  The present invention adopts the following means in view of the above-described state of the prior art. That is, a polylactic acid resin film comprising 50 to 95% by mass of a polylactic acid resin and 5 to 50% by mass of a plasticizer with respect to a total of 100% by mass of the polylactic acid resin and the plasticizer, It is a plasticizer having one or more polylactic acid segments having a molecular weight of 1,200 or more and 10,000 or less in one molecule, and having a polyether-based segment and / or a polyester-based segment, The first bubble is formed with the molten resin from which the resin is discharged in the form of a tube from the cylindrical base, and after cooling and taking the tube-shaped resin flat, the film undergoes a preheating process and a stretching process to form a second bubble. A tubular film-forming method in which the tube-shaped film is flattened after being cooled and wound, and the film temperature in the preheating step is There wherein the film temperature of 5 to 15 ° C. lower and stretching process than the glass transition temperature of the film is 0 to 20 ° C. higher than the glass transition temperature of the film, a method of manufacturing a polylactic acid resin film is.

  According to the present invention, a polylactic acid resin film excellent in adhesion and appearance in addition to flexibility, transparency, and heat resistance can be obtained. The film can be suitably used for various applications by taking advantage of its features.

  The present invention intensively examines polylactic acid-based resin films having flexibility, transparency, heat resistance, adhesion, and appearance required for wrap films, stretch films, and the like. The present inventors have found that the above required characteristics can be satisfied by using a plasticizer and performing a specific method of stretching.

  That is, in order to impart flexibility and transparency to the polylactic acid-based resin film, the polylactic acid-based resin is used in an amount of 50 to 95% by mass and a specific plasticizer in an amount of 5 to 50% by mass. Stretching process in which the first bubble is formed with molten resin that is discharged into a tube shape, cooled, and the tube-shaped resin is flattened and taken, followed by a preheating step for preheating the film, and further stretching while heating , Forming a second bubble, and then cooling and taking up the tube-like film after flattening it, and then winding it up, and the film temperature in the preheating step is the glass temperature of the film The film forming method is characterized in that the film temperature in the stretching step is 5 to 15 ° C. lower than the transition temperature and 0 to 20 ° C. higher than the glass transition temperature of the film.

  The resin used for the polylactic acid-based resin film of the present invention is composed of 50-95% by weight of polylactic acid-based resin and 5-50% by weight of plasticizer with respect to 100% by weight of the total of polylactic acid-based resin and plasticizer. is required. More preferably, the polylactic acid resin is 60 to 90% by mass and the plasticizer is 10 to 40% by mass, more preferably the polylactic acid resin is 65 to 85% by mass and the plasticizer is 15 to 35% by mass, It is good from the viewpoint of handleability and barrier properties when used.

  When the polylactic acid-based resin is less than 50% by mass, it becomes a configuration in which polylactic acid is present in the plasticizer, and it becomes very difficult to add the plasticizer to the polylactic acid-based resin, and it can be formed as a film However, since the continuous phase in the film becomes a plasticizer, it is difficult to maintain the shape as a film, and process passability and slit processability during film production may be poor. Moreover, since it sticks to the articles | goods to package, problems, such as being unable to peel, generate | occur | produce, and it may be inferior to gas barrier property.

  In addition, when the content of the polylactic acid resin exceeds 95% by mass, the flexibility is inferior, the shape does not deform following the shape of the article or food to be packaged, and sufficient adhesion may not be obtained. Further, excessive force is required for packaging, and problems such as damage to the package may occur.

Here, the polylactic acid-based resin used in the present invention is one having L-lactic acid and / or D-lactic acid as a main component, and a component derived from lactic acid in the polymer of 70% by mass or more. Homopolylactic acid composed of L-lactic acid and / or D-lactic acid is preferably used.
The polylactic acid resin used in the present invention preferably has crystallinity. The polylactic acid-based resin has crystallinity when the polylactic acid-based resin is sufficiently crystallized under heating and then subjected to DSC (Differential Scanning Calorimetry) measurement in an appropriate temperature range. This means that the heat of crystal melting derived from the components is observed. If the polylactic acid resin used in the present invention does not have crystallinity, the volatilization, leaching, and extraction (bleed out) of the plasticizer may not be sufficiently suppressed. In general, homopolylactic acid has higher melting point and crystallinity as the optical purity is higher. The melting point and crystallinity of polylactic acid are affected by the molecular weight and the catalyst used during polymerization, but normally, homopolylactic acid having an optical purity of 98% or higher has a melting point of about 170 ° C. and a relatively high crystallinity. Further, as the optical purity is lowered, the melting point and crystallinity are lowered. For example, homopolylactic acid having an optical purity of 88% has a melting point of about 145 ° C., and homopolylactic acid having an optical purity of 75% has a melting point of about 120 ° C. It is. Homopolylactic acid with an optical purity lower than 70% does not show a clear melting point and is amorphous.

  The polylactic acid-based resin used in the present invention can be mixed with crystalline homopolylactic acid and amorphous homopolylactic acid for the purpose of imparting or improving necessary functions depending on the application to be used. In this case, the proportion of amorphous homopolylactic acid may be determined within a range that does not impair the effects of the present invention. Moreover, when it is desired to impart high heat resistance when a polylactic acid resin film is used, it is preferable that at least one of the polylactic acid resins used contains polylactic acid having an optical purity of 95% or more.

  The polylactic acid resin used in the present invention has a weight average molecular weight of usually at least 50,000, preferably 80,000 to 400,000, and more preferably 100,000 to 300,000. By setting the weight average molecular weight of the polylactic acid resin to at least 50,000, a film having excellent strength properties can be obtained when the polylactic acid resin is formed into a molded article such as a film.

  The polylactic acid resin used in the present invention may be a copolymerized polylactic acid obtained by copolymerizing other monomer components having ester forming ability in addition to L-lactic acid and D-lactic acid. Examples of copolymerizable monomer components include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid, and other hydroxycarboxylic acids, as well as ethylene glycol, propylene glycol, and butane. Compounds containing a plurality of hydroxyl groups in the molecule such as diol, neopentyl glycol, polyethylene glycol, glycerin, pentaerythritol or their derivatives, succinic acid, adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid, 2 , 6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium sulfoisophthalic acid and the like, or compounds containing a plurality of carboxylic acid groups in the molecule. As a copolymerization component of the polylactic acid resin used in the present invention, it is preferable to select a biodegradable component.

  The plasticizer used in the present invention is a plasticizer having one or more polylactic acid segments having a number average molecular weight of 1,200 or more and 10,000 or less in one molecule, and having a polyether-based and / or polyester-based segment. It is necessary to be. When the mass proportion of the polylactic acid segment component of the plasticizer is less than 50 mass% of the entire plasticizer, the plasticizer has a relatively high plasticizing efficiency, and the desired flexibility can be imparted with a smaller amount of addition. preferable.

  Furthermore, the number average molecular weight of the polylactic acid segment in one molecule of the plasticizer needs to be 1,200 or more and 10,000 or less. If the plasticizer has a polylactic acid segment of 1,200 or more, the plasticizer molecule is incorporated into a crystal formed from a polylactic acid-based resin that is a base material, so that the plasticizer molecule becomes a base. An effect of securing to the material can be produced, and the volatilization, leaching and extraction (bleed out) of the plasticizer can be suppressed. Moreover, when the number average molecular weight of the polylactic acid segment in a plasticizer is larger than 10,000, the plasticization efficiency of a plasticizer will become low and it will become difficult to provide practical softness | flexibility. More preferably, it is 2,000 or more and less than 6,000.

  The plasticizer has a polylactic acid segment containing 95% by mass or more of the component derived from L-lactic acid, or 95% by mass or more of the component derived from D-lactic acid. Extraction (bleed out) is particularly preferable because it is suppressed.

  The plasticizer used in the present invention has a polyether-based segment and / or a polyester-based segment. Flexibility can be imparted to polylactic acid by introducing polyether-based and / or polyester-based segments into the plasticizer.

  When it has a polyether-based segment, it preferably has a segment made of polyalkylene ether, and more preferably has a segment made of polyethylene glycol. When the plasticizer is a polyalkylene ether such as polyethylene glycol, polypropylene glycol or polyethylene glycol / polypropylene glycol copolymer, especially polyethylene glycol, the plasticizer has excellent plasticization efficiency because of its high affinity with polylactic acid resin. In particular, a polylactic acid resin film having a desired flexibility can be obtained by adding a small amount of a plasticizer.

  In addition, when the plasticizer used in the present invention has a segment composed of a polyalkylene ether, the polyalkylene ether segment portion tends to be easily oxidized or thermally decomposed when heated at the time of molding or the like. It is preferable to use an antioxidant such as a hindered amine or a heat stabilizer such as a phosphorus.

  In the case of having a polyester-based segment, polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate / 3-hydroxyvalerate), polycaprolactone, ethylene glycol, 1,4-butanediol, etc. And polyesters composed of aliphatic diols and aliphatic dicarboxylic acids such as succinic acid and adipic acid.

  Furthermore, the number average molecular weight of the polyether-based and / or polyester-based segments in one molecule of the plasticizer of the present invention is preferably 7000 or more and less than 20,000. By making the number average molecular weight of the polyether-based and / or polyester-based segments in one molecule of the plasticizer be 7000 or more and less than 20000, the polylactic acid-based resin laminated film has a desired flexibility, and film formation is performed. It is preferable also from the point which can be stabilized.

  In the polylactic acid-type resin film of this invention, you may contain components other than the specific plasticizer mentioned above in the range which does not impair the effect of this invention. For example, various known plasticizers, antioxidants, UV stabilizers, anti-coloring agents, matting agents, deodorants, flame retardants, weathering agents, antistatic agents, mold release agents, antioxidants, ion exchange agents Alternatively, inorganic fine particles, organic particles, and organic compounds may be added as necessary as coloring pigments.

  Known plasticizers include, for example, phthalate esters such as diethyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, di-1-butyl adipate, di-n-octyl adipate, di-n-butyl sebacate , Aliphatic dibasic acid esters such as di-2-ethylhexyl azelate, phosphate esters such as diphenyl-2-ethylhexyl phosphate and diphenyloctyl phosphate, tributyl acetylcitrate, tri-2-ethylhexyl acetylcitrate , Hydroxy polycarboxylic acid esters such as tributyl citrate, fatty acid esters such as methyl acetylricinoleate and amyl stearate, polyhydric alcohol esters such as glycerin triacetate and triethylene glycol dicaprylate, epoxidized soybean oil, Epo Shi linseed oil fatty acid butyl ester, epoxy plasticizers such as epoxy stearic octyl, polyester plasticizers such as polypropylene glycol sebacic acid ester, polyalkylene ether, ether ester type, and the like acrylate. From the viewpoint of safety, it is preferable to use a plasticizer that is approved by the US Food and Drug Administration (FDA).

  Examples of the antioxidant include hindered phenols and hindered amines. Color pigments include inorganic pigments such as carbon black, titanium oxide, zinc oxide, iron oxide, cyanine, styrene, phthalocyanine, anthraquinone, perinone, isoindolinone, quinophthalone, and quinocridone. Organic pigments such as thioindigo can be used.

  For the purpose of improving the slipperiness and blocking resistance of the film, when adding inorganic fine particles or organic particles, for example, silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate, polystyrene Particles such as polymethyl methacrylate and silicone can be used. In addition, from the viewpoint of improving transparency, it is preferable to use particles having a refractive index close to that of the polylactic acid resin used as the base material, and particles such as silica, colloidal silica, and polymethyl methacrylate are more preferable in this respect. Further, as the particles used in the polylactic acid-based resin laminated film of the present invention, it is also preferable to select naturally occurring inorganic particles or biodegradable particles.

  The average particle diameter of the particles added to the polylactic acid resin film of the present invention is not particularly limited, but is preferably 0.01 to 5 μm, more preferably 0.05 to 3 μm, and most preferably 0.08 to 2 μm. .

  Furthermore, the polylactic acid-based resin film of the present invention has an aliphatic polyester other than the polylactic acid-based polymer for the purpose of increasing or decreasing the melt viscosity or improving biodegradability. May be contained. Examples of aliphatic polyesters other than polylactic acid polymers include polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate / 3-hydroxyvalerate), polycaprolactone, ethylene glycol, 1, Examples thereof include aliphatic diols such as 4-butanediol and aliphatic dicarboxylic acids such as succinic acid and adipic acid, and aliphatic hydroxycarboxylic acids such as polyglycolic acid.

  The polylactic acid-based resin film of the present invention has at least one polylactic acid-based resin or a polylactic acid segment having a number average molecular weight of 1,200 or more and 10,000 or less in one molecule, polyether-based and / or When a component other than a plasticizer having a polyester segment is contained, it is preferable to select a component having biodegradability.

  Although the thickness of the polylactic acid-type resin film of this invention is not specifically specified, It is preferable that it is 0.1-100 micrometers, More preferably, it is 1-50 micrometers.

  The polylactic acid-based resin film of the present invention is representative of bags and the like, if necessary, within a range that does not impair the effects of the present invention, such as heat sealability, gas barrier properties such as water vapor, oxygen, and carbon dioxide, releasability, and printability. Resins with the characteristics required as packaging materials for goods and foods, and polymers and compounds with the functions described above have the functions described above from polylactic acid resins and polylactic acid resins and plasticizers to resins. A resin blended with a polymer or a compound having the same function can be coextruded to form a laminated film having other functions. Further, as the resin to be coextruded, it is preferable to use a biodegradable resin or composition from the viewpoint of the present invention. Furthermore, as a method for imparting the above characteristics, thermosetting properties such as acrylic resin, polyester resin, and silicone resin, thermoplastic resin, antistatic agent, surfactant, release agent, etc. are provided on at least one surface of the film. Examples thereof include a method of applying to the surface and a method of forming a laminated structure by bonding such as adhesion and lamination. In this case also, it is preferable to use a biodegradable resin or composition from the object of the present invention.

  The polylactic acid resin film of the present invention preferably has a tensile modulus of 0.1 to 1.5 GPa. The tensile modulus of the film can be set to a desired value mainly by adjusting the amount and type of plasticizer added in the composition, film forming conditions, and the like.

  When the tensile modulus of elasticity is greater than 1.5 GPa, the flexibility is reduced, which is not preferable because the fields in which the polylactic acid resin film can be used are reduced. When the tensile modulus is less than 0.1 GPa, the release property of the wound film is inferior, and the process passability deteriorates even in the film forming and processing process, which is not preferable.

  If the tensile modulus of the film is 0.1 to 1.5 GPa, it has sufficient flexibility, transparency and strength properties, and can be used in a wider field than before. For example, packaging materials such as wrapping films for packaging, agricultural films, industrial coating materials such as automobile coating film protection sheets, garbage bags, compost bags, industrial material applications using various soft vinyl chloride, and beverages in other molded products And cosmetic bottles, disposable cups, trays and other containers, seedling pots, flower pots, etc.

  The polylactic acid resin film of the present invention preferably has a heat resistance of 120 ° C to 230 ° C. The heat resistance of the film is evaluated by the method described in the examples. Heat resistance of 120 ° C. or higher is preferred because there are almost no problems such as adhesion to the periphery during heat treatment and blocking after film formation, and the process stability is excellent. Further, when the obtained film is used as a wrapping film for food packaging, it is preferable that even if it is touched with hot water or heat-treated with a microwave oven, the film is hardly perforated or fused to the package. .

  In the polylactic acid-based resin film of the present invention, the smaller the difference between the maximum value and the minimum value of thickness measurement (hereinafter referred to as thickness unevenness), the better, and the acceptable thickness unevenness varies depending on the application. For example, in the case of a 10 μm food wrap film, the thickness unevenness is preferably 4 μm or less, and more preferably 1 μm or less. If the thickness unevenness is bad, a defect such as tearing occurs from a thin thickness.

  Next, the manufacturing method of the present invention will be described.

  The polylactic acid production method includes a two-stage lactide method in which L-lactic acid, D-lactic acid, and DL-lactic acid (racemic) are used as raw materials to once form lactide, which is a cyclic dimer, followed by ring-opening polymerization. A one-step direct polymerization method in which the raw material is directly subjected to dehydration condensation in a solvent is known. In the present invention, when homopolylactic acid is used, it may be obtained by any production method. However, in the case of a polymer obtained by the lactide method, the cyclic dimer contained in the polymer is vaporized during molding. For example, when melt film formation, it causes cast drum stains and film surface smoothness deterioration. Therefore, the content of the cyclic dimer contained in the polymer at the stage of molding or before melt film formation is 0.3 mass. % Or less is desirable. Further, in the case of the direct polymerization method, there is substantially no problem due to the cyclic dimer, which is more preferable from the viewpoint of moldability or film forming property.

  The plasticizer used in the present invention is prepared by, for example, polymerizing a polylactic acid oligomer having a number average molecular weight of 1,200 or more and 10,000 or less by a conventional method such as a lactide ring-opening method or a lactic acid condensation polymerization method. It can be obtained by reacting a suitable amount with a compound having a polyether group and / or polyester segment having a group and forming the main component of the plasticizer. Dehydration condensation of lactic acid by adding a compound having a polymer segment as a polymerization initiator to ring-opening polymerization of lactide, or using a compound having a polyether and / or polyester segment as a main component of a plasticizer as a polymerization initiator You may add to this by superposition | polymerization. In addition, a dicarboxylic acid can be obtained by a treatment such as heat kneading in the presence of a polylactic acid oligomer having a number average molecular weight of 1,200 or more and 10,000 or less and a compound having a polyether-based and / or polyester-based segment which is a main component of a plasticizer. A bifunctional compound such as an acid anhydride compound or a diisocyanate compound may act as a chain linking agent to chemically bond them together.

  Next, a more specific example of a plasticizer having one or more polylactic acid segments having a number average molecular weight of 1,200 to 10,000 in one molecule and having a polyether-based and / or polyester-based segment explain.

A polyethylene glycol having a hydroxyl group at both ends (hereinafter, polyethylene glycol is referred to as PEG) is prepared. 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 _A parts by mass are added to w _B parts by mass of PEG having hydroxyl groups at both ends, lactide undergoes ring-opening addition polymerization at both hydroxyl groups of PEG and is sufficiently reacted. A block copolymer of type (A) -PEG (B) -PLA (A) 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 the plasticizer made of this block copolymer can be substantially determined as (1/2) × (w _A / w _B ) × M _PEG . The mass percentage of the total plasticizer of the polylactic acid segment component can be substantially determined as _{100 × w A / (w A} + w B)%. Furthermore, the mass ratio of the plasticizer component excluding the polylactic acid segment component to the entire plasticizer can be substantially calculated as 100 × w _B / (w _A + w _B )%.

  When the plasticizer contains a large amount of unreacted PEG, a reaction product with PEG in which the number average molecular weight of the terminal polylactic acid segment is less than 1,200, byproducts such as lactide oligomers, or impurities. These are preferably removed, for example, by the following purification method.

  After the synthesized plasticizer is uniformly dissolved in an appropriate good solvent such as chloroform, an appropriate poor solvent such as a water / methanol mixed solution or diethyl ether is added dropwise. Alternatively, precipitation is performed by adding a good solvent solution in a large excess of poor solvent, and the solvent is evaporated after separating the precipitate by centrifugation or filtration. After immersing the plasticizer in water, it is heated to 50 to 90 ° C. and stirred as necessary, and then the organic phase containing the plasticizer is extracted and dried to remove water. The purification method is not limited to the above, and the above operation may be repeated a plurality of times as necessary. Removing by-products such as lactide oligomers can prevent the viscosity of the polylactic acid resin from decreasing.

When a plasticizer of a PLA (A) -PEG (B) -PLA (A) type block copolymer is prepared by the method described above, the number average molecular weight of one polylactic acid segment of the prepared plasticizer is: It can be obtained by the following method. That is, based on a chart obtained by ¹ H-NMR measurement using a deuterated chloroform solution of a plasticizer, {I _PLA × (molecular weight of polylactic acid monomer unit) / (number of polylactic acid segments)} / {I _PEG × (molecular weight of PEG monomer unit) / (number of chemically equivalent protons)} × M _PEG . That is, when a PLA (A) -PEG (B) -PLA (A) type block copolymer plasticizer is prepared, {I _PLA × 72/2} / {I _PEG × 44/4} × M _PEG . However, I _PEG is the signal integral intensity derived from the hydrogen of the methylene group of the PEG main chain part, and I _PLA is the signal integral intensity derived from the hydrogen of the methine group of the PLA main chain part. In the case of synthesizing under the condition that the reaction rate of lactide at the time of plasticizer synthesis is sufficiently high and almost all lactide is ring-opening added to the PEG terminal portion, in many cases, the chart obtained by ¹ H-NMR measurement is obtained. It is preferable to determine the number average molecular weight of one polylactic acid segment of the plasticizer by the above-described method.

  In order to evaluate the number average molecular weight of the polylactic acid segment in the plasticizer from the polylactic acid-based resin film in the present invention, a method for separating the used plasticizer is, for example, an appropriate good solvent such as chloroform. After the polyester is uniformly dissolved, it is dropped into a suitable poor solvent such as water or water / methanol mixed solution, and the precipitate mainly containing the polylactic acid resin is removed by filtration or the like, and the solvent of the filtrate is volatilized and separated. Examples include a reprecipitation method for obtaining a plasticizer, but the method is not limited to this, and an appropriate method can be selected or combined depending on the plasticizer or polylactic acid resin used.

The plasticizer separated from the polylactic acid resin film for molecular weight evaluation is dissolved in a solution such as THF (tetrahydrofuran) and the number average molecular weight of the plasticizer (hereinafter referred to as plasticity) is obtained using GPC (gel permeation chromatography). The number average molecular weight of the agent is defined as M), and the polylactic acid segment, the polyether-based segment and / or the polyester-based segment are specified by ¹ H-NMR measurement or the like. By using these measurement results, the number average molecular weight of one polylactic acid segment of the plasticizer separated from the polylactic acid-based resin film for molecular weight evaluation can be determined as follows. That is, based on the chart obtained by ¹ H-NMR measurement, M × {1 / (number of polylactic acid segments)} × {I _PLA × (molecular weight of PLA monomer unit = 72)} / [(I _PEPE × UM _PEPE / N _PEPE ) + {I _PLA × (PLA monomer unit molecular weight = 72)}]. However, I _PEPE is the signal integrated intensity in ¹ H-NMR measurement derived from the polyether segment and / or the polyester segment, UM _PEPE is the molecular weight of the monomer unit of the polyether segment and / or the polyester segment, N _PEPE is the number of chemically equivalent protons that give signal integral strength among polyether-based segments and / or polyester-based segments.

  For example, a PLA (A) -PEG (B) -PLA (A) type block having one or more polylactic acid segments having a number average molecular weight of 1,200 or more and 10,000 or less in one molecule obtained by the above-described method. If a copolymer is used as a plasticizer, a polylactic acid-based resin film that has sufficient flexibility and has suppressed the volatilization, exudation, and extraction (bleed out) of the plasticizer, which could not be achieved by the prior art. A sufficient effect can be obtained in the provision.

  Further, as a method of adding the above-mentioned plasticizer to the polylactic acid resin, it can be obtained by adding and melting and kneading the plasticizer at a desired mass ratio in the molten state of the polylactic acid resin. From the viewpoint of increasing the degree of polymerization of the resin and suppressing residual low molecular weight substances such as lactide, it is preferable to add and melt knead the plasticizer after the polymerization reaction of the polylactic acid resin. The method of adding and melting and kneading the plasticizer after the polymerization reaction of the polylactic acid resin can reduce the residual low molecular weight in the polylactic acid resin, so that the resin composed of the polylactic acid resin and the plasticizer is used. It is also preferable from suppressing the decrease in molecular weight. As the addition / melt kneading of the polylactic acid resin and the plasticizer described above, for example, immediately after the completion of the polycondensation reaction, a method of adding the plasticizer to the molten polylactic acid resin and stirring and melt kneading, A method in which a plasticizer is added and mixed to a chip and then melt-kneaded in a reactor or an extruder, a method in which a plasticizer is continuously added to a polylactic acid resin with an extruder and melt-kneaded, and a high concentration of plasticizer is contained. It can be carried out by a method in which a master chip of polylactic acid resin and a homochip of polylactic acid resin are mixed and melt-kneaded with an extruder or the like.

  The method for producing a polylactic acid-based resin film according to the present invention is to form a first bubble with a molten resin in which a resin is discharged from a cylindrical die into a tube shape, cool the tube-shaped resin, and then take the film into a flat shape. A film by the tubular method that passes through a preheating step of preheating, passes through a stretching step of stretching while heating, forms a second bubble, and then cools and winds the tubular film after flattening it. It must be a manufacturing method.

  The tubular film manufacturing method is, for example, a method as described on pages 374 to 377 of “Practical Plastic Molding Encyclopedia” issued on March 24, 1997 by the Encyclopedia Publishing Center, Inc. It is.

  The advantages of this tubular method are that it is relatively inexpensive and easy to operate, has a wide range of applicable resins, and is suitable for medium-scale production and multi-product production that is not suitable for mass production. By controlling the molding conditions, it is possible to obtain a balanced film in the longitudinal direction (MD direction) and lateral direction (TD direction) of the film, less ear loss compared to the T-die method, and the film temperature is glass. When the temperature is higher than the transition temperature, there is little chance of direct contact between the roll and clip equipment and the film, so there is no concern about sticking, etc. The bottom seal alone is very convenient and can be widened by opening one end, and the film width can be changed over a wide range by adjusting the amount of air blown. A.

  In the method for producing a polylactic acid-based resin film of the present invention, it is preferable to use a polylactic acid-based resin having a moisture content of 1200 ppm or less by drying the polylactic acid-based resin to be used at 60 to 110 ° C. for 6 hours or more. preferable. Furthermore, it is preferable to reduce the lactide content in the polylactic acid resin by vacuum drying the polylactic acid resin to be used under a high vacuum of a vacuum degree of 10 Torr or less. By reducing the water content in the polylactic acid resin to 1200 ppm or less and reducing the lactide content in the polylactic acid resin, hydrolysis during melt kneading can be prevented, thereby preventing a decrease in molecular weight, and strength and durability. Can be obtained.

  In the method for producing a polylactic acid-based resin film of the present invention, it is preferable to dry the plasticizer to be used at 60 to 110 ° C. for 6 hours or more so that the water content in the plasticizer is 4000 ppm or less. By reducing the amount of water in the plasticizer, hydrolysis during melt kneading can be prevented, thereby preventing a decrease in molecular weight, and a polylactic acid resin film excellent in strength and durability can be obtained.

  In the method for producing a polylactic acid-based resin laminated film of the present invention, it is preferable to form a film by a tubular method after extruding a polylactic acid-based resin and a plasticizer with a vent type twin screw extruder. When adding a plasticizer to a polylactic acid-based resin, it is preferable to use a twin screw extruder from the viewpoint of excellent kneadability. Further, a vent port is provided in the middle of the twin screw extruder, the vent port is depressurized, moisture and It is preferable to use a vent type twin screw extruder because it can melt and knead while removing low molecular weight components such as oligomers generated during melting. It is preferable to remove low molecular weight components such as oligomers under reduced pressure because a polylactic acid resin film excellent in strength and durability can be obtained.

  A polymer obtained by melting and kneading a polylactic acid resin and a plasticizer by extruding with a bent type twin screw extruder or the like is chipped, dried again to a moisture content of 1200 ppm or less, and then a single screw or twin screw extruder. However, in order to further reduce the lactide content by minimizing thermal degradation, a polylactic acid resin and a plasticizer can be vented in a twin screw extruder. After melt-kneading while reducing the pressure, it may be extruded as a tube as it is.

  In addition, when the melt-kneaded polymer is made into chips and dried and used again, it is desirable that the polymer chips be dried within at least 10 days after the melt-kneading to obtain polymer chips having a water content of 1200 ppm or less. If the melt-kneaded polymer chip is in a state where the moisture content is more than 1200 ppm for 11 days or more, the polymer is decomposed, and even after drying, it becomes difficult to form a polylactic acid resin film. The temperature of the extruder, polymer piping, die, etc. is preferably 200 ° C. or lower.

  In the manufacturing method of the polylactic acid-type resin film of this invention, it is more preferable that the cooling system of the first bubble is a water cooling system. By adopting a water cooling method as the cooling method, it is possible to rapidly cool the film, thereby lowering the crystallinity of the film and making it easy to reduce the haze value. There are advantages such as easier.

  In the method for producing a polylactic acid resin film of the present invention, the film temperature in the preheating step (preheating step in FIG. 1) is 5 to 15 ° C. lower than the glass transition temperature of the film (hereinafter referred to as Tg). It is preferable.

  When the film temperature in the preheating process is higher than (Tg-5 of the film) ° C., adhesion or the like is caused by the pinch roll before the preheating process, film formation becomes unstable, and a film with desired thickness unevenness and physical properties is obtained. I may not be able to. In addition, when the film temperature in the preheating step is lower than (Tg-15 of the film) ° C., film formation becomes unstable due to lack of heat at the time of stretching, and a film with desired thickness unevenness and flexibility is obtained. It may not be possible.

  In addition, the film temperature of this invention shall mean the temperature of the film measured by non-contact infrared rays etc.

  In the method for producing a polylactic acid resin film of the present invention, it is preferable to install an air ring as shown in FIG. 2 between the preheating step and the stretching step as shown in FIG. In the case where there is no air ring as shown in FIG. 2, the air in the stretching process becomes an ascending current and enters the preheating process, making it difficult to control the temperature of the preheating process, and the film temperature in the preheating process is 5 to 15 from the Tg of the film. It may be difficult to keep ℃ low. When the air ring is installed between the preheating step and the stretching step as shown in FIG. 1, it becomes possible to mix cold air in the rising airflow from the stretching step, and the film temperature in the preheating step is 5 to 15 ° C. lower than the Tg of the film. It becomes easy to maintain, and a film having desired thickness unevenness, heat resistance and flexibility can be easily obtained.

  In the manufacturing method of the polylactic acid-type resin film of this invention, the method of heating a film by using water as a medium in a preheating process is also preferable. More preferably, when the film is heated using water as a medium in the preheating step, the film is preheated with water having a temperature 5 to 15 ° C. lower than the Tg of the film. By heating the film using water as a medium, it becomes possible to heat the film in the preheating step without being affected by the heating in the stretching step, and the film temperature in the preheating step is 5 to 15 ° C. from the Tg of the film. It becomes easy to keep low, and a film with desired thickness unevenness, heat resistance and flexibility can be obtained.

  In the manufacturing method of the polylactic acid-type resin laminated film of this invention, it is preferable that the film temperature in an extending process is 0-20 degreeC higher than Tg of a film, More preferably, it is 0-15 degreeC from Tg of a film. This is the case for high temperatures.

  By stretching the film temperature in the stretching process at a temperature 0 to 20 ° C. higher than the Tg of the film, the polylactic acid resin as the base material is oriented and crystallized, and at the same time, the polylactic acid segment of the plasticizer is the polylactic acid type. Incorporation into the resin crystals is promoted, and volatilization, leaching and extraction of the plasticizer can be further suppressed. In addition, crystallization can be promoted while maintaining transparency, and strength physical properties are improved by orientation crystallization, so that a film having both flexibility and strength can be obtained. Furthermore, when the film temperature in the stretching step is 0 to 20 ° C. higher than the Tg of the film, the bubbles are stabilized and the film can be formed without tearing loss.

  If the temperature of the film in the stretching process is lower than the Tg of the film, it may be difficult to stretch, film formation may become unstable, and it may be difficult to obtain a film with desired thickness unevenness and flexibility. is there. When the temperature of the film in the stretching step is higher than (Tg-20 of the film) ° C., the bubble of the film becomes unstable, the film forming property is deteriorated, and a desired heat resistant film cannot be obtained. Sometimes.

  The draw ratio can be arbitrarily set in the range of 1.1 to 10 times in the longitudinal direction and the width direction, respectively, and either the longitudinal direction or the width direction may be increased or the same. The draw ratio of the film may be adjusted as appropriate according to the intended flexibility, handleability, and productivity. From the viewpoint of transparency, the polylactic acid segment of the plasticizer is promoted to be incorporated into the crystal. More preferably, it is 2 to 8 times, more preferably 2.5 to 8 times in at least one direction. Although it is not particularly limited, when a biaxially stretched film is used, if the stretching ratio in one direction exceeds 10 times, the stretchability deteriorates, and the film tends to break during film formation. Deterioration of transparency may occur.

  The area magnification which is the area ratio of the film before and after stretching is preferably 4 to 60 times, more preferably 6 to 40 times, and further preferably 6 to 30 times. From the viewpoint of productivity, a higher draw ratio is preferable.

  The heat treatment conditions are preferably performed at a higher temperature in the range from Tg to the melting point of the polylactic acid resin from the viewpoint of film strength and dimensional stability. In addition, for the purpose of reducing low molecular weight components such as oligomer components in the film, it is more preferable to perform heat treatment at 100 ° C. or higher for 10 seconds or longer.

Further, 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 method include corona discharge treatment, plasma treatment, flame treatment, acid treatment, and any method can be used, but continuous treatment is possible, and the apparatus is installed in an existing film forming facility. The corona discharge treatment can be exemplified as the most preferable because of its easy point and the simplicity of the treatment.
The polylactic acid-based resin film of the present invention is a film in which plasticizer volatilization, leaching, extraction (bleed out), and odor during heating use are sufficiently suppressed. When the polylactic acid-based resin laminated film of the present invention is used as, for example, a packaging wrap film, it has practically sufficient flexibility, transparency and strength properties immediately after the start of use, and in use, an oligomer or a plasticizer Since there is virtually no volatilization, leaching, or extraction (bleed out), flexibility and transparency can maintain the performance at the beginning of use for a long period of use, and it also has a strong odor even during heating use There is no problem that occurs. When a plasticizer having biodegradability is contained as a plasticizer, a packaging wrap film which can be composted as it is without being separated together with contents such as food after use can be obtained. Furthermore, since it is rich in stability over time, it does not deteriorate even after a long time after production, and a film that exhibits the original performance can be obtained.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, it is not limited by a following example.
[Measurement and evaluation method of characteristics]
(1) Identification of constituent components of film ¹ H-NMR (nuclear magnetic resonance apparatus) measurement and ¹³ C-NMR measurement of a film sample were performed to identify constituent components. If necessary, the film was hydrolyzed, the derivatization of the decomposition product, and the GC / MS measurement of the derivative product were performed, and the resin and the additive constituted were specified.

(2) Number average molecular weight of film components The sample was dissolved in a THF solution so as to be 1 mg / cc and measured in terms of polystyrene using GPC. The equipment is Shimadzu LC-10A series, the solvent is THF (for high performance liquid chromatography), the detector is RI detector (RID-10A), the column is Shodex (trademark) KF-806L and KF- 804L (each 300 mm × 8 mmφ) was used in series. The column temperature is 30 ° C., and the flow rate is 1.0 ml / min (on-line deaeration system with He). The polystyrene used for the standard is a polystyrene standard manufactured by Shodex (trademark). No. Used S-6850, S-1190, S-205, S-52.4, S-13.9, and S-1.31. These were measured by drawing a calibration curve with a cubic equation.
(3) Number average molecular weight of polylactic acid segment of plasticizer used in film After dissolving the film sample in chloroform, it was dropped into water and the precipitate was removed by filtration. The separated plasticizer was obtained by volatilizing the solvent of the filtrate from which the precipitate was removed. The number average molecular weight (hereinafter referred to as M) of the plasticizer was measured by the method described in (2). The separated plasticizer also performs ¹ H-NMR measurement, based on the chart obtained by the measurement,
M × (1/2) × 72 × I _PLA / ((1/2) × 72 × I _PLA + (1/4) × 44 × I _PEG )
The number average molecular weight of the polylactic acid segment in the plasticizer was calculated by the following formula. However, I _PEG is the signal integral intensity derived from the hydrogen of the methylene group of the PEG main chain, I _PLA is the signal integral intensity derived from the hydrogen of the methine group of the PLA main chain, and M (plasticizer) is the plasticizer The number average molecular weight of
(4) Glass transition temperature of the film [° C]
In accordance with JIS-K7121, by using a differential scanning calorimeter (DSC) manufactured by Seiko Instruments Inc., the temperature is increased from 0 ° C. to 200 ° C. at 10 ° C./min at a nitrogen gas flow rate of 25 ml / min. The glass transition temperature of the film was measured.

(5) Film flexibility: film tensile modulus [GPa]
A film sample was cut into a longitudinal direction of 150 mm and a width direction of 10 mm, and conditioned for 24 hours in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH in advance. This sample was subjected to a tensile test under the conditions of an initial length of 50 mm and a tensile speed of 300 mm / min using a Tensilon universal testing machine UTC-100 (manufactured by Orientec Co., Ltd.) in an atmosphere of 23 ° C. according to JIS K7161 and JIS K7127. The tensile modulus was measured. The measurement was performed 5 times in total, and the average value was obtained and used as the tensile modulus, and evaluated according to the following criteria.

  (Double-circle): The range whose tensile elastic modulus is 0.1 or more and less than 1.0 GPa.

  A: Tensile elastic modulus is in the range of 1.0 or more and less than 1.5 GPa.

  (Triangle | delta): The range whose tensile elasticity modulus is 1.5 or more and less than 2.0 GPa.

X: Tensile elastic modulus is less than 0.1 or 2.0 or more.
(6) Bleed-out resistance of film: mass change rate after hot water treatment [%]
For the film sample conditioned for 1 day or more in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH, the mass before the treatment is measured, treated in distilled water at 90 ° C. for 30 minutes, and again under the same conditions as before the treatment. After adjusting the humidity, the mass was measured. The mass change rate was calculated as the ratio of the mass change (decrease) before and after the treatment to the mass before the treatment, and was evaluated according to the following criteria.

  A: Mass change rate is less than 2%.

  A: Mass change rate is in the range of 2% or more and less than 5%.

  Δ: Mass change rate is in the range of 5% or more and less than 7%.

X: Mass change rate is 7% or more.
(7) Heat resistance: Heat resistance temperature [° C]
A double-sided tape is applied to an aluminum frame with a frame size of 150 mm square, and then a film sample is applied in a tensioned state so as not to be wrinkled, so that a double clip for stationery does not have a gap along the frame. The film was fixed on a frame, left in a hot-air oven maintained at a constant temperature for 5 minutes, and then removed to observe the state of the film.

  The test was repeated with the set temperature of the hot air oven (TABAI Labostar CONVENTION OVEN LC-112) changed in increments of 5 ° C., and the highest change was not observed, such as holes in the film or film fusing to the frame The temperature was a heat resistant temperature indicating heat resistance.

  A: Heat-resistant temperature is 150 ° C. or higher.

  ○: The heat resistant temperature is in the range of 130 ° C or higher and lower than 150 ° C.

(Triangle | delta): The range whose heat-resistant temperature is 120 degreeC or more and less than 130 degreeC.
X: Heat-resistant temperature is less than 100 degreeC.
(8) Uneven thickness [μm]
The film sample cut | disconnected in the width direction was created so that the length of a longitudinal direction might be 40 mm, and the thickness of the film sample in the width direction was measured by FILM THICKNESS TESTER made from Anritsu. The difference between the maximum value and the minimum value of the measured thickness was calculated and evaluated according to the following criteria.

  A: The difference between the maximum value and the minimum value of the thickness is less than 1 μm.

  ○: The difference between the maximum value and the minimum value of the thickness is 1 μm or more and less than 2 μm.

  Δ: The difference between the maximum value and the minimum value of the thickness is 2 μm or more and less than 4 μm.

X: The difference between the maximum value and the minimum value of the thickness is 4 μm or more. (9) Evaluation of film forming property Film forming is performed for 24 hours and evaluated. Although the film could be formed, those with tears were evaluated by dividing the number of tears by 24.
(10) Comprehensive evaluation Regardless of film forming property, if flexibility is ×, bleed-out resistance is ×, heat resistance is ×, or thickness unevenness is ×, overall evaluation is × Was also evaluated as a comprehensive evaluation x. In other cases, the overall evaluation was evaluated as ○.

[Polylactic acid resin used]
(Polylactic acid P1)
D body content = 12.0%
Water content = 490 ppm, melting point = none, weight average molecular weight = 200,000
(Polylactic acid P2)
D body content = 1.4%
Water content = 360 ppm, melting point = 166 ° C., weight average molecular weight = 220,000
The weight average molecular weight was measured by using Waters 2690 manufactured by Japan Waters Co., Ltd., using polymethyl methacrylate as a standard, a column temperature of 40 ° C., and a chloroform solvent.

[Method for producing plasticizer]
(Plasticizer S1)
By mixing 62 parts by mass of polyethylene glycol having a number average molecular weight of 8000, 38 parts by mass of L-lactide and 0.025 parts by mass of tin octylate and polymerizing at 150 ° C. for 3 hours in a nitrogen atmosphere, there are several at both ends of the polyethylene glycol. A plasticizer S1 having a polylactic acid segment having an average molecular weight of 2500 was obtained. When the water content was measured, it was 1650 ppm.
(Plasticizer S2)
80 parts by mass of polyethylene glycol having a number average molecular weight of 8000, 20 parts by mass of L-lactide and 0.025 parts by mass of tin octylate are mixed and polymerized at 150 ° C. for 3 hours in a nitrogen atmosphere, so that there are several at both ends of polyethylene glycol. A plasticizer S2 having a polylactic acid segment having an average molecular weight of 1000 was obtained. The water content was measured and found to be 1550 ppm.
(Plasticizer S3)
By mixing 20 parts by mass of polyethylene glycol having a number average molecular weight of 8000, 80 parts by mass of L-lactide and 0.025 parts by mass of tin octylate and polymerizing at 150 ° C. for 3 hours in a nitrogen atmosphere, there are several at both ends of polyethylene glycol. A plasticizer S3 having a polylactic acid segment having an average molecular weight of 12,000 was obtained. When the water content was measured, it was 1450 ppm.
[Film production method]
(Example 1)
A mixture of 55% by mass of polylactic acid P1, 16% by mass of polylactic acid P2 and 29% by mass of plasticizer S1 is melt-kneaded while being deaerated by using a vented twin-screw extruder with a cylinder temperature of 190 ° C. and a screw diameter of 44 mm. And then homogenized to obtain a chipped composition.

  This composition was dried with dehumidified hot air at a temperature of 100 ° C. and a dew point of −25 ° C. for 10 hours, and then supplied to a single screw extruder with a screw cylinder diameter of 190 ° C. and a screw diameter of 30 mm, a die diameter of 120 mm, and a lip clearance of 0.8 mm. The tube is extruded downward from a cylindrical die to form a first bubble, and the film is brought into contact with the inner surface of a sizing ring that has been passed through and overflowed with water at 19 ° C., cooled, taken up with a pinch roll, and a flat folded width A 215 mm tube-shaped unstretched film original fabric was formed.

  This tube-shaped unstretched film raw material is passed through two pinch rolls, a circumferential speed difference is made between them, and further through a preheating step in which the film is preheated with a ceramic heater. Air is injected into the air, and the amount of air and the peripheral speed difference between the rolls are adjusted, so that the second bubble is passed through a stretching process in which biaxial stretching is performed 3.0 times in the longitudinal direction and 2.8 times in the width direction. Then, 20 ° C. cooling air was blown on the air ring to solidify it, and a tubular flat stretched film was obtained. At that time, an air ring was installed between the preheating step and the stretching step, and cooling air at 20 ° C. was blown.

  Furthermore, the one side end surface of the tube-shaped flat stretched film was slit and developed to form a single stretched film that was not tubular.

The flat stretched film was heat-treated with a heating roll at 100 ° C. while holding the end with a belt to obtain a film having a final thickness of 10 μm. The film formation was stable for 24 hours without breaking. The evaluation results of the obtained film are shown in Table 1.
(Example 2)
A film was prepared in the same manner as in Example 1 except that a mixture of 20% by mass of polylactic acid P1, 35% by mass of polylactic acid P2, and 45% by mass of plasticizer S1 was used. The evaluation results of the obtained film are shown in Table 1.
(Example 3)
A film was prepared in the same manner as in Example 1 except that a mixture of 70% by mass of polylactic acid P1, 20% by mass of polylactic acid P2, and 10% by mass of plasticizer S1 was used. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 1)
A film was prepared in the same manner as in Example 1 except that a mixture of 75% by mass of polylactic acid P1, 22% by mass of polylactic acid P2, and 3% by mass of plasticizer S1 was used. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 2)
A film was prepared in the same manner as in Example 1 except that a mixture of 35% by mass of polylactic acid P1, 10% by mass of polylactic acid P2, and 55% by mass of plasticizer S1 was used. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 3)
A film was prepared in the same manner as in Example 1 except that a mixture of 55% by mass of polylactic acid P1, 16% by mass of polylactic acid P2, and 29% by mass of plasticizer S2 was used. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 4)
A film was prepared in the same manner as in Example 1 except that a mixture of 55% by mass of polylactic acid P1, 16% by mass of polylactic acid P2, and 29% by mass of plasticizer S3 was used. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 5)
While trying to form a film in the same manner as in Example 1 except that no air ring was installed between the preheating step and the stretching step, the bag-like film could not be opened during the preheating and stretching steps, A film could not be formed.
(Comparative Example 6)
A film was prepared in the same manner as in Example 1 except that the film temperature in the stretching step was 86 ° C. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 7)
A film was prepared in the same manner as in Example 1 except that the film temperature in the preheating step was 10 ° C and the film temperature in the stretching step was 25 ° C. The evaluation results of the obtained film are shown in Table 1.
Example 4
A film was prepared in the same manner as in Example 1 except that the medium for the preheating step was water at 25 ° C. The evaluation results of the obtained film are shown in Table 1.

The symbols in Table 1 have the following meanings.
P1: Polylactic acid P1
P2: Polylactic acid P2
S1: Plasticizer S1
S2: Plasticizer S2
S3: Plasticizer S3

  By adopting the production method of the present invention, not only wrapping films for packaging, but also other packaging materials, films for agriculture, films for industrial materials such as automobile film protective sheets, garbage bags, compost bags, and various soft vinyl chlorides can be obtained. A polylactic acid resin film useful as a film for industrial materials to be used can be stably produced, but its application range is not limited thereto.

The figure which shows the preheating process and the drawing process in the tubular method Cross section of air ring

Explanation of symbols

1 Preheating process 2 Air ring 3 Stretching process 4 Cooling air 5 Rectification chamber

Claims (4)

  A polylactic acid resin film comprising 50 to 95% by weight of a polylactic acid resin and 5 to 50% by weight of a plasticizer with respect to a total of 100% by weight of the polylactic acid resin and the plasticizer, wherein the plasticizer is a single molecule. A plasticizer having at least one polylactic acid segment having a molecular weight of 1,200 or more and 10,000 or less and having a polyether segment and / or a polyester segment, After forming the first bubble with the molten resin discharged from the resin in a tube shape, cooling and taking the tube-shaped resin into a flat shape, the film undergoes a preheating step and a stretching step to form a second bubble, After that, it is cooled, and the tubular film is flattened and taken up, and then wound up. Film temperature of 5 to 15 ° C. lower and stretching process than the glass transition temperature is equal to or 0 to 20 ° C. higher than the glass transition temperature of the film, the production method of polylactic acid-based resin film.   The method for producing a polylactic acid-based resin film according to claim 1, wherein an air ring is provided between the preheating step and the stretching step.   The method for producing a polylactic acid resin film according to claim 1, wherein a preheating step is performed using water as a medium.   The method for producing a polylactic acid-based resin film according to claim 3, wherein preheating is performed with water having a temperature 5 to 15 ° C lower than the glass transition temperature in the preheating step.

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