JP2008169238A - Polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film not only excellent in flexibility and close adhesion required for a wrap film, stretch film or bag body, but also excellent in water vapor barrier property, and also suppressed with the bleed out of plasticizer and change of film characteristics over time. <P>SOLUTION: This polyester film is provided by consisting of 50-95 mass% polylactic acid resin and 5 to 50 mass% plasticizer based on 100 mass% total of the polylactic acid resin and plasticizer. The plasticizer has (A) a polymer plasticizer having a polylactic acid segment and (B) a plasticizer having ≤30°C melting point, the amount of the (A) polymer plasticizer is larger than that of (B) the liquid plasticizer, and the tensile elastic modulus of the polyester film is 0.1 to 2 GPa. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a polyester film that can be suitably used as a packaging film for articles and foods such as wrap films, stretch films, bags, etc. excellent in balance of properties such as flexibility, adhesion, and barrier properties and suppression of bleeding out. It is about.

  Conventionally, as a method of disposing of a polymer resin molded product used for packaging materials or the like, a method of processing by a method such as incineration or landfill has been long. However, in recent years, waste disposal issues such as greenhouse gas emissions from incineration, deterioration of incinerators due to high combustion heat, environmental pollution due to landfill reduction and dumping have become a major issue. Under such circumstances, biodegradable plastics have attracted a great deal of attention as environmentally friendly materials that are degraded by enzymes and microorganisms. In particular, products related to molded articles using aliphatic polyesters, particularly polylactic acid, have been actively developed. In particular, a polyester film made of a polylactic acid resin has been developed in the industrial materials and packaging materials fields.

  Polylactic acid is a polymer obtained by producing lactic acid using starch obtained from cereals such as corn, and potatoes such as sweet potato, and further by chemical synthesis, and among aliphatic polyesters, it can be synthesized from plant-derived raw materials, In addition, because of its excellent mechanical properties, heat resistance, and transparency, research and development are actively conducted for the purpose of developing various molded products such as films, sheets, tapes, fibers, ropes, nonwoven fabrics, and containers. . However, in applications such as wrapping film for packaging, for example, polylactic acid is not flexible enough as it is, and various softening techniques mainly by adding a plasticizer have been studied.

  For example, as a flexible polylactic acid composition, a technique using a plasticizer such as a phthalate ester that is frequently used by adding to polyvinyl chloride is disclosed (for example, see Patent Document 1). However, when a commonly used plasticizer such as a phthalate ester is added for softening, the plasticizer bleeds out immediately after the addition, but the plasticizer bleeds out over time, and the flexibility is significantly reduced. Furthermore, the addition of a plasticizer has a problem that the water vapor barrier property, which is an important characteristic when used in applications such as packaging materials, is greatly deteriorated.

  In addition, as a flexible polylactic acid composition, a technique of using a lactic acid monomer or a lactic acid oligomer as a plasticizer has been disclosed (see, for example, Patent Document 2). However, in these technologies, the poor thermal stability of the plasticizer also affects the polylactic acid, which is a polymer. The thermal stability is greatly reduced and hydrolysis is easy, and it is actually used for packaging materials. In this case, the physical properties of the molded article made of the composition may change greatly with time, and there is a great drawback that the practicality is inferior.

  Furthermore, a technique of adding a block copolymer of polyalkylene ether and polylactic acid to a plasticizer as a flexible polylactic acid composition is disclosed (for example, see Patent Document 3). However, the film made of the composition of the present technology has poor practicality because the water vapor barrier property required for packaging materials and industrial materials is greatly inferior due to the influence of the plasticizer. It was.

  As a technique limited to packaging wrap film applications, for example, a stretched film made of a composition containing a resin mainly composed of a lactic acid aliphatic polyester and a liquid additive is disclosed (for example, see Patent Document 4). . However, the liquid additive easily bleeds out, the film characteristics change over time, the bleed out liquid additive migrates to the packaged contents, and the moisture content of the contents easily out of the system. There were major problems such as volatilization and drying out.

  Furthermore, there are several examples of trying to impart functionality of a polylactic acid film by lamination. For example, a technique for laminating a low melting point polymer and a high melting point polylactic acid into two layers to impart heat sealability is disclosed (for example, see Patent Document 5).

  Also disclosed is a technique relating to a wrap film having high adhesion and gas barrier properties by laminating a layer made of polylactic acid softened with a liquid additive and a layer obtained by adding a liquid additive to an aliphatic / aromatic copolymer polyester resin. (For example, see Patent Document 6). However, this technique is still insufficient from the viewpoint of the water vapor barrier property of the composition and the bleed-out of additives and lactides.

As described above, conventionally, attempts have been made to add flexibility by adding a plasticizer to a polylactic acid resin, or improve water vapor barrier properties by lamination, but still give sufficient flexibility and When used as a film, it has not been achieved for a film in which the change in physical properties with time is suppressed by suppressing the plasticizer bleed-out or the water vapor barrier property is controlled to a level causing no practical problem.
JP-A-4-335060 JP-A-6-306264 JP-A-8-253665 JP 2000-26623 A JP-A-8-323946 JP 2002-88230 A

  In view of the background of the prior art described above, the present invention not only has excellent flexibility and adhesion required for wrap films, stretch films, bags, etc., but also has excellent water vapor barrier properties, and is also a plasticizer bleed. It is an object of the present invention to provide a polyester film in which changes in out and film properties over time are suppressed.

  The present invention employs the following means in order to solve such problems. That is, the present invention relates to a polyester comprising 50 to 95% by weight of a polylactic acid resin and 5 to 50% by weight of a plasticizer in a total of 100% by weight of the polylactic acid resin and the plasticizer, and the plasticizer includes a polylactic acid segment. A polymer plasticizer (A) having a melting point of 30 ° C. or less, and the amount of the polymer plasticizer (A) is larger than the amount of the plasticizer (B). A polyester film having a tensile modulus of 0.1 to 2 GPa.

  According to the present invention, the polyester film is not only excellent in flexibility, but also suppresses changes in physical properties over time, can maintain excellent characteristics, and is excellent in water vapor barrier properties that are important when used as a packaging material. Such a polyester film can be suitably used as a wrap film, a stretch film, a bag or the like.

  The present invention is not only excellent in the above-mentioned problems, that is, flexibility and adhesion required for a wrap film, stretch film, bag, etc., but also excellent in water vapor barrier properties, and further, plasticizer bleed out and film characteristics over time. As a result of earnest study on the polyester film in which the change is suppressed, a polylactic acid resin is used as the polyester, the specific polymer plasticizer (A) and the specific plasticizer (B) as the plasticizer, and a specific quantity relationship When it was made to contain in the form which satisfy | fills, it was discovered that this subject could be solved at once.

  That is, the polyester film of the present invention has a polylactic acid resin of 50 to 95% by mass and a plasticizer of 5 to 10% in total of 100% by mass of the polylactic acid resin and the plasticizer in order to impart unique flexibility typified by a wrap film. It is necessary to consist of 50% by mass. Furthermore, as a compounding quantity of this polylactic acid resin, Preferably it is 60-90 mass%, More preferably, it is 70-85 mass% from a viewpoint of the intensity | strength of a film, the handleability at the time of use, and barrier property. Good.

If the polylactic acid resin is less than 50% by mass, the main component in the film is a plasticizer, so that polylactic acid is present in the plasticizer, and thus the continuous phase in the film is the plasticizer. Therefore, it becomes difficult to maintain the shape as a film, and process passability and slit processability during film production become poor. In addition, there may be a case where problems such as inability to stick to and peel off from the articles to be packaged may occur or the water vapor barrier property may be poor.
On the other hand, 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. In addition, excessive force is required for packaging, which may cause problems such as damage to the package.

Here, the polylactic acid resin of the present invention is a polymer produced using L-lactic acid and / or D-lactic acid as a main starting material, and in the polyester film of the present invention, 70% by mass or more of the polylactic acid resin constituent components. Is preferably a polylactic acid resin having crystallinity starting from L- or D-lactic acid.
Polylactic acid includes poly-L-lactic acid composed of L-lactic acid, poly-D-lactic acid composed of D-lactic acid, and a racemic body thereof, and the polylactic acid resin used in the present invention is crystalline. The ratio of L-lactic acid in the lactic acid component to be constituted is preferably 99 to 70% by mass, more preferably 99 to 80% by mass.

Depending on the application, two or more homopolylactic acids having different optical purities may be used in combination for the purpose of imparting or improving necessary functions. For example, homopolylactic acid having crystallinity and amorphous Homopolylactic acid can also be used in combination.
Amorphous homopolylactic acid is a polylactic acid resin that does not exhibit a melting point and has substantially no crystal structure when subjected to differential scanning calorimetry (DSC) at a temperature elevation rate of 20 ° C./min. The crystallinity of polylactic acid is controlled by the optical purity of polylactic acid, and in the case of polylactic acid mainly composed of L-lactic acid, the proportion of D-lactic acid, that is, the amount of copolymerization of D-lactic acid increases, The melting point decreases with the decrease in the properties, and the polylactic acid does not exhibit a melting point when the copolymerization amount is approximately 10% or more.

  The proportion of amorphous homopolylactic acid may be determined within a range that does not impair the effect of the present invention, but the proportion of amorphous homopolylactic acid increases as the amount of plasticizer (B) having a melting point of 30 ° C. or lower increases. Is preferable in order to improve the bleed-out resistance. Moreover, when it is set as a laminated | multilayer film, it is preferable to raise the ratio of an amorphous homopolylactic acid in the layer containing a plasticizer (B).

  The plasticizer (B) having a melting point of 30 ° C. or lower cannot be present in the polylactic acid crystals having a dense structure, and is contained in the gaps between the molecules of the amorphous part. That is, the amount of the plasticizer (B) that can be held in the resin is determined by the amount of the amorphous part in the resin.

  In addition, in the case of being composed only of amorphous polylactic acid, since it has substantially no crystals, sufficient heat resistance such as melting at a low temperature may not be obtained. Therefore, when using amorphous polylactic acid, it is preferable to use together with crystalline polylactic acid. Normally, the higher the optical purity of homopolylactic acid, the higher the melting point. For example, poly L-lactic acid having an optical purity of 98% or higher has a melting point of about 170 ° C. In the case of imparting, it is more preferable that at least one of the polylactic acid polymers to be used contains polylactic acid having an optical purity of 95% or more.

Furthermore, it is preferable to use polylactic acid having an optical purity of 98% or more and amorphous polylactic acid in combination from the viewpoint of achieving both high heat resistance and bleed-out resistance. Although not particularly limited, for example, when both flexibility and heat resistance of 140 ° C. or higher are compatible, the amount of polylactic acid having an optical purity of 98% or more in 100% by mass of polylactic acid resin is 10 to 40% by mass, The crystalline polylactic acid is in the range of 60 to 90% by mass.
The polylactic acid of the present invention preferably has a residual lactide content in the polymer of 0.3% by mass or less in order to prevent contamination of the film forming process due to lactide bleed-out. When lactide remains in the polylactic acid in an amount of more than 0.3% by mass, the lactide may bleed out from the polylactic acid when a molded article such as a film is produced, which may contaminate the film forming process, for example. Therefore, the residual lactide content in polylactic acid is preferably 0.3% by mass or less.

  A method for producing polylactic acid is to produce L-lactide, D-lactide and DL-lactide (racemate), which are cyclic dimers, using L-lactic acid and D-lactic acid as raw materials, and ring-opening polymerization of this lactide. There are a lactide method in which a polymer is obtained with a direct polymerization method and a direct polymerization method in which a polymer is obtained by direct dehydration condensation of lactic acid in a solvent. In the present invention, polylactic acid obtained by either polymerization method is used in the same manner. It is possible. However, the direct polymerization method is more preferable in order to make the residual lactide content in the polylactic acid 0.3% by mass or less.

The polylactic acid resin of the present invention has a number average molecular weight of preferably from 20,000 to 250,000, more preferably from 40,000 to 150,000, particularly preferably from 50,000 to 110,000, from the viewpoints of overall film properties, particularly mechanical properties. It is good to be.
The polylactic acid resin of the present invention may be a copolymerized polylactic acid obtained by copolymerizing L-lactic acid and D-lactic acid with a monomer residue other than lactic acid. Examples include hydroxycarboxylic acids such as acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid, glycol compounds having ester forming ability, dicarboxylic acid compounds, and ester derivatives thereof. . Specifically, examples of the glycol compound include ethylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol and the like. Examples of the dicarboxylic acid compound include succinic acid, adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, and dimethyl ester derivatives thereof. it can. Among these, a copolymer component that does not particularly inhibit the biodegradability of polylactic acid can be preferably used. For example, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid And ethylene glycol, trimethylene glycol, tetramethylene glycol succinic acid, adipic acid, and sebacic acid.

  The plasticizer contained in the polyester film of the present invention preferably contains a polymer plasticizer (A) having a polylactic acid segment and a plasticizer (B) having a melting point of 30 ° C. or lower.

  When a polymer plasticizer that does not have a polylactic acid segment is used, problems such as changes in physical properties over time, whitening of the film surface, and contamination of articles to be packaged occur due to plasticizer exudation and extraction (bleed out). Sometimes.

  When the plasticizer (B) having a melting point of 30 ° C. or less is not contained at the same time as the polymer plasticizer (A) having a polylactic acid segment, that is, only the polymer plasticizer (A) having a polylactic acid segment is used as a plasticizer. When used as, a sufficient effect on water vapor barrier properties may not be obtained, and physical properties represented by a wrap film such as adhesion may be insufficient. In addition, when a plasticizer having a melting point exceeding 30 ° C. is used, the plasticizer becomes a substantially solid plasticizer with extremely low fluidity, so that effects such as flexibility and adhesion cannot be obtained. There may be a problem that the film is deposited on the surface and contaminates the film manufacturing process or the articles to be packaged.

  Therefore, in the polyester film of the present invention preferably used for packaging materials, the polymer plasticizer (A) having a polylactic acid segment excellent in bleed-out resistance, and a melting point of 30 ° C. for improving water vapor barrier properties and adhesiveness. It is preferable to contain the following two types of plasticizers (B) in combination.

  The amount of the plasticizer in the polyester film of the present invention is such that the polymer plasticizer (A) having a polylactic acid segment and a melting point of 30 ° C. in a total of 100% by mass of the polylactic acid resin and the plasticizer from the viewpoint of obtaining sufficient flexibility. It is preferable that the total amount of the following plasticizers (B) is 5 to 50% by mass. When the amount of the plasticizer is less than 5% by mass, sufficient flexibility cannot be obtained for the polyester film of the present invention, and when the amount of the plasticizer exceeds 50% by mass, the handleability deteriorates as a composition or film, Problems such as film blocking may occur.

  In the polymer plasticizer (A) having a polylactic acid segment of the present invention and a plasticizer (B) having a melting point of 30 ° C. or less, the amount of the polymer plasticizer (A) in the film is larger than the amount of the plasticizer (B). It is preferably contained in a form that satisfies the relationship. When the amount of the polymer plasticizer (A) is less than or equal to the amount of the liquid plasticizer (B), the flexibility is obtained, but the effect of suppressing the exudation and extraction (bleed out) of the plasticizer becomes insufficient. Problems such as changes in physical properties, whitening of the film surface, and contamination of articles to be packaged may occur.

  Furthermore, the mass ratio of the polymer plasticizer (A) having a polylactic acid segment of the plasticizer component in the film and the plasticizer (B) having a melting point of 30 ° C. or lower is 40: 1 to 1.5: 1. More preferably, it is more preferably 30: 1 to 5: 1, and particularly preferably 25: 1 to 10: 1. Further, when the film of the present invention is used as a laminated film, it is preferable that the amount of the polymer plasticizer (A) is larger than the amount of the plasticizer (B) when viewed as the whole laminate as the whole laminate. Furthermore, as a whole laminate, the mass ratio of the polymer plasticizer (A) having a polylactic acid segment as a plasticizer component in the laminate film and the plasticizer (B) having a melting point of 30 ° C. or lower is 40: 1 to 1. 5: 1 is more preferable, 30: 1 to 5: 1 is more preferable, and 25: 1 to 10: 1 is particularly preferable.

  The polymer plasticizer (A) contained in the polyester film of the present invention preferably has a polylactic acid segment. Here, the polylactic acid segment means a lactic acid block polymer composed of polylactic acid or oligolactic acid. When the polymer plasticizer (A) has a polylactic acid segment, the polylactic acid segment in the polymer plasticizer (A) becomes compatible with the polylactic acid resin as a base material, and as a result, the polymer plasticizer (A ) Has a structure in which a part thereof is taken into the polylactic acid crystal of the base material, and the anchor effect thereof can suppress bleed out of the plasticizer from the film.

  Furthermore, the polymer plasticizer (A) having such a polylactic acid segment has at least one polylactic acid segment having a molecular weight of 1500 to 10,000 in one molecule from two points of an anchor effect and a plasticizing effect. In addition, it is particularly preferable to use a polymer plasticizer (A) having a polyether segment and / or a polyester segment having a molecular weight of 1000 to 10,000.

  Here, as the polyether segment, a polyalkylene glycol such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, or a segment made of a copolymer of these polyalkylene glycols can be preferably used.

  Further, the polyalkylene glycol segment used as the polymer plasticizer (A) is preferably a polyalkylene glycol segment having low hydrophilicity from the viewpoint of good water vapor barrier properties, for example, carbon number such as polypropylene glycol and polytetramethylene glycol. It is particularly preferred that it contains 3 or more alkylene glycol components. Specifically, it is a polypropylene glycol or a polyethylene glycol / polypropylene glycol copolymer.

  Moreover, it is preferable that it is a polymeric plasticizer (A) containing a polyethyleneglycol component from the point of compatibility with a polylactic acid resin and the adhesiveness of a film.

  Therefore, depending on various properties required for the intended film application, an alkylene glycol component having 3 or more carbon atoms capable of improving water vapor barrier properties and a polyethylene glycol component capable of improving compatibility and adhesion are appropriately used in combination. It is particularly preferable to adjust.

  Next, a polymer plasticizer having one or more polylactic acid segments having a molecular weight of 1500 to 10,000 in one molecule and a polyether segment and / or a polyester segment having a molecular weight of 1000 to 10,000 (A The example of the manufacturing method of) is described.

  A commercially available polyethylene glycol having a predetermined molecular weight having hydroxyl groups at both ends and lactide which is a cyclic dimer of lactic acid are mixed at a predetermined ratio, and, for example, tin octylate is added as a polymerization catalyst. Lactide is ring-opening addition polymerized from the hydroxyl terminal to obtain an ABA type triblock copolymer covalently bonded to a polylactic acid segment-polyethylene glycol segment-polylactic acid segment. It is possible to control the molecular weight of the polylactic acid segment by controlling the addition amount of polyethylene glycol and lactide and the polymerization catalyst and the conditions of the ring-opening addition polymerization, thereby obtaining the desired polymer plasticizer (A). be able to.

  The plasticizer (B) contained in the polyester film of the present invention has a melting point of 30 ° C. or lower. This means that it has a substantially liquid or viscous liquid form at 30 ° C. and a viscosity at 30 ° C. of 1000 mPa · s or less.

  Examples of such plasticizers (B) include phthalate esters such as diethyl phthalate, dioctyl phthalate, and dicyclohexyl phthalate, di-1-butyl adipate, di-n-octyl adipate, and di-sebacate. n-butyl, aliphatic dibasic acid esters such as di-2-ethylhexyl azelate, phosphate esters such as diphenyl-2-ethylhexyl phosphate, diphenyloctyl phosphate, tributyl acetylcitrate, tri-acetylcitrate 2-ethylhexyl, hydroxy polyvalent carboxylic acid ester such as tributyl citrate, fatty acid ester such as methyl acetylricinoleate, amyl stearate, glycerin compounds such as glycerin, diglycerin, triglycerin, and these glycerins and acid components The polyhydric alcohol Steal, epoxidized soybean oil, epoxidized linseed oil fatty acid butyl ester, epoxy plasticizers such as octyl epoxy stearate, polyester plasticizers such as polypropylene glycol sebacate, polyalkylene ethers, ether esters, acrylates Oils and fats such as plasticizers, vegetable oils such as olive oil, castor oil, rapeseed oil, peanut oil, coconut oil, animal oils such as liver oil, lanolin, pork fat, beeswax, and mineral oils such as liquid paraffin and petrolatum Compounds such as fatty acids and fatty acid esters can be mentioned, and it is preferable that they are safe without problems even when used in food packaging applications.

  More preferably, natural fats and oils such as vegetable oils and these fats and oils are used from the viewpoints of excellent compatibility with polylactic acid resin, good barrier properties, and effective in improving film adhesion. It is an epoxidized compound of a fatty acid and a fatty acid ester, and epoxidized vegetable oils such as epoxidized soybean oil and epoxidized linseed oil fatty acid butyl ester are particularly preferred.

The polyester film of the present invention has a more remarkable effect in terms of balance of properties such as flexibility, adhesion, barrier properties, and bleed-out suppression by being a laminated film composed of at least two layers. Further preferred films can be obtained.
In the case of such a laminated film, the polymer plasticizer (A) having a polylactic acid segment and the plasticizer (B) having a melting point of 30 ° C. or lower may be contained in any layer, but from the viewpoint of water vapor barrier properties. , A method of providing a layer having a reduced content of a highly hydrophilic polymer plasticizer (A), or a polymer plasticizer (A) containing an alkylene glycol component having 3 or more carbon atoms with good water vapor barrier properties The structure which has the layer which raised the ratio of plasticizers (B), such as epoxidized vegetable oil, is preferable.

Moreover, it is preferable to set it as the structure which has the layer which raised the ratio of the polymeric plasticizer (A) and plasticizer (B) which contain a polyethyleneglycol component in a surface layer from the point of adhesiveness. More preferably, when the laminated film is composed of two layers, one layer is a laminated film having a higher plasticizer (B) content than the other layer, and the laminated film is composed of three or more layers. Is that the surface layer is a laminated film having a higher plasticizer (B) content than the inner layer. The number of laminated layers is particularly preferably 3 or more layers that have a structure with no difference in physical properties such as adhesion between the front and back of the film.
Furthermore, it is preferable that the plasticizer (B) content of the layer constituting the outermost layer of the laminated film is greater than that of the inner layer. Thereby, even if it is a film with the same plasticizer (B) content when seen as a whole film, the plasticizer (B) is added to the outermost layer that most affects the water vapor barrier property and adhesion. This is because a film having a plasticizer (B) content in the layer constituting the outermost layer more than the inner layer can be a film having excellent water vapor barrier properties and adhesion.

For example, a layer containing a polymer plasticizer (A) having a polylactic acid segment (A layer) and a melting point obtained by separating a polymer plasticizer (A) and a plasticizer (B) having a melting point of 30 ° C. or less into separate layers A laminated film of two or more layers of AB type and BAB type each having a layer (B layer) containing a plasticizer (B) of 30 ° C. or less can be mentioned. In this film, since the B layer has a higher plasticizer (B) content than the A layer, the B layer is excellent in water vapor barrier properties and / or adhesiveness. It can be set as the film which can be used conveniently for.
For example, when three layers are stacked, the inner layer means a central layer sandwiched between two layers. And an inner layer provides a softness | flexibility and barrier property as an A layer containing the polyethyleneglycol which has a polylactic acid segment, and / or C3 or more alkylene glycol polymer plasticizer (A). And a surface layer provides barrier property and adhesiveness as B layer made into the layer containing a plasticizer (B) by reducing the amount (A) of polymer plasticizers compared with an inner layer. By making these A layer and B layer into a BAB type | mold laminated film, since characteristics, such as a softness | flexibility, adhesiveness, barrier property, and bleed-out resistance, can be achieved at a high level, it is especially preferable.

In the polyester film of the present invention, an antioxidant, an ultraviolet stabilizer, a coloring inhibitor, a matting agent, a deodorant, a flame retardant, a weathering agent, an antistatic agent, as long as the effects of the present invention are not impaired. As necessary, inorganic fine particles, organic particles, or organic compounds may be added as a release agent, antioxidant, ion exchange agent, or coloring pigment.
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.

  Moreover, from the point which makes transparency favorable, the particle | grains which have a refractive index close | similar to polyester used as a base material are preferable, and particles, such as a silica, colloidal silica, a polymethylmethacrylate, are more preferable at such a point. Moreover, as particles used for the polyester film of the present invention, it is preferable to select naturally occurring inorganic particles or biodegradable particles. The average particle diameter 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.

  The polyester film of the present invention preferably has a tensile modulus of 0.1 to 2 GPa obtained by a tensile test at 23 ° C. That is, when the tensile elastic modulus of the film is less than 0.1 GPa, elongation and slackening may occur in film formation and processing steps, and handling properties, process passability, and slit processability may be poor. In addition, when used as a wrap film, the film may be deformed before it wraps an article such as a container or food, and problems such as inability to efficiently wrap may occur. Moreover, when this tensile elasticity modulus exceeds 2 GPa, it does not deform | transform following the shape of the articles | goods and foodstuff to package, and sufficient adhesiveness may not be obtained. Further, excessive force is required for packaging, and problems such as damage to the package may occur. A more preferable range of the tensile modulus is 0.1 to 1.5 GPa, more preferably 0.15 to 1.2 GPa, and particularly preferably 0.2 to 1 GPa.

  In the present invention, the term “tensile test” means a test performed under a tensile speed of 300 mm / min using a Tensilon universal testing machine in accordance with JIS K7161 and JIS K7127 in an atmosphere of 23 ° C. In the present invention, the tensile elastic modulus means the difference in stress between two points on the straight line by using the first linear portion of the stress-strain curve obtained in the above tensile test. This is the value obtained by dividing.

The polyester film of the present invention preferably has a moisture permeability of 0 to 40 g / (m ² · day), which is an indicator of water vapor barrier properties, from the viewpoint of use as a packaging film for storage of food containing moisture.
When the moisture permeability exceeds 40 g / (m ² · day), the food may be dried during storage of the food containing moisture, which is not preferable. Also, the smaller the value of moisture permeability, the better the water vapor barrier property. However, in reality, it is difficult to achieve less than 0.01 g / (m ² · day), but 40 g / (m ² · day) or less. For example, it is sufficient for use as a packaging film for food preservation.

More preferably, it is 0-35 g / (m < ² > * day), More preferably, it is 0-30 g / (m < ² > * day), It is especially preferable that it is 0-25 g / (m < ² > * day).

Here, moisture permeability refers to the amount of permeation per day obtained by placing pure water in an aluminum container, sealing the open part with a film, storing it in a refrigerator for 3 days, measuring the change in weight before and after storage. It is.
In order to set the moisture permeability to 0 to 40 g / (m ² · day), flat particles having an irregularity (major axis / minor axis) of 5 to 1000 and an average major axis of 0.1 to 10 μm are 0.01. The method of containing 10 mass% can be preferably used.

  From the viewpoint of compatibility between water vapor barrier properties and film transparency, and prevention of cleavage of the film by flat particles, the degree of irregularity is more preferably 5 to 500, and particularly preferably 7 to 100. Further, the average major axis of the flat particles is more preferably 0.3 to 5 μm, and particularly preferably 0.5 to 3 μm. As the flat particles, layered inorganic particles collected from natural minerals can be preferably used.

  Examples of such layered inorganic particles include kaolin, talc, mica, barite, and the like, but talc is particularly preferably used from the viewpoint of water vapor barrier properties. In order to satisfy both transparency and moisture permeability of the film preferably, the content is particularly preferably 0.5 to 3% by mass.

  Moreover, you may use together the method of containing 0.1-5 mass parts of wax compounds with respect to a total of 100 mass parts of polylactic acid resin and a plasticizer from the point which improves water vapor | steam barrier property. By containing the wax compound, the hydrophilicity of the film is reduced, the dispersibility of the inorganic particles is increased, and a more remarkable water vapor barrier effect can be obtained. In consideration of the handleability of the film, it is more preferably 0.2 to 2 parts by mass, and particularly preferably 0.3 to 1.5 parts by mass.

  Examples of the wax compound include carnauba wax, candelilla wax, rice wax, pentaerythritol full ester, behenyl behenate, partyl myristate, stearyl stearate, olefin wax, and the like. Uba wax, candelilla wax, rice wax and the like are particularly preferable.

  The method of adding such a wax compound is not limited to the method exemplified below. For example, a twin screw extruder is employed as a melt extruder in film production, and a wax together with a polylactic acid resin and a plasticizer. A method of melt-extruding a compound, a method of preparing a master batch by mixing with a polylactic acid resin or a polymer plasticizer (A) in advance with a twin screw extruder, and subjecting it to melt-extrusion, and further a polymerization step of the polylactic acid resin. A method of obtaining a master batch by adding a wax compound so as to have a concentration of and polymerizing polylactic acid in the presence of the wax compound can be employed. A method of preparing a master batch in advance is particularly preferable because the manufacturing apparatus is not limited. Since these wax components have a good compatibility with fats and oils and compounds such as fatty acids and fatty acid esters constituting the fats and oils, it is necessary to use them in combination with such plasticizers (B). Is particularly preferable in terms of the properties and barrier properties.

  When the polyester film of the present invention is used as a packaging film such as a wrap film, the haze is preferably 0.1 to 10%, more preferably 0.1 to 5% so that the contents can be easily distinguished. More preferably, it is 0.2 to 3%, and particularly preferably 0.2 to 1%.

  Needless to say, it is important to increase the compatibility between the polylactic acid resin constituting the film and the plasticizer as a method for adjusting the film haze to 0.1 to 10%. It is important to control the amount and combination of agents.

  In some cases, such as garbage bags and agricultural multi-films, a certain degree of concealment is required, a case where a low light transmittance is preferable, or a case where a high absorption factor such as sunlight is preferable, In such applications, for example, a color pigment typified by carbon black or titanium oxide may be added as necessary.

  Although the manufacturing method of the polyester film of this invention is illustrated concretely below, the manufacturing method of the film of this invention is not limited to this. First, as a method for producing a polylactic acid resin, for example, polymerization of poly-L-lactic acid can be performed as follows.

  0.02 parts by mass of tin octylate is added to 100 parts by mass of commercially available L-lactide and polymerized at 190 ° C. for 15 minutes in a nitrogen atmosphere to obtain a precursor poly-L-lactic acid. After making this precursor poly L-lactic acid into chips, poly L-lactic acid suitable for film production can be obtained by solid-phase polymerization at 140 ° C. for 3 hours in a nitrogen atmosphere.

  Moreover, the synthesis | combination of the polymeric plasticizer (A) which can be preferably used by this invention can be performed as follows. By mixing 71 parts by mass of a commercially available polyethylene glycol having an average molecular weight of 10,000, 29 parts by mass of L-lactide and 0.02 parts by mass of tin octylate and polymerizing at 160 ° C. for 2 hours in a nitrogen atmosphere, An ABA type triblock copolymer having a poly L-lactic acid unit having an average molecular weight of 2,000 can be obtained.

  The film of the present invention can be produced using the polylactic acid resin and plasticizer obtained as described above. In order to suppress degradation of the polylactic acid resin and plasticizer used and generation of decomposition products, vacuum drying at 90 ° C. to 110 ° C., a high vacuum of 10 Torr or less, and a drying time of 6 hours or more Is preferred.

  In the production of a stretched film, for example, the above-mentioned polyester dried under vacuum can be melt-extruded into a sheet form from a slit-shaped base by a known method, but the thermal decomposition is suppressed and a low molecular weight product such as lactide is used. From the viewpoint of suppressing the increase, the extrusion temperature is preferably lower, and the residence time is preferably shorter. Specifically, the temperature of the extruder, polymer piping, die, etc. is preferably 200 ° C. or lower, more preferably 190 ° C. or lower, and more preferably 180 ° C. or lower. The residence time from when the polylactic acid resin composition is melted in the extruder until it is discharged from the die is preferably 20 minutes or less, more preferably 10 minutes or less, and more preferably 5 minutes or less. Is more preferable.

  The extruded sheet-like melt is brought into close contact with the casting drum and solidified by cooling to obtain an unstretched film. When a plasticizer is added to a polylactic acid resin, for example, a blend chip obtained by mixing a polylactic acid resin master chip and a polylactic acid resin homochip containing a high concentration of plasticizer is supplied to an extrusion system of a film forming machine such as an extruder. However, in order to minimize the thermal deterioration of the composition and reduce the lactide content, the raw material dried under vacuum is used, and a twin-screw extruder is used. A method in which a plasticizer in a liquid state by heating, for example, is heated to the polylactic acid polymer melted therein in a continuous manner while being measured and melt-kneaded is preferable. Further, a method is preferred in which a vent port is provided in the middle of the twin screw extruder, the vent port is decompressed, and melt kneading while removing moisture and low molecular weight components such as oligomers generated during melting.

  The unstretched film obtained by such a method can be obtained by continuously stretching in at least one direction. As a method for producing a stretched film, a method such as an inflation method, a sequential biaxial stretching method, a simultaneous biaxial stretching method, or the like can be used. The film is stretched in the longitudinal direction by roll stretching using a speed difference, and then stretched in a direction perpendicular to the first-stage stretching direction in a tenter having a continuous clip, followed by heat treatment in the tenter and / or after winding. Can be applied.

  The stretching conditions of the film can be adjusted as appropriate according to the desired heat shrinkage characteristics, dimensional stability, strength, elastic modulus, etc., and can be carried out by any method. It is preferable to become. By stretching and crystallizing the polylactic acid polymer as a base material by stretching, and simultaneously promoting the incorporation of the polylactic acid segment of the polymer plasticizer (A) into the crystal, It is preferable because exudation and extraction (bleed out) 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 not less than the glass transition temperature of the polyester used and not more than the crystallization temperature in terms of biaxial stretching properties and transparency of the film, and the stretching ratio is 1.1 times in the longitudinal direction and the width direction, respectively. It can be set within a range of 10 to 10 times, and either the longitudinal direction or the width direction may be increased or may be 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. In some cases, deterioration of the transparency of the film may occur, and in the case of sequential biaxial stretching, the stretchability in the second direction may be lowered, so that it is preferable to adjust appropriately.
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 condition is preferably carried out at a higher temperature in the range from the glass transition temperature of the polyester to the melting point from the viewpoint of film strength and dimensional stability, specifically 40 to 90 ° C.

  Further, the stretching speed can be appropriately adjusted within a range of 100 to 50000% / min. Further, it is more preferable to perform heat treatment at 100 ° C. or higher for 10 seconds or longer for the purpose of stabilizing the structure of crystals and plasticizer in the film and reducing low molecular weight components such as oligomer components in the film.

Further, the heat treatment may be performed by relaxing in the film longitudinal direction and the width direction.
When a specific elongation such as a stretch film is required, the draw ratio and heat treatment temperature are preferably adjusted as appropriate. The draw ratio is 1 to 10 times the area magnification, and the heat treatment temperature is 120 ° C. or less and 20 seconds or less. A short heat treatment is preferable.

  The polyester film of the present invention expresses a more remarkable effect in terms of balance of properties such as flexibility, adhesion, and barrier properties, and suppression of bleed out, so that it is a laminated film composed of at least two layers. Is preferred. As a method for producing a laminated film, a method of obtaining a laminated film by laminating polymers melted by separate extruders in a feed block installed on top of a T die or a round die and extruding the die as it is is preferable. In addition, it is particularly preferable to use an ABA or BAB type three-layer laminated film from the viewpoint of reducing the difference in physical properties between the front and back sides and achieving both flexibility and film forming stability. The film structure is not limited to this, and may be a laminated structure having more than three layers as required, and the lamination thickness ratio of each layer can be arbitrarily set.

  Moreover, it is preferable that the film thickness of the polyester film of this invention is 5-100 micrometers from a viewpoint used as a film for packaging, and it is more preferable if it is 7-60 micrometers. It is preferable that it is 7-15 micrometers from the point which makes the shape followability at the time of wrapping articles | goods especially at the point used as a wrap film.

  The polyester film of the present invention is preferably subjected to surface treatment such as corona discharge treatment or plasma treatment from the viewpoint of enhancing the functionality of the film surface. Further, a different adhesive resin or the like may be coated in the film production in-line or offline, or a metal compound may be deposited and used.

  The polyester film of the present invention not only excels in flexibility and adhesion, but also retains excellent properties by suppressing changes in physical properties over time. It can be suitably used as a film, stretch film or bag.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, it is not limited by a following example. The characteristics were measured and evaluated by the following methods.
(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.

In the case of a laminated film, using a transmission electron microscope (H-7100FA type manufactured by Hitachi), a sheet cross section is obtained by an ultrathin section method (stained with RuO _{4 as} necessary) at an acceleration voltage of 100 kV and a magnification of 10,000. Observation was performed at a magnification of 100,000 times, the interface was grasped, the laminated structure was confirmed, and the analysis was cut out for each layer. Moreover, if necessary, microscopic IR analysis of the cross section of the film was performed by the film surface or the frozen ultrathin section method.
(2) Number average molecular weight [Mn] of film constituents
A sample was dissolved in a THF (tetrahydrofuran) solution so as to be 1 mg / cc, and measured in terms of polystyrene using GPC (gel permeation chromatography). The instrument is LC-10A series manufactured by Shimadzu Corporation, 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- manufactured by Showa Denko KK 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 as a 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 by cubic approximation.
(3) 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 tester UTC-100 (Orientec Co., Ltd.) in an atmosphere of 23 ° C. according to JIS K7161 and JIS K7127. It was. Next, using the first linear part of the stress-strain curve obtained in the tensile test, the difference in stress between two points on the straight line is divided by the difference in strain between the same two points, and a total of five tests are performed. Then, an average value was obtained, and this was taken 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.
(4) Barrier property: moisture permeability Based on the water method (A-2 method) of JIS L1099 (established in 1993), evaluation was performed under the following conditions. About 20 g of pure water is put in an aluminum container having an inner diameter of 60 mm, a film sample is mounted on the open part, and a packing and a ring are attached and fixed with a thumbscrew. In this state, the weight is weighed and then left for 3 days (72 hours) in a constant temperature and humidity chamber set to a temperature of 2 ° C. and a humidity of 90%. After 72 hours, the weight is weighed again, and the moisture permeability is calculated from the change in weight.

Moisture permeability (g / (m ² · day)) = weight change before and after standing (g) / (sample area (m ² ) × 3 (day))
Here, the sample area is 2.83 × 10 ⁻³ m ² from the inner diameter of the container.

A: Value of moisture permeability of 30 g / (m ² · day) or less.

○: The moisture permeability is greater than 30 g / (m ² · day) and is a numerical range of 40 g / (m ² · day) or less.

△: moisture permeability is greater than 40g / ^{(m 2} · day), 60g / ^{(m 2} · day) the following numerical ranges.

X: Value with a water vapor permeability larger than 60 g / (m ² · day).
(5) Transparency: Haze value of film A film sample was cut into a longitudinal direction of 40 mm and a width direction of 30 mm, and conditioned for 24 hours in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH. This sample was subjected to haze measurement using a haze meter (HGM-2GP manufactured by Suga Test Instruments Co., Ltd.) in an atmosphere of 23 ° C. based on JIS K 7105 (1985). The measurement was performed at three arbitrary locations, the average value was adopted, and evaluation was performed according to the following criteria.

  The film haze value is obtained by the above measuring instrument, and is a value obtained by dividing the scattered light transmittance by the total light transmittance and multiplying by 100.

  A: The haze is less than 3%.

  ○: Haze in the range of 3% or more and less than 5%.

  Δ: Haze in the range of 5% or more and less than 10%.

X: Haze exceeds 10%.
(6) Bleed-out resistance: Weight change rate after hot water treatment [%]
For press sheets or biaxially stretched film samples that had been conditioned for 1 day or more in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH in advance, the weight before treatment was measured, followed by treatment in distilled water at 90 ° C. for 30 minutes. Thereafter, the moisture was adjusted again under the same conditions as before the treatment, and the weight was measured. The weight change rate was calculated as a ratio of the weight change (decrease) before and after the treatment to the weight before the treatment, and was evaluated according to the following criteria.

  A: Weight change rate is less than 2%.

  ○: The weight change rate is in the range of 2% or more and less than 3%.

  Δ: Weight change rate is in the range of 3% or more and less than 4%.

X: Weight change rate is 4% or more.
(7) Adhesion: Adhesion strength [N / cm]
Samples were cut two pieces of width 5 cm × length 10cm and overlapping the ends 10 mm ^2, after a load is applied 500 g 1 minute, a tensile tester using a measurement temperature 23 ° C., subjected to a tensile test at a rate of 100 mm / min The value obtained by dividing the maximum load by the sample width was defined as the adhesion force (N / cm), and the following criteria were used for evaluation.
In the measurement, the number of n was set to 5, and the average value was obtained as the adhesion (N / cm).

  A: Adhesive strength is 4 N / cm or more.

  ○: The adhesion is in the range of 3 N / cm or more and less than 4 N / cm.

  (Triangle | delta): The range whose adhesive force is 2 N / cm or more and less than 3 N / cm.

X: Adhesion force is less than 2 N / cm.
(8) Comprehensive evaluation Transparency, flexibility, bleed-out resistance, barrier properties, and adhesion are comprehensively evaluated, and all items are evaluated as ○ or ◎ comprehensive evaluations ◎, all items are △ to ◎ Evaluations were evaluated as comprehensive evaluation ○, and those with evaluation were evaluated as comprehensive evaluation ×.
(Manufacture of raw material resin)
The polylactic acid resin and polymer plasticizer (A) used for film formation were prepared as follows.
(Polylactic acid P1)
0.01 parts by mass of tin octylate is added to 100 parts by mass of L-lactide and polymerized at 185 ° C. for 30 minutes in a nitrogen atmosphere to obtain a precursor poly-L-lactic acid. After this precursor poly-L-lactic acid was chipped, solid phase polymerization was carried out at 140 ° C. for 3 hours in a nitrogen atmosphere to obtain polylactic acid P1 having a number average molecular weight of 100,000. When the polylactic acid P1 was subjected to DSC measurement, the polylactic acid P1 had crystallinity, the crystallization temperature was 130 ° C., and the melting point was 171 ° C.
(Polylactic acid P2)
By adding 0.02 parts by mass of octylic acid to 35 parts by mass of DL-lactide to 65 parts by mass of L-lactide, polymerizing at 185 ° C. for 60 minutes in a nitrogen atmosphere, and then discharging onto strands to form chips. Polylactic acid P2 having an average molecular weight of 90,000 was obtained. When DSC measurement was performed on polylactic acid P2, polylactic acid P2 did not exhibit crystallinity, and crystallization temperature and melting point were not observed.
(Polymer plasticizer (A) 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 polymer plasticizer (A) S1 having a polylactic acid segment having an average molecular weight of 2500 was obtained.
(Polymer plasticizer (A) S2)
By mixing 62 parts by mass of polypropylene glycol having a number average molecular weight of 10,000, 38 parts by mass of L-lactide and 0.013 parts by mass of tin octylate and polymerizing at 160 ° C. for 2.5 hours in a nitrogen atmosphere, both ends of polypropylene glycol The polymer plasticizer (A) S2 having a polylactic acid segment with a number average molecular weight of 3000 was obtained.
(Polymer plasticizer (A) S3)
To 65 parts by mass of a polypropylene glycol / ethylene glycol block copolymer having a number average molecular weight of 10,000 and 35 parts by mass of L-lactide prepared by addition reaction of ethylene oxide to both ends of polypropylene glycol having a number average molecular weight of 4,000. On the other hand, 0.015 parts by mass of tin octylate is mixed, and polymerized in a reaction vessel equipped with a stirrer at 160 ° C. for 2.5 hours in a nitrogen atmosphere, and has a polylactic acid segment with a number average molecular weight of 2700, polypropylene glycol ethylene A block copolymer of glycol and polylactic acid, a polymer plasticizer (A) S3 was obtained.
(Polymer plasticizer (A) S4)
50 parts by mass of a polypropylene glycol / ethylene glycol block copolymer having a number average molecular weight of 10,000 and 50 parts by mass of L-lactide prepared by addition reaction of ethylene oxide on both ends of polypropylene glycol having a number average molecular weight of 4,000 On the other hand, 0.02 part by mass of tin octylate was mixed, polymerized in a nitrogen atmosphere at 160 ° C. for 3 hours in a reaction vessel equipped with a stirrer, and having a polylactic acid segment having a number average molecular weight of 5000, A block copolymer of polylactic acid and a polymer plasticizer (A) S4 were obtained.
(Plasticizer (B) L1)
Asahi Denka Kogyo Co., Ltd. epoxidized linseed oil butyl ester plasticizer Adekasizer (registered trademark) “D-178” was used as the plasticizer (B) L1. This plasticizer had a melting point of 2 ° C. and a viscosity at 30 ° C. of 25 mPa · s.
(Plasticizer (B) L2)
The epoxidized soybean oil plasticizer “SO” manufactured by Daihachi Chemical Co., Ltd. was used as the plasticizer (B) L2. This plasticizer had a melting point of about 3 ° C. and a viscosity at 30 ° C. of 300 mPa · s.
(Plasticizer (B) L3)
The ether ester plasticizer “RS-1000” manufactured by Asahi Denka Kogyo Co., Ltd. was used as the plasticizer (B) L3. This plasticizer had a melting point of −41 ° C. and a viscosity at 30 ° C. of 40 mPa · s.
(Example 1)
A mixture of 20 parts by mass of the polylactic acid resin (P1), 55 parts by mass of the polylactic acid resin (P2), 15 parts by mass of the polymer plasticizer (A) (S1), and 10 parts by mass of the plasticizer (B) (L1) is 100 ° C. And dried under reduced pressure under a vacuum of 5 torr for 6 hours, and then subjected to a twin-screw kneading extruder having a cylinder temperature of 190 ° C. to melt-knead and homogenize to obtain a chipped composition. The resulting composition was transparent.

  This composition was dried under reduced pressure under a vacuum of 5 torr at 80 ° C. for 24 hours, then supplied to a single screw extruder with a screw diameter of 30 mm, and extruded into a film at an extruder cylinder temperature of 190 ° C. and a T die die temperature of 190 ° C. An unstretched film was produced by electrostatic application casting on a drum cooled to 5 ° C.

After continuously stretching 3.0 times between 55 ° C heating rolls in the longitudinal direction, the obtained uniaxially stretched film is gripped with a clip and guided into a tenter, and heated in the transverse direction while being heated at a temperature of 60 ° C. The film was stretched 8 times and fixed in the width direction at 120 ° C. for 10 seconds to obtain a biaxially stretched polyester film having a thickness of 12 μm. 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 polyethylene glycol having a number average molecular weight of 8000 having no polylactic acid segment was used as the polymer plasticizer (A). 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 20 parts by mass of polylactic acid resin (P1), 55 parts by mass of polylactic acid resin (P2), and 25 parts by mass of polymer plasticizer (A) (S1) was used. Created. 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 25 parts by mass of polylactic acid resin (P1), 55 parts by mass of polylactic acid resin (P2), and 20 parts by mass of plasticizer (B) (L3) was used. . The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 4)
Use a mixture of 20 parts by mass of polylactic acid resin (P1), 55 parts by mass of polylactic acid resin (P2), 10 parts by mass of polymer plasticizer (A) (S1), and 15 parts by mass of plasticizer (B) (L1). Except for the above, a film was prepared in the same manner as in Example 1. The evaluation results of the obtained film are shown in Table 1.
(Example 2)
A layer A and a layer B were laminated in a B / A / B structure.
Layer A is a mixture of 15 parts by mass of polylactic acid (P1), 55 parts by mass of polylactic acid (P2), and 30 parts by mass of polymer plasticizer (A) (S1), which is supplied to a vent type twin screw extruder and vacuumed. Melt extrusion was performed while maintaining the vacuum at 1 torr by reducing the pressure from the vent hole.

  On the other hand, in layer B, 20 parts by mass of polylactic acid resin (P1), 65 parts by mass of polylactic acid resin (P2), and 15 parts by mass of plasticizer (B) (L1) are mixed and supplied to the vent type twin screw extruder. Then, melt extrusion was performed.

The molten mixed resin was removed with a 400-mesh screen to remove foreign matters and the like, and then a B / A / B three-layer laminated structure was formed with a feed block installed on the upper part of the die, and was discharged from a T die onto a 5 ° C. cooling roll. The lamination was performed so that the lamination thickness ratio was 1: 8: 1. The discharged polymer was made to adhere to the cooling roll by electrostatic application using a wire electrode to obtain an unstretched film. Subsequently, it heated to 55 degreeC using the heating roll, and extended | stretched 3 times in the film longitudinal direction using the peripheral speed difference of the roll. Next, the film was introduced into a tenter-type transverse stretching machine, and stretched 3 times in the width direction at 60 ° C. Furthermore, heat treatment was performed at 120 ° C. for 10 seconds in the tenter as it was to obtain a polylactic acid film having a film thickness of 10 μm.
(Example 3)
A layer A and a layer B were laminated in a B / A / B structure. Layer A is composed of 14 parts by mass of polylactic acid (P1), 54 parts by mass of polylactic acid (P2), 16 parts by mass of polymer plasticizer (A) (L1), and 16 parts by mass of polymer plasticizer (A) (L2). Layer B is 15 parts by mass of polylactic acid resin (P1), 65 parts by mass of polylactic acid resin (P2), and 20 parts by mass of plasticizer (B) (L1). : A polylactic acid film having a film thickness of 10 μm was obtained under the same conditions as in Example 2 except that the ratio was 18: 1.
Example 4
A layer A and a layer B were laminated in a B / A / B structure. Layer A is composed of 15 parts by mass of polylactic acid (P1), 60 parts by mass of polylactic acid (P2), 15 parts by mass of polymer plasticizer (A) (S2), and 10 parts by mass of plasticizer (B) (L3). The layer B was used in Examples except that 20 parts by mass of the polylactic acid resin (P1), 55 parts by mass of the polylactic acid resin (P2), and 25 parts by mass of the polymer plasticizer (A) (S1) were used in the same manner. A polylactic acid film having a film thickness of 10 μm was obtained under the same conditions as in 2.
(Example 5)
Layer A is a mixture of 20 parts by mass of polylactic acid (P1), 55 parts by mass of polylactic acid (P2), and 25 parts by mass of polymer plasticizer (A) (S3), and layer B is a polylactic acid resin (P1) 20 Mass parts, 55 parts by mass of polylactic acid resin (P2), 15 parts by mass of polymer plasticizer (A) (S1), and 10 parts by mass of plasticizer (B) (L1) were used in the same mixture.

  Each is supplied to an extruder, and is extruded into a tube shape from an annular die having a die diameter of 80 mm and a die slit gap of 1 mm so that layers A and B are B / A / B and the lamination thickness ratio is 1: 8: 1. The film was brought into contact with the inner surface of the sizing ring that had been passed through and overflowed at 0 ° C., and cooled to obtain an unstretched film having a folding width of 140 mm.

The unstretched film was preheated at 50 ° C. for 5 seconds with a difference in peripheral speed between the upper and lower nip rolls, and then 3.0 times in the longitudinal direction and 2.8 in the width direction due to the pressure of the air enclosed in the tube. The film was biaxially stretched twice and solidified by blowing cooling air at 20 ° C. with an air ring to obtain a stretched film. Further, one end face of the film was slit, developed, and heat-treated with a heating roll at 100 ° C. while being held with a nip roll to obtain a polylactic acid film having a film thickness of 10 μm.
(Example 6)
The same raw materials as in Example 5 were used, and each was supplied to an extruder. Die diameter 80 mm, die slit gap 0 so that layers A and B were B / A / B and the lamination thickness ratio was 1: 8: 1. Extruded into a tube shape from an .8mm annular die and pulled by the lower nip roll, and simultaneously biaxially stretched 3.0 times in the longitudinal direction and 2.4 times in the width direction by the air pressure enclosed in the tube. And solidified by blowing cooling air at 20 ° C. to obtain an inflation stretched film.

Further, one end face of the film was slit, developed, and heat-treated with a heating roll at 80 ° C. while being held with a nip roll to obtain a polylactic acid film having a film thickness of 15 μm.
(Example 7)
Layer A is a mixture of 10 parts by mass of polylactic acid (P1), 45 parts by mass of polylactic acid (P2), and 45 parts by mass of polymer plasticizer (A) (S4). Layer B is 20 parts of polylactic acid resin (P1). A polylactic acid film having a film thickness of 10 μm is obtained in the same manner as in Example 5 except that 15 parts by mass of polylactic acid resin (P2) and 15 parts by mass of plasticizer (B) (L1) are mixed and used. It was.
(Example 8)
A polyaluminum having a film thickness of 10 μm was prepared in the same manner as in Example 2 except that 1 part by weight of the wax compound was added to 100 parts by weight of the total amount of the polylactic acid resin and the plasticizer in each of the layers A and B. A lactic acid film was obtained.
Example 9
Layer A is 15 parts by mass of polylactic acid (P1), 55 parts by mass of polylactic acid (P2), 15 parts by mass of polymer plasticizer (A) (S1), 15 parts by mass of polymer plasticizer (A) (S2), One part by weight of carnauba wax and 4 parts by weight of talc (average major axis 1.0 μm, degree of irregularity 10) particles are mixed with 100 parts by weight of the polylactic acid resin and plasticizer, and layer B is made of polylactic acid resin (P1 ) 15 parts by mass, 65 parts by mass of polylactic acid resin (P2), 20 parts by mass of plasticizer (B) (L1), and 1 part by mass of carnauba wax with respect to 100 parts by mass of polylactic acid resin and plasticizer, talc ( Polylactic acid film having a film thickness of 18 μm in the same manner as in Example 6 except that 4 parts by mass of particles having an average major axis of 1.0 μm and an irregularity of 10) are used in the same manner and the lamination thickness ratio is 1: 18: 1. Got.

The symbols in Table 1 have the following meanings.
P1: Polylactic acid P1
P2: Polylactic acid P2
S1: Polymer plasticizer (A) S1
S2: Polymer plasticizer (A) S2
S3: Polymer plasticizer (A) S3
S4: Polymer plasticizer (A) S4
PEG: Polyethylene glycol L1: Plasticizer (B) L1
L2: Plasticizer (B) L2
L3: Plasticizer (B) L3
WAX: carnauba wax particles: talc particles From Table 1, in Examples, in addition to excellent flexibility, transparency, bleed-out resistance, and adhesion, water vapor barrier properties were extremely excellent.

  On the other hand, in Comparative Example 1, since it was not a polymer plasticizer (A) having a polylactic acid segment, the bleed-out resistance was inferior and the water vapor barrier property was also inferior.

  Further, in Comparative Example 2, although the bleed-out resistance was good, only the polymer plasticizer (A) having a polylactic acid segment was contained as a plasticizer, so that the water vapor barrier property was poor.

  In Comparative Example 3, the polymer plasticizer (A) having a polylactic acid segment is not included, and in Comparative Example 4, the polymer plasticizer (A) having a polylactic acid segment is less than the plasticizer (B). Therefore, the flexibility and transparency were good, but the bleed-out resistance was poor.

  When the water vapor barrier property is inferior as in Comparative Examples 1 to 3, problems such as drying and hardening occur when food such as rice balls are wrapped.

  Moreover, the film of Example 6 had a tensile elongation of 420% on average in the longitudinal direction and the width direction, and had good characteristics as a stretch film.

  In addition, the film of Example 9 is slightly inferior in adhesion as a wrap film, but has good barrier properties and good film slipperiness and heat sealability, so that it has flexibility and barrier. It had good characteristics as a packaging film such as a bag having good properties.

  The polyester film of the present invention can be suitably used as a packaging film for articles such as wrap films, stretch films, and bags and foods.

Claims (8)

  A polymer plasticizer comprising polylactic acid resin and plasticizer in a total of 100% by mass of polylactic acid resin and 50 to 95% by mass of polylactic acid resin and 5 to 50% by mass of plasticizer, wherein the plasticizer has a polylactic acid segment (A) and a plasticizer (B) having a melting point of 30 ° C. or less, and the amount of the polymeric plasticizer (A) is larger than the amount of the plasticizer (B). 0.1-2 GPa polyester film.   The polymer plasticizer (A) has at least one polylactic acid segment having a molecular weight of 1500 to 10,000 in one molecule and a polyether segment and / or a polyester segment having a molecular weight of 1,000 to 10,000. The polyester film according to claim 1.   The polyester film according to claim 1 or 2, which is a laminated film having at least two layers.   The polyester film according to claim 3, wherein the film is composed of two layers, and one layer has a plasticizer (B) content higher than that of the other layer.   The polyester film according to claim 3, wherein the film comprises three or more layers, and the surface layer has a plasticizer (B) content higher than that of the inner layer.   The polyester film according to any one of claims 1 to 5, wherein the plasticizer (B) is an epoxidized vegetable oil-based plasticizer.   The polyester film according to any one of claims 1 to 6, comprising a polymer plasticizer (A) having an alkylene glycol component having 3 or more carbon atoms as the polymer plasticizer (A). Moisture permeability is 0~40g / ^{(m 2} · day), polyester film according to any one of claims 1 to 7.