JP2008120865A - Manufacturing method of polylactic acid resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably manufacture a polylactic acid resin film that exhibits sufficient flexibility and is suppressed in volatilization, exudation and extraction (bleeding out) of a plasticizer and the like. <P>SOLUTION: The polylactic acid resin film comprising 50-95 mass% of the polylactic acid resin and 5-50 mass% of a plasticizer is manufactured by an inflation method or a tubular method, where the plasticizer has at least one polylactic acid segment having a molecular weight of at least 1,200 and less than 10,000 in one molecule and a polyether-based segment and/or a polyester-based segment, and the polylactic acid resin film has an MVR value at 170°C of at most 25 cm<SP>3</SP>/10 min. <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, particularly a film useful as a wrapping film for food packaging.

  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 technique relating to 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 provided with flexibility by adding a plasticizer. Is 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. However, since it contains a liquid plasticizer at room temperature, the mechanical properties of the present inventors are The target level was not reached. Moreover, although the manufacture is formed into a film by uniaxial stretching and biaxial stretching, it does not give any suggestion to the film forming technology of the tube-like seamless packaging film.

  On the other hand, Patent Document 4 describes a technique related to a biodegradable tubular method. This document relates to starch-based foamed sheets and products. As a production method, a method of extruding through a tube head is described, but it is a technique for a special foam sheet having a cell distribution.

  The technique of Patent Document 5 is the first to use a biodegradable heat-shrinkable film by a tubular method using a polylactic acid resin. In this technique, a film having a specific composition comprising a polylactic acid resin (A) and a biodegradable aliphatic polyester (B) having a glass transition temperature Tg of 0 ° C. or less is formed by a tubular stretching method, and shrink wrapping is performed. The body was made. As film forming conditions, the glass transition temperature of the polylactic acid-based resin, the MD direction speed ratio when forming the bubble, and the like are controlled. The resulting film had good heat shrinkability and easy cutability, but the transparency was not at the level we aimed for. The reason for this is considered to be a microphase-separated structure due to the mixing of polymers having different structures.

As described above, although various studies have been made in the past, the actual situation is that the target level of the present inventors has not been reached.
JP 7-257660 A JP 2000-26623 A JP 2004-143432 A Special table 2003-523432 gazette Japanese Patent Laid-Open No. 2003-181919

  The problem to be solved by the present invention relates to a method for producing a film by an inflation method or a tubular method, which is suitable for obtaining a polylactic acid resin film having excellent adhesion in addition to flexibility, transparency and heat resistance. Is.

The present invention adopts the following means in view of the above-described state of the prior art. That is, when 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 is formed, the plasticizer has a molecular weight of 1,200 to 10,000 in one molecule. has less than polylactic acid segment one or more of a plasticizer having a polyether-based segments and / or polyester segment, and, MVR values at 170 ° C. of the polylactic acid resin film is 25 cm ³ / 10min or less of A method for producing a polylactic acid-based resin film, characterized by forming a film by an inflation method or a tubular method, which is a range.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method which can obtain the polylactic acid-type resin film which has the property excellent in adhesiveness in addition to a softness | flexibility, transparency, and heat resistance, and can produce many kinds and small quantities is provided. The

  The film can be suitably used for various applications by taking advantage of its features, but can be particularly suitably used as a wrapping film for food packaging.

  The present invention has intensively studied a polylactic acid resin film having flexibility, transparency, and heat resistance required for a wrap film, a stretch film, etc., and specified a polylactic acid resin having a specific composition and a specific plasticizer. It was found that the target can be satisfied by forming the film by this method.

  That is, in order to impart flexibility and transparency to the polylactic acid resin film, 50 to 95 mass% of the polylactic acid resin and 5 to 50 mass% of the specific plasticizer are used. The MVR value at ° C. is produced by the inflation method or the tubular method within the optimum range.

  Next, the polylactic acid resin film of the present invention and the production method thereof will be further described. 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 a polymer of 70% by mass or more. And / or homopolylactic acid composed of 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. When the polylactic acid resin used in the present invention does not have crystallinity, the volatilization, leaching, and extraction (bleed out) of the plasticizer cannot 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. When the weight average molecular weight is at least 50,000, strength properties are excellent when a molded article such as a film is formed.

  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 at least one polylactic acid segment having a molecular weight of 1,200 or more and less than 10,000 in one molecule and having a polyether-based and / or polyester-based segment. Is preferred. 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 molecular weight of the polylactic acid segment in one molecule of the plasticizer is 1,200 or more and less than 10,000, so that a large amount of the polylactic acid segment is taken into the crystal of the base material in terms of plasticization efficiency. It is preferable from the viewpoint of suppressing volatilization, exudation, and extraction (bleed out). 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 polylactic acid resin film of the present invention preferably comprises 50 to 95% by mass of a polylactic acid resin and 5 to 50% by mass of a plasticizer. 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 70 to 85% by mass and the plasticizer is 15 to 30% by mass, It is good from the viewpoint of handleability and barrier properties when used. If the polylactic acid resin is less than 50% by mass, polylactic acid is present in the plasticizer, making it very difficult to add the plasticizer to the polylactic acid resin, and forming a film 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, problems such as inability to peel off due to sticking to articles to be packaged may occur, or gas barrier properties may be inferior. In addition, when the content of the polylactic acid resin exceeds 95% by mass, the flexibility is inferior, the shape does not change 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.

  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.

Furthermore, the molecular weight of the polyether-based and / or polyester-based segment in one molecule of the plasticizer of the present invention is preferably 7000 or more and less than 20000. By making the molecular weight of the polyether-based and / or polyester-based segment in one molecule of the plasticizer 7000 or more and less than 20000, the polylactic acid-based resin film has desired flexibility, and the polylactic acid-based resin film preferred also the MVR value at 170 ° C. from the viewpoint that it is possible to stabilize the film as follows 25 cm ³ / 10min.

  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.

  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. Further, from the viewpoint of improving transparency, particles having a refractive index close to that of the polylactic acid resin used as the substrate are preferable, and particles such as silica, colloidal silica, and polymethyl methacrylate are more preferable in this respect. Further, as the particles used for the polylactic acid resin 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 molecular weight of 1,200 or more and less than 10,000 in one molecule, and is polyether-based and / or polyester-based. When a component other than a plasticizer having a segment is contained, it is preferable to select a component having biodegradability.

  For example, the plasticizer used in the present invention is prepared by polymerizing a polylactic acid oligomer having a molecular weight of 1,200 or more and less than 10,000 in advance by a conventional method such as a lactide ring-opening method or a lactic acid condensation polymerization method. A polyether-based and / or polyester-based segment which is obtained by reacting a suitable amount with a compound having a polyether-based and / or polyester-based segment which is a main component of a plasticizer. Is added to this by ring-opening polymerization of lactide as a polymerization initiator, or by dehydration condensation polymerization of lactic acid using a compound having a polyether-based and / or polyester-based segment as a main component of a plasticizer as a polymerization initiator. You may add to this. In addition, a bifunctional compound such as a dicarboxylic acid anhydride compound or a diisocyanate compound is obtained by treatment such as heating and kneading in the presence of a polylactic acid oligomer having a molecular weight of 1,200 or more and less than 10,000 and a compound comprising the main component of the plasticizer. The chemical 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 molecular weight of 1,200 or more and less than 10,000 in one molecule and having a polyether-based and / or polyester-based segment will be described. .

  A polyethylene glycol having a hydroxyl terminal at both ends (hereinafter referred to as PEG) is prepared. The number average molecular weight (MPEG) of a PEG having hydroxyl groups at both ends 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 wA parts by mass are added to PEGwB parts by mass of PEGwB having both ends at the ends, lactide undergoes ring-opening addition polymerization at both ends of hydroxyl groups of PEG and sufficiently reacted, so that PLA (A)- A block copolymer of the PEG (B) -PLA (A) 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 the plasticizer made of this block copolymer can be determined substantially as (1/2) × (wA / wB) × MPEG. Moreover, the mass ratio with respect to the whole plasticizer of a polylactic acid segment component can be calculated | required substantially as 100xwA / (wA + wB)%. Furthermore, the mass ratio of the plasticizer component excluding the polylactic acid segment component to the entire plasticizer can be substantially calculated as 100 × wB / (wA + wB)%.

When the plasticizer contains a large amount of unreacted PEG, a reaction product with PEG having a molecular weight of less than 1,200 at the terminal polylactic acid segment, a by-product such as a lactide oligomer, or a large amount of impurities, for example, These are preferably removed 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 the by-products and the like, such as lactide oligomers, polylactic acid resin can be prevented from being low viscosity, the MVR value at 170 ° C. of the polylactic acid-based resin film to a 25 cm ³ / 10min or less Also preferred.

When a plasticizer of a PLA (A) -PEG (B) -PLA (A) type block copolymer is prepared by the method described above, the molecular weight of one polylactic acid segment of the prepared plasticizer is as follows: It can be determined by the method. That is, based on a chart obtained by ¹ H-NMR measurement using a deuterated chloroform solution of a plasticizer, {IPLA × (molecular weight of polylactic acid monomer unit) / (number of polylactic acid segments)} / {IPEG × (Molecular weight of PEG monomer unit) / (number of chemically equivalent protons)} × MPEG. That is, when a plasticizer of a PLA (A) -PEG (B) -PLA (A) type block copolymer is prepared, {IPLA × 72/2} / {IPEG × 44/4} × MPEG. . However, IPEG is the signal integral intensity derived from hydrogen of the methylene group of the PEG main chain part, and IPLA is the signal integral intensity derived from hydrogen of the methine group of the PLA main chain part. When synthesizing under the conditions that the reaction rate of lactide during plasticizer synthesis is sufficiently high and almost all lactide is ring-opening-added to the PEG end, the chart obtained by ¹ H-NMR measurement is often used. It is preferable to obtain the molecular weight of one polylactic acid segment of the plasticizer by the above method.

  As a method for separating the used plasticizer from the polylactic acid resin film in the present invention for the evaluation of the molecular weight of the polylactic acid segment in the plasticizer, for example, the polyester is uniformly mixed in an appropriate good solvent such as chloroform. After being dissolved, the solution is dropped into a suitable poor solvent such as water or water / methanol mixed solution, and the precipitate mainly containing polylactic acid resin is removed by filtration, and the separated plasticizer is evaporated by evaporating the solvent of the filtrate. Examples thereof include, but are not limited to, a reprecipitation method to be obtained, 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 M) using GPC (gel permeation chromatography) or the like. And a polylactic acid segment, a polyether-based segment and / or a polyester-based segment are identified by ¹ H-NMR measurement or the like. By using these measurement results, the molecular weight of one polylactic acid segment possessed by the plasticizer separated from the polylactic acid 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 × (molecular weight of PLA monomer unit = 72)}]. However, I _PEPE is the signal integral 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 in the polyether-based segment and / or polyester-based segment that gives the signal integral intensity.

  For example, a PLA (A) -PEG (B) -PLA (A) type block copolymer having one or more polylactic acid segments having a molecular weight of 1,200 or more and less than 10,000 in one molecule obtained by the above-described method. Provided is a polylactic acid resin film that has sufficient flexibility and suppresses volatilization, exudation, and extraction (bleed out) of a plasticizer, which cannot be achieved by the prior art by using a polymer as a plasticizer. In particular, a sufficient effect can be obtained.

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 MVR value of the polylactic acid resin film at 170 ° C. is set. preferable in order to 25 cm ³ / 10min or less. 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 polylactic acid-based resin film of the present invention is representative of bags, etc. as necessary, as long as it does not impair the effects of the present invention, such as heat sealability, gas barrier properties such as water vapor, oxygen, carbon dioxide, release properties, printability, etc. Properties required as packaging materials for goods and foods to be used may be imparted. As such a method, a polymer or a compound having the functions as described above is blended in a film, and at least one surface of the film is thermosetting, such as acrylic resin, polyester resin or silicone resin, thermoplastic resin or charging. A method of applying an inhibitor, a surfactant, a release agent, etc. to the surface, a method of co-extruding other films with the above functions such as polyolefin sealants in the extrusion process, and laminating by bonding such as adhesion and lamination In view of the purpose of the present invention, it is preferable to use a biodegradable resin or composition.

  Next, the manufacturing method of the present invention will be described. The method for producing the polylactic acid resin film in the present invention is an inflation method or a tubular method. The film production method by the inflation method is, for example, a method described on pages 199 to 202 of “Practical Plastic Molding Encyclopedia” issued on March 24, 1997 by the Encyclopedia of Industrial Research Co., Ltd. is there.

  Specifically, the raw material resin is supplied to a single-screw or twin-screw extruder, melted and mixed, and directly inflated into a bubble shape by the air filled with the molten resin extruded into a tube shape from a cylindrical die, and air-cooled or water-cooled. It is a method of picking up with a pinch roll.

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

  Specifically, the first bubble is formed with molten resin that is melt-mixed and extruded as it is into a tube shape from a cylindrical die, the resin is quenched with water or air cooling, pinched with a pinch roll, and the tube-shaped resin is flattened. After that, the resin is heated again to a temperature not lower than the glass transition temperature (Tg) and not higher than the melting point (Tm) by a method such as infrared heater heating or hot air heating, and then a gas such as air or a liquid such as water is used. Then, the MD and TD directions are stretched simultaneously by forming a second bubble, then cooled to a temperature of Tg or lower, pinched with a pinch roll, and taken up into a flat shape, and then wound up. To obtain a biaxially stretched film.

  The merit of this inflation method or tubular method is that the equipment cost is relatively low and operation is easy, the range of applicable resins is wide, medium-scale production that is not suitable for mass production, and multi-product production That the film is balanced in the longitudinal direction (MD direction) and lateral direction (TD direction) by controlling the molding conditions, the ear loss is less than the T-die method, and the film When the temperature is Tg or higher, there is little chance of direct contact between the roll and clip devices and the film, so there is no concern about sticking, etc. It can be obtained by using only the bottom seal, and it can be widened by opening one end, and the film width can be widened by adjusting the air blowing amount. Erareru it, and the like.

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 with a degree of vacuum of 10 Torr or less. By reducing the water content in the polylactic acid resin to 1200 ppm or less and the lactide content in the polylactic acid resin, hydrolysis during melt-kneading can be prevented, thereby preventing a decrease in molecular weight. the MVR value at 170 ° C. of the film can be less 25 cm ³ / 10min, also it is possible to obtain strength, excellent polylactic acid resin film durability.

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 a plasticizer to prevent hydrolysis during melt-kneading, whereby it is possible to prevent a decrease in molecular weight, the MVR value at 170 ° C. of the polylactic acid-based resin film or less 25 cm ³ / 10min In addition, a polylactic acid resin film excellent in strength and durability can be obtained.

In the method for producing a polylactic acid resin film of the present invention, it is preferable to form a film by an inflation method or a tubular method after extruding a polylactic acid 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 bent twin-screw extruder because it can melt and knead while removing low molecular weight components such as oligomers generated during melting. To remove low molecular weight components such as oligomers by vacuum is preferably a MVR value at 170 ° C. of the polylactic acid-based resin film to be a less 25 cm ³ / 10min.

  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. Melt-kneading the polymer chips, the elapsed amount of water 1200ppm more remains 11 days or more will be decomposed polymer be then dried, MVR values at 170 ° C. of the polylactic acid-based resin film is 25 cm ³ / 10min or less The polylactic acid resin film cannot be obtained. The temperature of the extruder, polymer piping, die, etc. is preferably 200 ° C. or lower.

In the polylactic acid-based resin film manufacturing method of the present invention, (measured according to JIS-K7210) MVR values at 170 ° C. of the polylactic acid-based resin film 0 m ³ / 10min or more 25 cm ³ / 10min must be less that There is preferably not more than 0 m ³ / 10min or more 18cm ³ / 10min. When MVR value exceeds 25 cm ³ / 10min, the film is too soft, bubble sensitive to air amount increase or decrease, or become unstable film, when the inflation method of the top-blown, will dripping polymer , Film formation is impossible. The MVR value at 170 ° C. of the polylactic acid-based resin film is preferably as low a degree as possible the extrusion is considered to 0.1 m ³ / 10min about the lower limit according to the state of the art.

  In the method for producing a polylactic acid resin film of the present invention, it is preferable to use an inflation method in which the film cooling method is a water cooling method or a tubular method in which the film cooling method is a water cooling method. In the tubular method, the cooling method of the first bubble is more preferably a water cooling method. By adopting a water-cooling method as the cooling method, it is possible to rapidly cool the film, whereby the crystallinity of the film can be lowered and the haze value can be easily lowered. In the tubular method, the cooling method of the first bubble is the water cooling method, so that the film can be rapidly cooled, thereby reducing the crystallinity of the film and easily extending the second bubble. There are advantages such as becoming.

  In the method for producing a polylactic acid-based resin film of the present invention, when the film cooling method uses a water-cooled inflation method or the film cooling method uses a water-cooled tubular method, the glass transition temperature of the polylactic acid-based resin film ( It is preferable to cool with cooling water having a temperature 5 to 20 ° C. lower than Tg). When the cooling water temperature is higher than (Tg-5) ° C., the first bubble is soft and sensitive to the increase / decrease of air and the flow of ambient air, and film formation may become unstable. On the other hand, when the cooling water temperature is lower than (Tg-20) ° C., it becomes a hard and brittle first bubble, the film loses flexibility, and the bubble cannot be held and may be broken.

  In the method for producing a polylactic acid-based resin film of the present invention, when the film is produced by a tubular method, the stretching conditions of the film are appropriately adjusted according to the desired heat shrinkage characteristics, dimensional stability, strength, elastic modulus, and the like. Can be done in any way. Stretching and crystallizing the base polylactic acid resin by stretching, and at the same time promoting the incorporation of the polylactic acid segment of the plasticizer into the crystal of the polylactic acid resin. Extraction 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.

  For example, the stretching temperature is preferably from the glass transition temperature to the crystallization temperature of the polylactic acid-based resin to be used from the viewpoint of biaxial stretching properties and film transparency.

  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 is preferably performed at a higher temperature in the range from the glass transition temperature 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.

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

  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 elastic modulus is larger than 1.5 GPa, the flexibility is lowered and the application field of the polylactic acid resin film is decreased, which is not preferable. When the tensile elastic modulus is smaller than 0.1 GPa, the release property of the wound film is inferior, and the process passability deteriorates 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, containers such as trays, seedling pots, flower pots and the like.

  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 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. 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 also generate a strong odor even during heating use There is no problem of doing. 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. Also, in various post-processing steps of molded products performed after film formation, etc., it is possible to obtain a film having stable flexibility and transparency even after various dry heat processing and after processing in a high temperature atmosphere. it can.

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 film constituents ¹ H-NMR (nuclear magnetic resonance apparatus) measurement and ¹³ C-NMR measurement of a film sample were performed to identify the constituents. If necessary, the film was hydrolyzed, the derivatization of the degradation product, and the GC / MS measurement of the derivative were performed, and the resin and additives that were 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 Showa Denko's Shodex (trademark) KF-806L and KF −804L (each 300 mm × 8 mmφ) was used in series. Column temperature is 30 ° C., flow rate is 1.0 ml / min (online degassing with He). The polystyrene used for the standard is a polystyrene standard manufactured by Shodex (trademark), and Std. 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 a film sample in chloroform, the precipitate was removed by dropping into water and filtering. The separated plasticizer was obtained by volatilizing the solvent of the filtrate from which the precipitate was removed. The plasticizer was measured for the number average molecular weight (hereinafter referred to as M) of the plasticizer by the method described in (2). The separated plasticizer was also subjected to ¹ H-NMR measurement, and 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. Where I _{PE G} is the signal integral intensity derived from hydrogen of the methylene group of the PEG main chain, I _PLA is the signal integral intensity derived from hydrogen of the methine group of the PLA main chain, and M (plasticizer) is plastic The number average molecular weight of the agent.

(4) Film, MVR value of polylactic acid resin [cm ³ / 10min]
After the sample was dried and the water content was reduced to 700 ppm or less, the MVR value of the film was measured with a melt indexer at a load of 2.16 kg and a temperature of 170 ° C. in accordance with the JIS-K7 120 B method. For samples that could not be formed, the sample was measured by sampling the discharged polymer.

(5) 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. For those incapable of forming a film, the discharge polymer was sampled and measured.

(6) 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 previously conditioned for 24 hours in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH. Using a Tensilon universal testing machine U TC-100 type (manufactured by Orientec Co., Ltd.) under an atmosphere of 23 ° C. in accordance with JIS K7161 and JIS K7127, the sample was tensioned at an initial length of 50 mm and a tension speed of 300 mm / min. A test was conducted to measure the tensile modulus. 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 2.0 or more.
(7) Bleed-out resistance of film: Mass change rate after hot water treatment [%]
Measure the pre-treatment mass of a film sample that has been conditioned for 1 day or more in an atmosphere of temperature 23 ° C and humidity 65% RH, treat it in distilled water at 90 ° C for 30 minutes, and then re-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.
(8) Moisture content measurement of each raw material [ppm]
Using a Karl Fischer moisture meter MKC-510N (Kyoto Electronics Co., Ltd.), the measurement was performed by the Karl Fischer method (coulometric titration method). The heating conditions during the measurement were 150 ° C.
(9) Evaluation of film forming property Film forming was 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 Comprehensive evaluation of flexibility, bleed-out resistance, and film-forming property. Comprehensive evaluation ◎, flexibility and bleed-out resistance are excellent. , Bleed-out resistance is △ or ○, and the film was formed without breakage for 24 hours. Overall evaluation ○, flexibility, bleed-out resistance was △, ○, or ◎, and breakage occurred in film formation for 24 hours. The overall evaluation Δ, regardless of the film-forming property, was evaluated as × if the flexibility or bleed-out resistance was ×, and × if the film could not be formed.
[Polylactic acid resin used]
(Polylactic acid P1)
Grade name "4060D" made by Nature Works
D-isomer content ^{= 12.0%, MVR = 3cm 3} / 10min
Water content = 490 ppm, Tm = none, weight average molecular weight = 200,000
(Polylactic acid P2)
Grade name "4032D" made by Nature Works
D-isomer content ^{= 1.4%, MVR = 2cm 3} / 10min
Water content = 360 ppm, Tm = 166 ° C., weight average molecular weight = 220,000
(Polylactic acid P3)
Grade name "6250D" made by Nature Works
D-isomer content ^{= 1.4%, MVR = 30cm 3} / 10min
Water content = 450 ppm, Tm = 166 ° C., weight average molecular weight = 110,000
(Polylactic acid P4)
Grade name "4042D" made by Nature Works
D-isomer content ^{= 4.0%, MVR = 2cm 3} / 10min
Water content = 380 ppm, Tm = 153 ° C., weight average molecular weight = 220,000
(Polylactic acid P5)
Grade name "4060D" made by Nature Works
D-isomer content ^{= 12.0%, MVR = 3cm 3} / 10min
Water content = 8090 ppm, Tm = none, weight average molecular weight = 200,000
[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)
By mixing 62 parts by mass of polyethylene glycol having a number average molecular weight of 10,000, 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 S2 having a polylactic acid segment with an average molecular weight of 2400 was obtained. The water content was measured and found to be 1380 ppm.
(Plasticizer S3)
By mixing 62 parts by mass of polyethylene glycol having a number average molecular weight of 6000, 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 S3 having a polylactic acid segment with an average molecular weight of 2300 was obtained. The water content was measured and found to be 1500 ppm.
(Plasticizer S4)
Polyethylene glycol having a number average molecular weight of 8,000. The water content was measured and found to be 1700 ppm.
(Plasticizer S5)
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. The water content was measured and found to be 9050 ppm.
[Additives used]
(Additive A1)
Carbodiimide-modified isocyanate (manufactured by Nisshinbo Co., Ltd., product name: Carbodilite LA-1)
[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 diameter of 30 mm at an extruder cylinder temperature of 190 ° C., a die diameter of 120 mm, and a lip clearance of 0.8 mm. The tube is extruded downward from a cylindrical die, and the film is brought into contact with the inner surface of the sizing ring that has been passed through and overflowed with water at 19 ° C., cooled, taken up with a pinch roll, and unfolded into a tube-like unstretched film with a folding width of 215 mm Formed. This tube-shaped unstretched film raw material is passed through two pinch rolls, a circumferential speed difference is made between them, and further, a ceramic heater is used to heat the film so that the film temperature is 40 to 45 ° C. Air was injected into the inside, and the amount of air and the peripheral speed difference between the rolls were adjusted, so that the film was simultaneously biaxially stretched 3.0 times in the longitudinal direction and 2.8 times in the width direction. Then, 20 degreeC cooling air was sprayed and solidified with the air ring, and the tubular stretched film was obtained. Furthermore, the one side end surface of the tubular stretched film was slit and developed to form a flat stretched film. 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 55% by mass of polylactic acid P1, 6% by mass of polylactic acid P2, 10% by mass of polylactic acid P3, and 29% by mass of plasticizer S1 was used. During film formation, tearing occurred once every 24 hours on average. 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 mixture of 35% by mass of polylactic acid P1, 10% by mass of polylactic acid P2, and 55% by mass of plasticizer S1 is melt-kneaded while being deaerated by using a vented twin-screw extruder with a cylinder diameter of 190 ° C. and a screw diameter of 44 mm. Attempts were made to melt-knead the polylactic acid resin and the plasticizer.
(Example 3)
A film was prepared in the same manner as in Example 1 except that the plasticizer S2 was used as the plasticizer. 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 the plasticizer S3 was used as the plasticizer, but no film could be formed. The MVR and glass transition temperature of the discharged polymer were measured, and the results 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 P3, and 29% by mass of plasticizer S1 was used. could not. The MVR and glass transition temperature of the discharged polymer were measured, and the results are shown in Table 1.
(Comparative Example 5)
A film was prepared in the same manner as in Example 1 except that the plasticizer S4 was used as the plasticizer. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 6)
A film was prepared in the same manner as in Example 1 except that a mixture of 55% by mass of polylactic acid P5, 16% by mass of polylactic acid P2, and 29% by mass of plasticizer S1 was used. could not. The MVR and glass transition temperature of the discharged polymer were measured, and the results are shown in Table 1.
(Comparative Example 7)
A film was prepared in the same manner as in Example 1 except that the plasticizer S5 was used as the plasticizer, but no film was formed. The MVR and glass transition temperature of the discharged polymer were measured, and the results are shown in Table 1.
Example 4
A film was prepared in the same manner as in Example 1 except that the cooling water temperature was 28 ° C. During film formation, tearing occurred once every two hours on average. The evaluation results of the obtained film are shown in Table 1.
(Example 5)
A mixture of 55% by mass of polylactic acid P1, 16% by mass of polylactic acid P2, and 29% by mass of plasticizer S1 was supplied to a vent type twin screw extruder having a screw diameter of 30 mm, and the same as in Example 1 while degassing The film was extruded from a cylindrical die, and a film was prepared in the same manner as in Example 1. The film formation was stable without breaking for 24 hours. The evaluation results of the obtained film are shown in Table 1.
(Example 6)
A film was prepared in the same manner as in Example 1 except that a mixture of 44% by mass of polylactic acid P1, 13% by mass of polylactic acid P2, 20% by mass of polylactic acid P4, and 23% by mass of plasticizer S1 was used. During film formation, tearing occurred once every 3 hours on average. The evaluation results of the obtained film are shown in Table 1.
(Example 7)
A film was prepared in the same manner as in Comparative Example 5 except that the cooling water temperature was 30 ° C. The film formation was stable without breaking for 24 hours. The evaluation results of the obtained film are shown in Table 1.
(Example 8)
A mixture of 44% by mass of polylactic acid P1, 13% by mass of polylactic acid P2, 20% by mass of polylactic acid P4 and 23% by mass of plasticizer S1 was fed into a vented twin screw extruder having a cylinder temperature of 190 ° C. and a screw diameter of 44 mm. Then, the mixture was melt-kneaded and homogenized while being deaerated to obtain a chipped composition. This composition was dried at 100 ° C. for 10 hours with dehumidified hot air, then supplied to a single screw extruder with a screw diameter of 45 mm, and from a cylindrical die with a die diameter of 100 mm and a lip clearance of 1.3 mm at an extruder cylinder temperature of 190 ° C. The tube was extruded upward, taken up with a pinch roll while being cooled by air with a cooling ring, and the tubular film was wound up with a winder. By adjusting the amount of air injected into the bubble and the take-up speed of the pinch roll, a film with a folding width of 300 mm and a final thickness of 30 μm was obtained. The film formation was stable without breaking for 24 hours. The evaluation results of the obtained film are shown in Table 1.
Example 9
Film as in Example 5 except that a mixture of 54.5% by mass of polylactic acid P1, 16% by mass of polylactic acid P2, 29% by mass of plasticizer S1, and 0.5% by mass of additive A1 is provided. It was created. The film formation was stable without breaking for 24 hours. The evaluation results of the obtained film are shown in Table 1.

The symbols in Table 1-1 and Table 1-2 have the following meanings.
P1: Polylactic acid P1
P2: Polylactic acid P2
P3: Polylactic acid P3
P4: Polylactic acid P4
P5: Polylactic acid P5
S1: Plasticizer S1
S2: Plasticizer S2
S3: Plasticizer S3
S4: Plasticizer S4
S5: Plasticizer S5
A1: Additive A1

  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.

Claims (4)

When forming 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, the plasticizer has a molecular weight of 1,200 or more and less than 10,000 in one molecule. having a polylactic acid segment more than one, a plasticizer having a polyether-based segments and / or polyester segment, and, in a range MVR value is below 25 cm ³ / 10min at 170 ° C. of the polylactic acid-based resin film A method for producing a polylactic acid-based resin film, characterized by forming a film by an inflation method or a tubular method.   The method for producing a polylactic acid-based resin film according to claim 1, wherein the film is formed by an inflation method or a tubular method after being extruded by a vent type twin screw extruder.   The manufacturing method of the polylactic acid-type resin film of Claim 1 or 2 which forms into a film by the inflation method or the tubular method whose cooling method after nozzle | mouth discharge is a water cooling system.   The method for producing a polylactic acid-based resin film according to claim 3, wherein cooling is performed with cooling water having a temperature 5 to 20 ° C lower than the glass transition temperature of the resin after discharging the die.