JP2005139280A - Polyester resin composition and film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polyester resin composition having an excellent heat resistance, film moldability and productivity, and to prepare a film, specifically a flexibility-imparted film which has a sufficient flexibility and further is a controlled in volatilization, leaching and bleed-out of a plasticizer in addition to its excellent heat resistance, film moldability and productivity. <P>SOLUTION: The polyester resin composition is a polyester mainly composed of a polylactic acid-based polymer, contains an alkali metal element and/or an alkaline earth metal element and has a melt resistivity at 200°C of 5×10<SP>6</SP>-5×10<SP>9</SP>Ωcm. The polyester film is composed of the polyester resin composition. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polyester resin composition and a film mainly composed of a polylactic acid-based polymer, and is excellent in heat resistance and film moldability, enabling high-speed and efficient film production, that is, excellent in productivity and flexible. In addition to excellent heat resistance, film formability, and productivity, it has excellent flexibility and plasticizer volatilization, exudation, and extraction (bleed out) problems. The present invention relates to a polyester resin composition and a film suitable as a packaging film for goods and food such as a wrap film having no utility.

  Conventionally, plastic waste has been mainly processed by incineration or landfill, but the generation and discharge of harmful by-products by incineration, deterioration of incinerators due to high combustion heat, reduction of landfill, and environmental pollution by illegal dumping, etc. The problem is becoming apparent. As social concerns about such plastic waste disposal problems increase, research and development of biodegradable plastics that are decomposed by enzymes and microorganisms has been actively carried out. Has been. Recently, polylactic acid is an example of a biodegradable aliphatic polyester that has been particularly actively researched and developed.

  Polylactic acid is a polymer obtained by producing lactic acid using starch obtained from corn, potatoes, etc. as a raw material, and by chemical synthesis, and is excellent in mechanical properties, heat resistance, and transparency among aliphatic polyesters. Therefore, research and development for the purpose of developing various molded products such as films, sheets, tapes, fibers, ropes, non-woven fabrics, and containers have been actively conducted. However, compared with general-purpose resins typified by polyethylene terephthalate, it cannot be said that it has sufficient performance particularly in heat resistance, and technical studies for improving heat resistance are being conducted. For example, by removing a catalyst metal in a polymer by contacting a solid substance of polyhydroxycarboxylic acid with an acidic substance in the presence of an organic solvent, adding a polymerization catalyst deactivator, and devolatilizing under reduced pressure. A technique for obtaining a lactic acid-based polyester excellent in heat resistance and storage stability is disclosed (see Patent Documents 1 and 2).

  In the production of polylactic acid film, for example, a molten polymer extruded from a slit-shaped die is cast on a roll or a drum, and cooled and solidified. In order to adhere, a method of spraying air with an air knife to a polymer in a molten state, a method of applying an electric charge to make it adhere by an electrostatic force, a method of cooling cast through a water film, and the like are carried out.

  As an efficient and inexpensive method for obtaining a polylactic acid film, it is effective to increase the film extrusion rate at this time and increase the film forming speed by further increasing the rotation speed of the cooling drum. In the case of a polymer from which the catalytic metal has been removed, or a polymer that has lost its activity due to the deactivator, adhesion cannot be obtained even when an electric charge is applied, and air enters between the molten polymer and the drum, causing bubbles. Surface defects such as scratches occur, and the contact point to the drum fluctuates, resulting in insufficient cooling of the polymer and uneven physical properties in the width direction of the cast film, and high-speed take-up with insufficient cooling Therefore, there is a problem that the film width is reduced. Furthermore, due to the above problems, the stretchability is poor, and a uniform biaxially stretched film may not be obtained. As a countermeasure, when producing polylactic acid film, in order to increase the adhesion by electrostatic force, it is necessary to give a charge at a higher voltage compared to the normal method, so it is inefficient in energy, There were problems such as easy discharge around the base and drum. These problems become more conspicuous as the speed increases, and the technology for efficient production at high speed is still insufficient.

  Further, for example, in applications such as wrapping films for packaging, since polylactic acid is insufficient in flexibility as it is, various softening techniques mainly by adding a plasticizer have been studied.

  For example, a technique using lactic acid or a lactic acid oligomer as a plasticizer is disclosed (see Patent Documents 4 and 5). However, such polylactic acid containing a considerable amount of lactic acid or lactic acid oligomer has a problem that the thermal stability at the time of molding is low and it is easily hydrolyzed, so that the strength decreases in a relatively short period of time. In addition, a polyalkylene ether is a main component in a technology using a plasticizer such as a phthalate that is widely used for vinyl chloride (see Patent Document 3) and a copolymer of polylactic acid and polyalkylene ether. A technique related to a composition in which a plasticizer is mixed is disclosed (see Patent Document 6). However, when these plasticizers are added for softening, the plasticity is expressed immediately after the addition, but when the molded product is left in an air atmosphere, particularly in a high temperature atmosphere, time passes or in water, especially In a hot water atmosphere, there has been a problem that flexibility is remarkably lowered, such as extraction of a plasticizer, or transparency is lowered. Furthermore, a technique relating to a composition containing a polymer containing lactic acid as a main component and a block copolymer of polyalkylene ether and polylactic acid is disclosed (see Patent Document 7). However, this technology is a technology for the purpose of imparting antistatic properties, such as composition flexibility, volatilization and exudation of additives (plasticizer) when it is formed into a film as a molded product, extraction (bleed out), etc. The technology was insufficient from the viewpoint of suppression.

  In addition, as a flexible packaging film, a study on a wrap film has been conducted. For example, a liquid additive is blended into a resin mainly composed of a lactic acid-based aliphatic polyester, and physical properties such as a tensile elastic modulus of the film. Is disclosed in a specific range (see Patent Document 8). However, in such a method, since the suppression of volatilization, leaching, and extraction (bleed out) of the liquid additive is insufficient, it is difficult to maintain flexibility and the practicality is inferior.

As described above, while attempts have been made to add flexibility by adding a plasticizer to polylactic acid, volatilization, exudation, and extraction of the plasticizer when it is used as a film while still providing sufficient flexibility As for the film in which (bleed out) is suppressed, it has not been achieved yet.
JP 7-102053 A (paragraphs [0020] to [0025]) JP-A-8-301993 (paragraphs [0015] to [0019]) US Pat. No. 5,076,983 (column 4, line 37 to column 5, line 13) JP-A-6-306264 (paragraphs [0012] to [0022]) JP-A-4-335060 (paragraphs [0016] to [0026]) Japanese Patent Laid-Open No. 8-199052 (paragraphs [0004] to [0022]) JP-A-8-253665 (paragraphs [0005] to [0017]) JP 2000-26623 A (paragraphs [0005] to [0044])

  An object of the present invention is to provide a polyester resin composition and film mainly composed of a polylactic acid-based polymer, which is excellent in heat resistance, film moldability and productivity, which has not been achieved by the prior art, and also has flexibility. When used as a given film, in addition to excellent heat resistance, film formability, and productivity, it has sufficient flexibility and plasticizer volatilization, leaching, and extraction (bleed out). The object is to provide a suppressed polyester film. Furthermore, it is providing the polyester film suitable as a packaging film of the articles | goods represented by a wrap film, and foodstuffs.

In order to solve the above problems, the polyester resin composition of the present invention mainly has the following constitution. That is,
A polyester mainly composed of a polylactic acid-based polymer, containing an alkali metal element and / or an alkaline earth metal element, and having a melt specific resistance at 200 ° C. of 5 × 10 ^{6 to} 5 × 10 ⁹ Ω · It is a polyester resin composition characterized by being cm.

The film of the present invention mainly has the following configuration. That is,
It is the polyester film which consists of the said polyester resin composition.

The polyester resin composition of the present invention is a polyester mainly composed of a polylactic acid polymer, contains an alkali metal element and / or an alkaline earth metal element, and has a melt specific resistance of 5 × at 200 ° C. By using a polyester resin composition of 10 ^{6 to} 5 × 10 ⁹ Ω · cm, it is possible to provide a polyester resin composition having excellent heat resistance and excellent film moldability and productivity, which could not be achieved by conventional techniques. Is something that can be done. Furthermore, when used as a film with flexibility, in addition to being excellent in heat resistance, film moldability, and productivity, it has sufficient flexibility, and the plasticizer volatilizes, exudes, and extracts ( It is a polyester film in which bleeding out) is suppressed, and in particular, a polyester film useful as an article typified by a wrap film or a food packaging film can be obtained.

  Next, the polyester film of the present invention will be described.

The polyester resin composition of the present invention needs to have a melt specific resistance at 200 ° C. of 5 × 10 ^{6 to} 5 × 10 ⁹ Ω · cm.

When the melting specific resistance at 200 ° C. is less than 5 × 10 ⁶ Ω · cm, the applied charge does not stay in the film and tends to flow to the cooling drum side when cast on the cooling drum by the electrostatic application method. Adhesive strength under high speed conditions cannot be obtained. Furthermore, a portion where electric charge flows locally and a portion where current does not flow are generated on the film surface, a uniform adhesion state cannot be obtained in the width direction of the film, and air enters between the polymer and the drum in a streak-like manner. Disadvantages occur. On the other hand, when the melting specific resistance at 200 ° C. exceeds 5 × 10 ⁹ Ω · cm, the film is difficult to be charged and the adhesion force under high speed conditions cannot be obtained. In addition, when a higher voltage is applied, charges leak due to discharge to a base or a drum through which current easily flows, and adhesion cannot be obtained. In this case, the pressure on the film is increased due to the airflow generated in the rotating direction of the drum under high speed conditions, and the air enters between the molten polymer and the drum by exceeding the adhesion between the film and the drum. Such surface defects occur. By setting the melt specific resistance of the polyester resin composition of the present invention at 200 ° C. to 5 × 10 ^{6 to} 5 × 10 ⁹ Ω · cm, good adhesion under high-speed casting conditions is obtained, and a film having uniform physical properties is obtained. In addition, a wide film can be obtained. That is, it is possible to obtain a film with high quality and high productivity. Furthermore, it can be particularly suitably used when it is necessary to rapidly cool from a molten state to a low temperature, such as a polyester resin composition having a high crystallization rate or a composition having a low glass transition temperature. A preferable range of the melt specific resistance is 7 × 10 ⁶ to 1 × 10 ⁹ Ω · cm, more preferably 1 × 10 ^{7 to} 7 × 10 ⁸ Ω · cm, and further preferably 1 × 10 ^{7 to} 5 ×. 10 ⁸ Ω · cm. In the present invention, the melting specific resistance is a current flowing when a copper electrode having an area S is inserted in parallel in a molten polymer while maintaining a distance D, and a DC voltage V is applied between the electrodes at a polymer temperature of 200 ° C. The maximum value I is measured, and is a value obtained from Equation 1.

  Melting specific resistance (Ω · cm) = (V × S) / (I × D) (Formula 1).

  The method of setting the specific resistance of the polyester resin composition of the present invention to a specific range is not particularly limited, but is a method of adjusting the amount of metal in the polyester, amino group, sulfonic acid group, chlorine in the polyester. Examples thereof include a highly polar functional group such as a halogen-containing compound, a resin such as nylon having such a functional group, and a method of introducing or adjusting an additive. The polyester resin composition of the present invention needs to contain an alkali metal element and / or an alkaline earth metal element. When no alkali metal element and / or alkaline earth metal element is contained, it is necessary to introduce a large amount of the above-mentioned functional groups and metals when the melting specific resistance value falls within a specific range. It is easily affected by time and heat resistance is poor. Examples of metals other than alkali metals and alkaline earth metals include Al, Ti, Fe, Zn, Pb, Sn, Sb, Ge, etc., but the effect of lowering the melt specific resistance value is small and introduced in large quantities. Otherwise, the required melting specific resistance value cannot be obtained. Furthermore, the introduction of a large amount of these metals not only makes them susceptible to heat, but also reduces the degree of polymerization due to catalytic effects, promotes transesterification and decomposition, and increases the low molecular weight. Problems such as deterioration of mechanical properties of polyester and contamination due to volatilization of low molecular weight substances occur. That is, in the polyester resin composition of the present invention, the use of an alkali metal element and / or an alkaline earth metal element makes it possible to make the specific resistance value within a specific range with a very small amount of metal element in the polyester. Thus, a film excellent in heat resistance and productivity can be obtained.

  Examples of the alkali metal element and alkaline earth metal element to be contained in the polyester resin composition of the present invention include alkali metals such as Li, Na and K, alkaline earth metals such as Ca, simple metals of these metals or metal carbonates, Salts such as sulfates, phosphates, lactates and fatty acid salts, oxides, hydroxides, halides, etc. can be used, but the metal here is one that is dissolved in the polyester. Insoluble particles such as inorganic particles and aggregates, and foreign substances and aggregates generated by the reaction between metal and polyester are excluded because they have a small effect on the melt specific resistance.

  Among these metals, it is preferable to select those that are naturally decomposed or absorbed, those that are biodegradable, and those that are highly safe. Among them, calcium lactate, sodium lactate, potassium lactate, sodium stearoyl lactate, calcium stearoyl lactate and the like that have been confirmed to be safe as food additives and the like can be mentioned, but are not particularly limited. These metals may be used alone or in combination of two or more.

  The amount of alkali metal element and alkaline earth metal element in the polyester resin composition of the present invention is adjusted according to a desired melting specific resistance value. In the system which does not contain, it is preferable that it is 10 ppm or more and less than 500 ppm. This is because, depending on the amount of other metal elements, a desired melting specific resistance value may not be obtained if it is out of the above range. Furthermore, it is preferable that it is less than 500 ppm at the point which makes heat resistance favorable, More preferably, it is less than 300 ppm, More preferably, it is less than 200 ppm.

  As a method for setting the melt specific resistance of the polyester resin composition in a specific range, the method of adjusting the amount of alkali metal element or alkaline earth metal element in the polyester described above is most preferably used. As long as the effect of the present invention is not impaired, other metal elements or highly functional functional groups may be introduced or a resin having such a functional group may be blended. It is preferable to use a smaller amount of metal elements and functional groups. For example, when other metal elements are contained, the amount of other metal elements is preferably less than 300 ppm, more preferably less than 200 ppm, and still more preferably less than 100 ppm. The ratio of the alkali metal element and the alkaline earth metal element to the total amount of metal elements in the polyester is preferably 20% or more, more preferably 50% or more, and further preferably 80% or more.

  The method of blending the alkali metal element and the alkaline earth metal element in the polyester of the present invention may be blended and adjusted in advance during the synthesis of the polyester, or may be adjusted in addition during extrusion and film formation, In order to reduce the influence of metal elements on pyrolysis, it is preferable to shorten the time for receiving heat in a state containing metal, and to reduce the amount of polymer receiving heat in a state containing metal, for example, the minimum required for the synthesis of polyester A method of blending metals after synthesizing with a limited amount of catalyst metal, a method of blending the required amount of metals during extrusion film formation, etc. by reducing the catalyst metal by solvent washing and contact with an acidic solvent after polyester synthesis, A method of diluting and using a master raw material contained in a high concentration obtained by such a method is preferred.

  In the polyester resin composition of the present invention, a phosphorus compound may be blended for the purpose of adjusting to a desired melt specific resistance value and improving thermal stability within a range that does not impair the effects of the present invention. Examples of the phosphorus compound used include salts or esters such as phosphoric acid, phosphorous acid, and hypophosphorous acid, and also include compounds having two or more phosphorus elements in one molecule. Although not particularly limited, for example, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, etc. Alkyl esters, diesters and triesters may also be used. Among these phosphorus compounds, it is preferable to select those that are naturally decomposed or absorbed, those that are biodegradable, and those that are highly safe. Moreover, it is more preferable to select a low volatility and high heat resistance compound, for example, one having a molecular weight of 300 or more, in terms of easy control of the handling property and blending amount of the phosphorus compound. Further, when blended, it is preferable that the molar ratio (M / P) of the metal element (M) and the phosphorus element (P) is adjusted to 0.5 or more from the viewpoint of improving the effect of the present invention. Preferably it is 2 or more, more preferably 5 or more. The upper limit value of M / P is not particularly limited, but is determined by a desired melting specific resistance value and heat resistance.

  The polyester film of the present invention preferably has a film haze value of 0.2 to 5%. The film haze value is evaluated by the method described in the Examples, and refers to a value obtained by converting the actual measured value when the film thickness is 10 μm by proportional calculation. In particular, in the use of a wrapping film for packaging, especially a wrapping film for food packaging, if the film haze value is 0.2 to 5%, the contents can be easily distinguished, which is preferable. A preferable range of the film haze value is 0.2 to 3%, and a more preferable range is 0.2 to 1.5%. Also, in applications where a certain level of concealment is required, such as garbage bags and agricultural multi-films, or where light transmittance is low or absorption such as sunlight is preferred, coloring pigments may be used as necessary. It is good to add.

  The initial tensile modulus of elasticity of the film of the present invention at 23 ° C. is adjusted in accordance with the shape of the article to be packaged when it is used as a wrap film, for example, in terms of handling properties and process passability in the film forming process and processing process. It is preferably 0.1 to 2 GPa from the viewpoint of following deformation and obtaining good adhesion. A more preferable range of the initial tensile elastic modulus is 0.1 to 1.5 GPa, more preferably 0.15 to 1.2 GPa, and particularly preferably 0.2 to 1 GPa. Further, it is preferably 0.1 to 2 GPa in at least one direction, more preferably the initial tensile elastic modulus in the longitudinal direction of the film is in the above range, and further preferably in the above range in each direction.

  In addition, the film of the present invention has a weight change rate of 120% at 30 ° C. after 30 minutes of dry heat treatment, so that the flexibility is maintained even when the film is heated and used, and contamination by volatile components is caused. It is preferable in that it hardly occurs. More preferably, it is 1% or less, More preferably, it is 0.5% or less.

  The polyester in the present invention is mainly composed of the polylactic acid-based polymer (A) and mainly contains L-lactic acid and / or D-lactic acid, and the component derived from lactic acid in the polyester is 50% by weight or more. Preferably 70% by weight or more. Such polyester may be, for example, copolymerized polylactic acid obtained by copolymerizing other monomer components having ester forming ability in addition to homopolylactic acid composed of L-lactic acid and / or 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 derivatives thereof, 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. In addition, it is preferable to select the component which has biodegradability as a copolymerization component of the polylactic acid-type polymer used in this invention. The weight average molecular weight of the polylactic acid polymer (A) used in the present invention is usually at least 50,000, preferably 80,000 to 300,000, and more preferably 100,000 to 200,000. When the average molecular weight is in such a range, the strength physical properties in the case of a film can be made excellent.

  As the polyester in the present invention, the homopolylactic acid, a copolymer of lactic acid and other components, a mixture thereof, a mixture with other thermoplastic resins, or a composition in which a plasticizer or a lubricant is added to these, etc. Although it can be used, it provides good flexibility and suppresses volatilization, leaching, and extraction (bleed out) of oligomer components and plasticizers, and the above-described polylactic acid polymer (A) and in one molecule It is more preferable to use a polyester having at least one polylactic acid segment having a molecular weight of 1,500 or more and a plasticizer (B) having a polyether-based and / or polyester-based segment.

  Furthermore, the polylactic acid segment of the plasticizer (B) is incorporated into a crystal formed from the polylactic acid polymer (A) as a base material, thereby causing the plasticizer molecule to bind to the base material. Since this action can sufficiently suppress the volatilization, exudation, and extraction (bleed out) of the plasticizer, the polylactic acid polymer used as the base material preferably has crystallinity. The polylactic acid-based polymer has crystallinity when the polylactic acid-based polymer is sufficiently crystallized under heating and then subjected to DSC (Differential Scanning Calorimetry) measurement in an appropriate temperature range. It means that the heat of crystal melting derived from the polylactic acid component is observed. For example, when uniform homopolylactic acid is used as the polylactic acid polymer (A), homopolylactic acid having an optical purity of 70% or more may be used. Alternatively, depending on the purpose of use, two or more types of homopolylactic acid having different optical purities may be used in combination for the purpose of imparting or improving a required function. For example, homopolylactic acid having crystallinity and amorphous These homopolylactic acids can also be used in combination. 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. In general, homopolylactic acid has a higher melting point as the optical purity is higher. For example, poly L-lactic acid having an optical purity of 98% or higher has a melting point of about 170 ° C., but has a high heat resistance when formed into a polylactic acid-based molded product. When it is desired to impart the properties, it is preferable that at least one of the polylactic acid polymers used contains polylactic acid having an optical purity of 95% or more.

  Further, the plasticizer (B) used in the present invention is such that the plasticizer efficiency of the plasticizer is such that the weight ratio of the polylactic acid segment component of the plasticizer is less than 50% by weight of the entire plasticizer (B). Since it is relatively high and desired flexibility can be imparted with a smaller amount of addition, it is preferable. Furthermore, the molecular weight of the polylactic acid segment in one molecule of the plasticizer should be 1500 or more and less than 10,000, so that the plasticization efficiency and the polylactic acid segment can be incorporated more into the base material crystal, and the plasticizer volatilizes and exudes. From the viewpoint of suppressing extraction (bleed out). More preferably, it is 2000 or more and less than 6000.

  The plasticizer (B) has a polylactic acid segment containing 95% by weight or more of the component derived from L-lactic acid or 95% by weight or more of the component derived from D-lactic acid. Volatilization, exudation, and extraction (bleed out) are particularly suppressed, which is preferable.

  In the polyester film of the present invention, the addition amount of the plasticizer (B) may be appropriately determined in accordance with characteristics such as flexibility and strength required for a desired application, but the polylactic acid segment component of the plasticizer is excluded. The weight ratio of the plasticizing component is preferably 5% by weight or more and 30% by weight or less of the entire composition. In this case, a composition having an excellent balance between mechanical properties such as flexibility and strength properties can be obtained.

  In addition, the plasticizer (B) used in the present invention has a polyether-based and / or polyester-based segment. Flexibility can be imparted to polylactic acid by introducing polyether-based and / or polyester-based segments into the plasticizer. Among polyether series, it is preferable to have a segment made of polyalkylene ether, and more preferably to have a segment made of polyethylene glycol. When the plasticizer (B) is a polyalkylene ether such as polyethylene glycol, polypropylene glycol or polyethylene glycol / polypropylene glycol copolymer, especially polyethylene glycol, the plasticizer has a high affinity with the polylactic acid polymer (A). A polylactic acid polymer composition having an excellent plasticizing efficiency and having a desired flexibility can be obtained by adding a small amount of plasticizer. In addition, when the plasticizer (B) 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 during molding or the like. It is preferable to use an antioxidant such as a hindered phenol and a hindered amine, which will be described later, and a thermal stabilizer such as a phosphorus as long as the effects of the above are not impaired.

  In addition, it is preferable to select the component which has biodegradability as components other than the polylactic acid segment of the plasticizer (B) used in this invention.

  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 generate lactide, which is a cyclic dimer, and then ring-opening polymerization is performed. 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, the cast drum becomes dirty and the smoothness of the film surface decreases. Therefore, the content of the cyclic dimer contained in the polymer at the stage of molding or before melt film formation is 0.3 weight. % 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 addition, you may contain components other than the above-mentioned specific plasticizer in the polyester which has the polylactic acid-type polymer (A) of this invention as a main body 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, Particles such as polystyrene, 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.

  Furthermore, the polyester mainly composed of the polylactic acid-based polymer (A) of the present invention includes polylactic acid as long as the effects of the present invention are not impaired for the purpose of reducing melt viscosity or improving biodegradability. Aliphatic polyesters other than the polymer 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 polyester of the present invention has a polylactic acid polymer (A) and at least one polylactic acid segment having a molecular weight of 1,500 or more in one molecule, and a plastic having a polyether and / or polyester segment. When components other than the agent (B) are contained, it is preferable to select components having biodegradability.

  The plasticizer (B) used in the present invention has, for example, a polymer obtained by polymerizing a polylactic acid oligomer having a molecular weight of 1,500 or more in advance by a conventional method such as a lactide ring-opening method or a lactic acid condensation polymerization method. It can be obtained by reacting a suitable amount with a compound having a polyether-based and / or polyester-based segment which is a main component of a plasticizer. Ring-opening polymerization of lactide using a compound which is a main component of a plasticizer as a polymerization initiator May be added thereto, or may be added thereto by dehydration condensation polymerization of lactic acid using a compound which is a main component of the plasticizer as a polymerization initiator. In addition, a polyfunctional oligomer such as a dicarboxylic acid anhydride compound or a diisocyanate compound is chained by a treatment such as heat kneading in the presence of a polylactic acid oligomer having a molecular weight of 1,500 or more and a compound comprising the main component of the plasticizer. Both may be chemically bonded by acting as a linking agent.

  Next, a more specific example of the plasticizer (B) having one or more polylactic acid segments having a molecular weight of 1,500 or more in one molecule and having a polyether-based and / or polyester-based segment will be described.

  Prepare polyethylene glycol (PEG) having hydroxyl ends at both ends. The average molecular weight (MPEG) of polyethylene glycol (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 commercially available products. In a system in which lactide wA parts by weight are added to parts by weight of polyethylene glycol (PEG) wB parts having hydroxyl ends at both ends, lactide is ring-opening addition polymerized at both ends of hydroxyl groups of PEG and sufficiently reacted. A PLA (A) -PEG (B) -PLA (A) type block copolymer can be obtained. 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 weight ratio with respect to the whole plasticizer of a polylactic acid segment component can be calculated | required substantially as 100xwA / (wA + wB)%. Furthermore, the weight ratio of the plasticizing component excluding the polylactic acid segment component to the entire plasticizer can be substantially calculated as 100 × wB / (wA + wB)%. The numerical values exemplified above are actually average values, and the molecular weight of the generated plasticizer and the segment length of the polylactic acid portion have a certain distribution. A compound containing a polymer as a main component can be obtained.

  When the plasticizer contains a large amount of unreacted PEG or unreacted product such as PEG having a molecular weight of less than 1,500 at the terminal polylactic acid segment, lactide oligomers, or impurities, for example, This is preferably removed by a 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.

  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, using a deuterated chloroform solution of a plasticizer, based on a chart obtained by 1H-NMR measurement, (1/2) × (IPLA × 72) / (IPEG × 44/4) × MPEG is calculated. 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 condition that the reaction rate of lactide at the time of plasticizer synthesis is sufficiently high and almost all lactide is subjected to ring-opening addition to the PEG end, in many cases, based on the chart obtained by 1H-NMR measurement This method is preferred.

  In addition, as a method for separating the plasticizer (B) used for the evaluation of the polylactic acid segment molecular weight and the like from the polyester in the present invention, for example, after uniformly dissolving the polyester in a suitable good solvent such as chloroform, The precipitate containing mainly the polylactic acid polymer (A) is removed by dropping into a suitable poor solvent such as a water / methanol mixed solution, and the filtrate is evaporated to obtain a separated plasticizer. Examples thereof include, but are not limited to, a precipitation method, and an appropriate method may be selected or combined depending on the plasticizer or polylactic acid polymer used.

  For example, a PLA (A) -PEG (B) -PLA (A) type block copolymer having one or more polylactic acid segments having a molecular weight of 1,500 or more in one molecule is obtained by the above-described method. When used as the agent (B), it is sufficient to provide a molded article having sufficient flexibility and suppressing the volatilization, leaching and extraction (bleed out) of the plasticizer, which could not be achieved by the prior art. An effect can be obtained.

  Moreover, as a method of adding the plasticizer (B) described above to the polylactic acid polymer (A), the plasticizer is added and melt kneaded in a desired weight ratio in the molten state of the polylactic acid polymer. However, from the viewpoint of increasing the degree of polymerization of the polylactic acid-based polymer 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 polymer. Examples of the addition / melt kneading of the above-described polylactic acid polymer and plasticizer include, for example, a method of adding a plasticizer to a molten polylactic acid polymer immediately after the completion of the polycondensation reaction, stirring and melt kneading, and polylactic acid A method in which a plasticizer is added and mixed to a polymer chip and then melt-kneaded in a reactor or an extruder, etc., a method in which a plasticizer is continuously added to a polylactic acid polymer with an extruder, and melt-kneaded. The concentration of the polylactic acid polymer master chip and the polylactic acid polymer homochip mixed can be mixed and melt-kneaded with an extruder or the like.

  The thickness of the polyester film of the present invention may be appropriately adjusted according to the use, but is preferably 5 to 500 μm, flexibility when used as a packaging film such as a wrap film or a bag, handleability, From the viewpoint of strength, it is more preferably 5 to 100 μm, further preferably 7 to 50 μm, and particularly preferably 7 to 30 μm.

  The polyester film of the present invention is an article represented by a bag or the like, such as heat sealability, gas barrier properties such as water vapor, oxygen, carbon dioxide gas, releasability, printability, etc., as long as the effects of the present invention are not impaired. Further, properties required as packaging materials for foods 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 polyester film of this invention is demonstrated.

  The polyester film of the present invention can be obtained by an existing method for producing a stretched film such as an inflation method, a sequential biaxial stretching method, or a simultaneous biaxial stretching method. Among these, a sequential biaxial stretching method and a simultaneous biaxial stretching method that can effectively utilize a casting method in which an electric charge is applied and the adhesion to the cooling drum is enhanced by electrostatic force are preferable. In any case, in order to reduce the water content and lactide content of the polylactic acid polymer used, it is vacuum dried at 90 ° C. to 130 ° C., the degree of vacuum is set to a high vacuum of 10 Torr or less, and the drying time is 6 hours or more. It is preferable that 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 temperature of an extruder, polymer piping, base, etc. is 200. ° C or lower is preferable, 190 ° C or lower is more preferable, and 180 ° C or lower is more preferable. The residence time from when the polylactic acid polymer 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 further preferably 5 minutes or less. It is more preferable. In addition, when the plasticizer (B) is added to the polylactic acid polymer (A), for example, a polylactic acid polymer master chip containing a high concentration of plasticizer and a polylactic acid polymer homochip are mixed. The blended chips may be subjected to melt-kneading by applying them to an extrusion system of a film forming machine such as an extruder. However, in order to minimize the thermal deterioration of the composition, a raw material that has been dried under vacuum is used. A method in which a plasticizer in a liquid state, such as heating as needed, is continuously added to a polylactic acid polymer melted in the extruder by using an extruder, etc., is added continuously, and melt-kneaded. . 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 low molecular weight components such as moisture and oligomers generated during melting.

The extruded sheet-like melt is brought into close contact with the casting drum and solidified by cooling to obtain an unstretched film. As a method for closely contacting the casting drum, a casting method in which an electric charge is applied and the close contact with the cooling drum is enhanced by electrostatic force is most preferably used under high speed conditions. Apply a predetermined voltage to the wire, tape, or needle electrode, place it at any location between the die and the cooling drum, and apply a charge to the entire width and / or edge of the sheet-like melt. The polymer discharged from the die is grounded and brought into close contact with the cooling drum in a shorter time. The preferred installation location of the electrode is not particularly limited, but the case where the base is the top of the drum and a wire electrode is used as an example, the distance between the base and the drum surface is 10 to 50 mm, and no charge is applied. When the drum is rotated and cast, the sheet is installed at a position on the line where the sheet comes into contact with the drum, and the distance from the drum surface is set at a position of 10 to 30 mm so as to be parallel to the drum surface. The preferred applied voltage needs to be changed depending on the melt specific resistance value of the polymer and the desired adhesion state, film thickness, electrode shape, applied length and width, distance between the electrode and the drum, etc. For example, when a sheet having a width of 300 to 500 mm is used for casting, it is 5 to 12 KV. The wire used is preferably 0.1 to 0.5 mm in diameter and made of tungsten. The casting drum is preferably a mirror drum subjected to hard chrome plating.
In addition, for the purpose of increasing the adhesion force, reducing the film width, and suppressing the fluctuation of the width, a method of blowing air using an air knife or a method of casting on the drum surface via a water film can be used in combination. In particular, it is preferable to use a method of casting on the drum surface via a water film in terms of suppressing the intrusion of the airflow by the surface tension of water. For the same purpose, a method of changing the viscosity of the polyester used or setting the temperature of the cooling drum higher than the glass transition temperature of the polyester within a range that does not hinder the effects of the present invention and increasing the adhesion force. Can be used together. The unstretched film obtained by such a method can be obtained by continuously stretching in at least one direction. Further, when the sequential biaxial stretching method is used, for example, the unstretched film is stretched in the longitudinal direction by roll stretching using the peripheral speed difference of the heated roll, and then the first-stage stretching direction in the tenter having a continuous clip. Stretching in an orthogonal direction can be performed, and heat treatment can be performed in the tenter and / or after winding after the stretching.

  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 plasticizer (B) into this crystal, volatilization and leaching of the plasticizer, Since extraction (bleed out) can be further suppressed, it is preferable. 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 is preferably performed at a higher temperature in the range of the glass transition temperature of the polyester to the melting point from the viewpoint of film strength and dimensional stability. Further, it is more preferable to perform heat treatment for longer than 100 ° C. for 10 seconds or longer for the purpose of reducing low molecular weight components such as oligomer components in the film.

  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 polyester resin composition and film of the present invention have excellent heat resistance, excellent film moldability and productivity, and when used as a film with flexibility, heat resistance, film moldability and production. In addition to being excellent in properties, it has sufficient flexibility, transparency and strength properties, and can be used in a wider field than ever. 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, nursery pots, flower pots and the like.

  The polyester resin composition and film of the present invention are high-quality resin compositions and films having excellent heat resistance and excellent film moldability and productivity. Furthermore, when used as a film with flexibility, in addition to excellent heat resistance, film formability, and productivity, it also has practically sufficient flexibility, transparency, and strength properties. At times, there is virtually no volatilization, exudation, or extraction (bleed out) of the plasticizer, so that the flexibility and transparency can maintain the performance at the start of use for a long period of use. In addition, when a biodegradable plasticizer is contained, a packaging wrap film that 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 is possible to obtain a film that exhibits the original performance without deterioration even after a long period of time after production. In addition, to obtain a film having stable flexibility and transparency even after various dry heat processing and after processing in a high temperature atmosphere in various post-processing steps of the molded product performed after film forming and the like. Can do.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by a following example. In addition, the physical property in an Example is the value measured with the following method.

(1) Melt specific resistance [Ω · cm]
120 g of the polyester resin composition is put into a 50 mmφ test tube, melted at 200 ° C. in a nitrogen atmosphere, and a 3 cm × 5 cm (area S) copper electrode is inserted in parallel with a distance D of 1 cm being opposed. . Next, the maximum value I of the current that flows when a DC voltage V of 5000 V was applied between the electrodes was measured and obtained from Equation 1. This was measured three times in total to obtain an average value, which was taken as the melt specific resistance.

Melting specific resistance (Ω · cm) = (V × S) / (I × D) (Formula 1)
The same measurement was performed when the sample was in the form of a film.

(2) Metal element and phosphorus element amounts [ppm]
The sample was heated and melted at 200 ° C., a circular disk was prepared, X-ray fluorescence analysis was performed, and the amount of metal element and the amount of phosphorus element were determined using a calibration curve obtained from a sample in which the amount of each metal element was changed in advance. .

  If insoluble matter such as particles is included, dissolve the polyester resin composition in chloroform and perform centrifugation, then remove the insoluble matter such as particles by filtration to precipitate the polymer in the solution. Thereafter, fluorescent X-ray analysis was performed to determine the amount of metal element.

  At this time, the total amount of elements of Li, Na, K, Ca, Sn, and Sb was defined as the total amount of metal elements. However, the total amount was determined by excluding metal elements of less than 5 ppm.

  The amount of phosphorus element was also determined by the same method.

  The same measurement was performed when the sample was in the form of a film.

(3) High-speed castability An unstretched film was obtained by casting at an applied voltage of 8 KV using a tungsten wire electrode on a casting drum having a temperature of 20 ° C. and a diameter of 600 mm using a base having a width of 300 mm. At this time, while adjusting the extrusion amount so that the thickness of the unstretched film became constant at 100 μm, the rotational speed of the casting drum was increased, and the entrainment of air due to the decrease in the adhesion was observed. At this time, the speed at which the entrained bubble traces did not disappear even when the position of the electrode was adjusted was evaluated as the upper limit of the casting speed. A casting speed of 20 m / min or more is excellent in practicality. The bubble scar is a surface defect in which air is entrained between the surface of the casting drum and the film and shows a convex shape on the surface side of the film (surface side not in contact with the drum). This defect occurs when the pressure on the film increases due to the airflow generated in the rotation direction of the drum as the casting speed increases and exceeds the adhesion between the film and the drum.

(4) Haze value of film A film sample was cut into a length of 40 mm and a width 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 measured 5 times in total using a haze meter HGM-2DP (Suga Test Instruments Co., Ltd.) in an atmosphere of 23 ° C. according to JIS K7136, and the average value was taken as the film haze value.

  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.

(5) Initial tensile modulus of elasticity of film [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 type (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. The average value was obtained and used as the initial tensile elastic modulus.

(6) Rate of weight change after dry heat treatment [%]
A biaxially stretched film sample conditioned for 24 hours under an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH was measured in advance, and the weight before treatment was measured for 30 minutes in a 120 ° C. hot air oven. After adjusting the humidity under the conditions, the weight was measured. The weight change rate was calculated as the ratio of the weight change (decrease) before and after treatment to the weight before treatment.

(7) Heat resistance After immersing for 30 minutes in a 180 ° C. silicone oil bath in a test tube containing 10 g of a film sample, the test tube was cooled and solidified with 25 ° C. water to obtain a heat-treated sample. . After adding 10 ml of o-chlorophenol to 0.3 g of this sample and dissolving at 100 ° C. for 30 minutes, the viscosity at a measurement temperature of 25 ° C. was measured using an Ostwald type viscosity tube having a flow time of o-chlorophenol of 100 seconds. The sample before and after heat treatment was measured, and the ratio of the amount of change to the viscosity before heat treatment was determined as the rate of change. Similarly, the evaluation was performed at 190, 200, 210, and 220 ° C., and the temperature at which the change rate was maintained below 5% was defined as the heat resistant temperature. In addition, the thing whose change rate exceeded 5% at 180 degreeC was made into heat-resistant temperature less than 180 degreeC.

  The polylactic acid polymer and plasticizer used in this example were obtained as follows.

<Polylactic acid polymer (P1)>
0.1 parts by weight of octylate and 0.1 parts by weight of lauryl alcohol are mixed with 100 parts by weight of L-lactide and polymerized in a reaction vessel equipped with a stirrer at 190 ° C. for 15 minutes in a nitrogen atmosphere. After chipping with a shaft kneading extruder, solid-phase polymerization was performed in a nitrogen atmosphere at 140 ° C. for 3 hours to obtain a polylactic acid polymer P1. When DSC measurement was performed on P1, P1 had crystallinity, the crystallization temperature was 128 ° C., and the melting point was 171 ° C.

<Polylactic acid polymer (P2)>
P1 polymer was added to a solution prepared by adjusting the volume ratio of 0.5N hydrochloric acid and ethanol to 1: 1 so that the solid content concentration would be 10% by weight, followed by stirring at 35 ° C. for 4 hours. Went. Next, after separating the solid content, drying was performed with heated nitrogen at 80 ° C. to obtain a polylactic acid polymer P2.

<Polylactic acid polymer (P3)>
0.08 part by weight of octylate and 0.1 part by weight of lauryl alcohol are mixed with 68 parts by weight of L-lactide and 32 parts by weight of DL-lactide having a purity of 96%, and a nitrogen atmosphere in a reaction vessel equipped with a stirrer. Polymerization was carried out at 190 ° C. for 3 hours, and chips were formed using a biaxial kneading extruder. Next, a treatment was performed in the same manner as P2 except that this chip was used to obtain a polylactic acid polymer P3. When DSC measurement was performed on P3, the crystallinity was not exhibited, and the crystallization temperature and the melting point were not observed.

<Plasticizer (S1)>
0.07 parts by weight of tin octylate is mixed with 65 parts by weight of poly (1,3-butanediol adipate) having an average molecular weight of 8,000 and 35 parts by weight of L-lactide, and nitrogen is added in a reaction vessel equipped with a stirrer. Polymerization was carried out in an atmosphere at 190 ° C. for 60 minutes to obtain a block copolymer of poly (1,3-butanediol adipate) and polylactic acid having a polylactic acid segment having an average molecular weight of 2,150. This copolymer was dissolved in chloroform and stirred, and then poured into 20 times volume of diethyl ether of chloroform to obtain a precipitate. The precipitate was filtered and separated, and dried at room temperature under a high vacuum of 5 torr for 24 hours to obtain a plasticizer (S1).

<Plasticizer (S2)>
0.072 parts by weight of tin octylate is mixed with 72 parts by weight of polyethylene glycol having an average molecular weight of 12,000 and 28 parts by weight of L-lactide, and polymerized in a reaction vessel equipped with a stirrer at 190 ° C. for 60 minutes in a nitrogen atmosphere. Thus, a block copolymer of polyethylene glycol and polylactic acid having a polylactic acid segment having an average molecular weight of 2,330 was obtained. This copolymer was dissolved in chloroform and stirred, and then poured into 20 times volume of diethyl ether of chloroform to obtain a precipitate. This precipitate was filtered and separated, and dried at room temperature under a high vacuum of 5 torr for 24 hours to obtain a plasticizer (S2).

<Plasticizer (S3)>
A block copolymer of polyethylene glycol and polylactic acid having a polylactic acid segment having an average molecular weight of 2,570 was obtained in the same manner as plasticizer S2. This copolymer was dissolved in chloroform and stirred, and then poured into 20 times volume of diethyl ether of chloroform to obtain a precipitate. The precipitate was filtered and separated, and dried at room temperature under a high vacuum of 5 torr for 24 hours to obtain a plasticizer (S3).

(Example 1)
100 parts by weight of a polylactic acid polymer (P1) was dried under reduced pressure at 120 ° C. for 5 hours under a vacuum of 5 torr, and then subjected to a twin-screw kneading extruder with a cylinder temperature of 190 ° C., and 0.04 part by weight of calcium acetate was melted into a molten polymer. The resulting mixture was kneaded and homogenized to form chips. This was dried under reduced pressure at 120 ° C. for 5 hours under a vacuum of 5 torr, then supplied to a single-screw extruder having a screw diameter of 40 mm, melt extruded from the die slit part at an extruder cylinder temperature of 200 ° C., and a T die die temperature of 200 ° C., A wire electrode was used on a cooling drum having a diameter of 600 mm cooled to 25 ° C., and cast by electrostatic application at an applied voltage of 8 KV to prepare an unstretched film. Continuously stretched by a factor of 3.2 using a peripheral speed difference between a heating roll and a cooling roll at 85 ° C., and then the obtained uniaxially stretched film was guided into a stenter and held with a clip, and heated at a temperature of 75 ° C. While being stretched 3.0 times in the transverse direction and fixed in the width direction, heat treatment was performed at 140 ° C. for 20 seconds to obtain a polyester film having a thickness of 12 μm. The evaluation results of the obtained film are shown in Table 1. The melt specific resistance of this film was measured and found to be 1.1 × 10 ⁹ Ω · cm. Moreover, the amount of metal elements was Ca: 72 ppm, Sn: 280 ppm, and the total amount of metal elements was 352 ppm. Separately, as a result of a high-speed castability test, the limit speed was 33 m / min.

（比較例１）
ポリ乳酸系重合体（Ｐ１）１００重量部を用い、酢酸カルシウムの代わりに三酸化二アンチモン０．０４重量部を添加すること以外は実施例１と同様にして、厚さ１２μｍの二軸延伸ポリエステルフィルムを得た。得られたフィルムの評価結果を表１に示す。このフィルムの溶融比抵抗を測定した結果、１．５×１０⁹Ω・ｃｍであった。金属元素量およびリン元素量は、Ｓｎ：２８０ｐｐｍ、Ｓｂ：２５３ｐｐｍであり、金属元素の総量は、５３３ｐｐｍであった。また、別に、高速キャスト性のテストを行った結果、限界速度は２８ｍ／分であった。

(Comparative Example 1)
Biaxially stretched polyester having a thickness of 12 μm in the same manner as in Example 1 except that 100 parts by weight of the polylactic acid polymer (P1) is used and 0.04 part by weight of antimony trioxide is added instead of calcium acetate. A film was obtained. The evaluation results of the obtained film are shown in Table 1. As a result of measuring the melt specific resistance of this film, it was 1.5 × 10 ⁹ Ω · cm. The amount of metal element and the amount of phosphorus element were Sn: 280 ppm, Sb: 253 ppm, and the total amount of metal elements was 533 ppm. Separately, as a result of a high-speed castability test, the limit speed was 28 m / min.

(Comparative Example 2)
A biaxial shaft having a thickness of 12 μm was used in the same manner as in Example 1 except that 100 parts by weight of the polylactic acid polymer (P2) was used as a raw material and 0.01 parts by weight of calcium stearate was added instead of calcium acetate. A stretched polyester film was obtained. The evaluation results of the obtained film are shown in Table 1. As a result of measuring the melt specific resistance of this film, it was 6 × 10 ⁹ Ω · cm. The amount of metal element and the amount of phosphorus element were Ca: 8 ppm, Sn: 10 ppm, and the total amount of metal elements was 18 ppm. Separately, as a result of a high-speed castability test, the limit speed was 15 m / min.

(Example 2)
55 parts by weight of a polylactic acid polymer (P1) and 45 parts by weight of a plasticizer (S1) were dried under reduced pressure under a vacuum of 5 torr at 110 ° C. for 5 hours, and then subjected to a twin-screw kneading extruder having a cylinder temperature of 190 ° C. 0.03 parts by weight of an 80% aqueous solution of potassium was added into the molten polymer, kneaded while being reduced in pressure by 20 torr from the vent hole of the extruder, and then homogenized to form chips. This was dried under reduced pressure under a vacuum of 5 torr at 120 ° C. for 5 hours, then supplied to a single-screw extruder with a screw diameter of 40 mm, melt extruded from the slit portion of the die at an extruder cylinder temperature of 200 ° C. and a T die die temperature of 200 ° C., A wire electrode was used on a cooling drum having a diameter of 600 mm cooled to 5 ° C., and was applied by electrostatic application at an applied voltage of 8 KV to produce an unstretched film. Using a circumferential speed difference between a heating roll and a cooling roll at 65 ° C., the film was stretched 3.1 times, and the resulting uniaxially stretched film was guided into a stenter and held with a clip, and heated at a temperature of 65 ° C. While being stretched 3.1 times in the transverse direction and fixed in the width direction, heat treatment was performed at 140 ° C. for 20 seconds to obtain a polyester film having a thickness of 12 μm. The evaluation results of the obtained film are shown in Table 1. As a result of measuring the melt specific resistance of this film, it was 7.5 × 10 ⁸ Ω · cm. Moreover, the amount of metal elements was K: 83 ppm, Sn: 208 ppm, and the total amount of metal elements was 291 ppm. Separately, as a result of a high-speed castability test, the limit speed was 37 m / min.

(Example 3)
Using 70 parts by weight of a polylactic acid polymer (P2) and 30 parts by weight of a plasticizer (S2), 0.07 parts by weight of sodium glycolate is added instead of an 80% aqueous solution of potassium acetate, and stretching in the longitudinal and width directions A biaxially stretched film having a thickness of 15 μm was obtained in the same manner as in Example 2 except that the temperature was 60 ° C. The evaluation results of the obtained film are shown in Table 1. As a result of measuring the melt specific resistance of this film, it was 9 × 10 ⁷ Ω · cm. Moreover, the amount of metal elements was Na: 146 ppm, Sn: 30 ppm, and the total amount of metal elements was 176 ppm. In addition, as a result of performing a high-speed castability test separately, the limit speed was 46 m / min.

Example 4
Using 65 parts by weight of a polylactic acid polymer (P2) and 35 parts by weight of a plasticizer (S3), 0.05 parts by weight of calcium lactate monohydrate is added instead of an 80% aqueous solution of potassium acetate, and the longitudinal direction and width A biaxially stretched film having a thickness of 12 μm was obtained in the same manner as in Example 2 except that the direction stretching temperature was 60 ° C. The evaluation results of the obtained film are shown in Table 1. As a result of measuring the melt specific resistance of this film, it was 3.5 × 10 ⁸ Ω · cm. Moreover, the amount of metal elements was Ca: 86 ppm, Sn: 39 ppm, and the total amount of metal elements was 125 ppm. Separately, as a result of a high-speed castability test, the limit speed was 43 m / min.

(Example 5)
30 parts by weight of a polylactic acid polymer (P1), 40 parts by weight of a polylactic acid polymer (P3) and 30 parts by weight of a plasticizer (S3) are used, and 0.22 weight by weight of sodium stearoyl lactate instead of an 80% aqueous solution of potassium acetate. A biaxially stretched film having a thickness of 12 μm was obtained in the same manner as in Example 2 except that a part was added and the stretching temperature in the longitudinal direction and the width direction was set to 60 ° C. The evaluation results of the obtained film are shown in Table 1. As a result of measuring the melt specific resistance of this film, it was 1.6 × 10 ⁸ Ω · cm. Moreover, the amount of metal elements was Na: 103 ppm, Sn: 125 ppm, and the total amount of metal elements was 228 ppm. Separately, as a result of a high-speed castability test, the limit speed was 45 m / min.

(Example 6)
30 parts by weight of a polylactic acid polymer (P1), 40 parts by weight of a polylactic acid polymer (P3) and 30 parts by weight of a plasticizer (S3) are used, and 0.22 weight by weight of sodium stearoyl lactate instead of an 80% aqueous solution of potassium acetate. A homogenized chip was obtained in the same manner as in Example 2 except that the part was added. This chip was dried under reduced pressure at 120 ° C. for 5 hours under a vacuum of 5 torr, and then mixed with 0.1 part by weight of a phosphorus resin modifier “ADK STAB AX-71” manufactured by Asahi Denka Kogyo Co., Ltd. and supplied to the extruder. A biaxially stretched film having a thickness of 12 μm was obtained in the same manner as in Example 5 except that. The evaluation results of the obtained film are shown in Table 1. The melt specific resistance of this film was measured and found to be 5.2 × 10 ⁸ Ω · cm. Moreover, the amount of metal elements was Na: 102 ppm, Sn: 124 ppm, and the total amount of metal elements was 226 ppm. The amount of phosphorus element was 62 ppm. Separately, as a result of a high-speed castability test, the critical speed was 41 m / min.

(Example 7)
Using 50 parts by weight of a polylactic acid polymer (P2), 20 parts by weight of a polylactic acid polymer (P3), and 30 parts by weight of a plasticizer (S2), 0.1 weight of sodium glycolate instead of an 80% aqueous solution of potassium acetate A biaxially stretched film having a thickness of 12 μm was added in the same manner as in Example 2 except that 0.06 part by weight of calcium lactate monohydrate was added and the stretching temperature in the longitudinal direction and the width direction was set to 60 ° C. Obtained. The evaluation results of the obtained film are shown in Table 1. As a result of measuring the melt specific resistance of this film, it was 8 × 10 ⁶ Ω · cm. Moreover, the amount of metal elements was Na: 220 ppm, Ca: 105 ppm, Sn: 30 ppm, and the total amount of metal elements was 355 ppm. Separately, as a result of a high-speed castability test, the limit speed was 36 m / min.

(Comparative Example 3)
Except that 55 parts by weight of the polylactic acid polymer (P1) and 45 parts by weight of the plasticizer (S1) were used, and the addition amount of the 80% potassium acetate aqueous solution was 0.23 parts by weight, the same as in Example 2. A biaxially stretched film having a thickness of 12 μm was obtained. The evaluation results of the obtained film are shown in Table 1. The melt specific resistance of this film was measured and found to be 4 × 10 ⁶ Ω · cm. Moreover, the amount of metal elements was K: 610 ppm, Sn: 205 ppm, and the total amount of metal elements was 815 ppm. Separately, as a result of a high-speed castability test, the limit speed was 12 m / min.

  The present invention is not limited to wrapping film for packaging, and is effective in the field of other films that can be applied to electrostatic application cast technology and its application in particular, and includes packaging materials, agricultural films, automotive coating film protection sheets, garbage bags, compost Although the present invention can be applied to films for industrial materials such as bags and films for industrial materials in which various soft vinyl chlorides are used, the application range is not limited thereto.

Claims (12)

A polyester mainly composed of a polylactic acid polymer (A), which contains an alkali metal element and / or an alkaline earth metal element, and has a melt specific resistance of 5 × 10 ^{6 to} 5 × 10 at 200 ° C. A polyester resin composition characterized by having ⁹ Ω · cm. 2. The polyester resin composition according to claim 1, wherein the total amount of metal elements in the composition is less than 500 ppm. A polyester film comprising the polyester resin composition according to claim 1. The polyester film according to claim 3, wherein the film haze value is 0.2 to 5%. The polyester film according to claim 3 or 4, wherein an initial tensile elastic modulus at 23 ° C is 0.1 to 2 GPa. The polyester film according to any one of claims 3 to 5, wherein a rate of change in weight when the film is treated in a hot air oven at 120 ° C for 30 minutes is 2% or less. The composition has a crystalline polylactic acid polymer (A), one or more polylactic acid segments having a molecular weight of 1,500 or more in one molecule, and a polyether-based and / or polyester-based segment. It consists of a plasticizer (B), The polyester film in any one of Claims 3-6 characterized by the above-mentioned. The polyester film according to claim 7, wherein the weight ratio of the polylactic acid segment component of the plasticizer (B) is less than 50% by weight of the entire plasticizer. The weight ratio of the plasticizing component excluding the polylactic acid segment component of the plasticizer (B) is 5% by weight or more and 30% by weight or less in the polyester film. The polyester film as described. The polyester film according to any one of claims 7 to 9, wherein the plasticizer (B) has a segment composed of a polyalkylene ether. The polyester film according to claim 10, wherein the polyalkylene ether is polyethylene glycol. It is a wrapping film for packaging, The polyester film in any one of Claims 3-11 characterized by the above-mentioned.