JP5061868B2 - Polylactic acid film - Google Patents

Description

  The present invention relates to a polylactic acid resin film excellent in flexibility, impact resistance and dimensional stability, and excellent in blocking resistance and bleed resistance, and in particular, good quality can be obtained in an inflation film forming method.

  In recent years, global warming due to an increase in the concentration of carbon dioxide in the atmosphere has become a global problem, and various industrial fields are actively developing technologies to reduce carbon dioxide emissions into the atmosphere. . In the field of plastic products, conventionally, plastics produced from general-purpose petroleum-derived raw materials have been incinerated after use and released into the atmosphere as carbon dioxide gas. Attention is focused on plant-derived plastics derived from gas. In particular, research and development for the practical use of polylactic acid, which is excellent in transparency and relatively advantageous in terms of cost, is thriving.

When polylactic acid is applied to soft film applications typified by polyolefins such as polyethylene, it lacks flexibility and impact resistance. Therefore, various attempts have been made to improve these properties and put them into practical use. For example, Patent Document 1 discloses a film made of a composition in which polylactic acid is added with a plasticizer of polyhydric alcohol ester or hydroxy polyvalent carboxylic acid ester, SiO ₂ as an anti-blocking agent, and a lubricant. However, in this technique, the elongation is low and the impact resistance is inferior, and the blocking resistance is not sufficient because of using SiO ₂ having a finer particle diameter than usual, and is an important technique when put to practical use. There is no disclosure of control of thickness errors, so-called film thickness unevenness and shrinkage characteristics, which are important for obtaining a good roll winding form and unwinding property.

  Patent Document 2 discloses an agricultural film made of a composition obtained by adding a biodegradable plasticizer to an aliphatic polyester. However, the present technology mainly relates to aliphatic polyesters other than polylactic acid, and there is no specific disclosure about a film containing polylactic acid as a main component.

  Patent Document 3 discloses a film made of polylactic acid, an aliphatic polyester having a glass transition point of 0 ° C. or less, and a plasticizer. However, there is no disclosure of control of thickness error, so-called film thickness unevenness and shrinkage characteristics, which is important for obtaining a good roll winding shape and unwinding property, which is an important technique for practical use.

  Patent Document 4 discloses a film composed of a lactic acid-based resin and a plasticizer, which is mainly intended for use in stretch packaging. However, with this technology, the anti-blocking property is insufficient and the potential shrinkage property is imparted, so the dimensional stability is inferior. There is no disclosure of control of thickness errors, so-called film thickness unevenness and shrinkage characteristics, which are important for obtaining good performance.

  Patent Document 5 discloses a film obtained by further crystallizing a film made of a plurality of types of polylactic acid having different D-form concentrations and a plasticizer. However, this technique requires a crystallization treatment mainly after heat treatment after winding up the film. However, if a heat treatment in a general roll shape is performed, the plasticizer may actually bleed and block. In addition, the treatment at 60 ° C. for 6 hours as exemplified is disadvantageous in terms of practical use such as being unsuitable for in-line treatment. Furthermore, there is no disclosure at all regarding control of thickness errors, so-called film thickness unevenness and shrinkage characteristics, which are important for obtaining a good roll winding shape and unwinding property.

As described above, there are various types of polylactic acid resin films that are excellent in flexibility, impact resistance, dimensional stability, and excellent in blocking resistance and bleed resistance. However, it has not been achieved yet.
JP-A-8-34913 JP 2000-191805 A JP 2000-273207 A JP 2003-12934 A JP 2006-45290 A

  In view of the background of the prior art, the present invention has excellent flexibility, impact resistance, dimensional stability, and excellent blocking resistance and bleed resistance. It is intended to provide a lactic acid resin film.

In order to solve the above problems, the present invention employs the following means. That is, the polylactic acid resin film of the present invention is
A film produced by an inflation method, the temperature of the annular die used is 160-170 ° C.,
A composition comprising a polylactic acid resin in an amount of 30% to 95% by weight and a plasticizer in an amount of 5% to 30% by weight, and the plasticizer is solid at room temperature,
A film whose elongation in the winding length direction and the width direction (direction perpendicular to the winding length direction) is 200% to 700% and the thickness is 10 μm to 120 μm,
The thickness error ΔTr with respect to the average thickness Ta in the width direction is within ± 10%, and the heat shrinkage ratios Sm (winding length direction) and St (width direction) when treated at 65 ° C. for 30 minutes are as follows: A polylactic acid resin film characterized by satisfying the following conditions.
St ≦ Sm
0 ≦ Sm ≦ 5 (%)
-1 ≦ St ≦ 2 (%)
Moreover, the preferable aspect of the said polylactic acid-type resin film is (1) The composition which comprises a film contains 5 to 45 weight% of aliphatic polyesters and / or aliphatic aromatic polyesters other than polylactic acid. (2) The composition constituting the film contains 5% by weight or more and 45% by weight or less of the polybutylene succinate resin, and (3) the composition constituting the film contains 0.1% by weight or more of the organic lubricant. (4) The plasticizer contained in the composition constituting the film contains a polyether segment and / or a polyester segment as a plasticizing component, and has a number average molecular weight in one molecule. It is a block copolymer having one or more polylactic acid segments of 1,200 or more and 10,000 or less.

  According to the present invention, there is provided a polylactic acid-based resin film that is excellent in flexibility, impact resistance, dimensional stability, excellent in blocking resistance, and bleed resistance, and is particularly good in the inflation film forming method. Is done. The polylactic acid film of the present invention is mainly used for agricultural and forestry applications such as agricultural multi-films and pine worm fumigation sheets that require flexibility and impact resistance, food bags such as garbage bags and compost bags, and vegetables and fruits. It can be preferably used for various packaging applications such as bags for goods and bags for various industrial products.

  The present invention is a polylactic acid resin film that is excellent in the above-mentioned problems, that is, excellent in flexibility, impact resistance, dimensional stability, and excellent in blocking resistance and bleed resistance, particularly in an inflation film forming method. As a result of diligent investigation, the thickness error has a specific composition, specific elongation, and thickness, and is an important technology for practical use and important for obtaining good roll form and unwinding properties. This is the first successful solution to this problem by keeping the so-called film thickness unevenness and shrinkage characteristics within certain conditions.

  Hereinafter, the polylactic acid resin film of the present invention will be described.

  The polylactic acid resin used in the polylactic acid resin film of the present invention is mainly composed of L-lactic acid and / or D-lactic acid, and the component derived from lactic acid is 70% by weight to 100% by weight. Homopolylactic acid composed of L-lactic acid and / or D-lactic acid is preferably used.

  The polylactic acid resin used in the present invention preferably has crystallinity. The polylactic acid resin has crystallinity when the polylactic acid resin is sufficiently crystallized under heating and then subjected to differential scanning calorimetry (DSC) measurement in an appropriate temperature range. This means that the heat of crystal melting derived from is observed. When the polylactic acid resin used in the present invention has crystallinity, it is suitable for imparting blocking resistance when a composition containing the polylactic acid resin is used as a film. In general, homopolylactic acid has higher melting point and crystallinity as the optical purity is higher. The melting point and crystallinity of polylactic acid are affected by the molecular weight and the catalyst used during polymerization, but normally, homopolylactic acid having an optical purity of 98% or higher has a melting point of about 170 ° C. and a relatively high crystallinity. Further, as the optical purity is lowered, the melting point and crystallinity are lowered. For example, homopolylactic acid having an optical purity of 88% has a melting point of about 145 ° C., and homopolylactic acid having an optical purity of 75% has a melting point of about 120 ° C. It is. Homopolylactic acid with an optical purity lower than 70% does not show a clear melting point and is amorphous.

  The polylactic acid resin used in the present invention can be mixed with crystalline homopolylactic acid and amorphous homopolylactic acid for the purpose of imparting or improving necessary functions depending on the application used as a film. . 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. When a relatively high heat resistance is desired when a polylactic acid resin film is used, it is preferable that at least one of the polylactic acid resins used contains polylactic acid having an optical purity of 95% or more.

  The polylactic acid resin used in the present invention has a weight average molecular weight of usually at least 50,000, preferably 80,000 to 400,000, and more preferably 100,000 to 300,000. In addition, a weight average molecular weight here means the molecular weight which measured with the chloroform solvent by the gel permeation chromatography (GPC), and was computed by the polymethylmethacrylate conversion method.

  By setting the weight average molecular weight of the polylactic acid-based resin to at least 50,000, the mechanical properties can be excellent when a composition containing the polylactic acid-based resin is processed into a film.

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

  The production method of the polylactic acid-based resin will be described later in detail, but a known polymerization method can be used, and examples thereof include a direct polymerization method from lactic acid and a ring-opening polymerization method via lactide.

  The polylactic acid resin film of the present invention is composed of a composition containing 30% by weight or more and 95% by weight or less of the polylactic acid resin described above. When the composition constituting the polylactic acid-based resin film contains less than 30% by weight of the polylactic acid-based resin, it is insufficient as a practical technology for plant-derived materials, which is the object of the present invention. Moreover, when the composition which comprises a polylactic acid-type resin film contains polylactic acid-type resin more than 95 weight%, when it is set as a polylactic acid-type resin film, sufficient softness | flexibility cannot be obtained.

  Further, as will be described later, the polylactic acid resin film of the present invention preferably contains an aliphatic polyester other than polylactic acid and / or an aliphatic aromatic polyester and an organic lubricant in addition to the polylactic acid resin and the plasticizer. From such a viewpoint, it is preferable that the composition constituting the polylactic acid resin film of the present invention contains 30% by weight or more and 89% by weight or less of the above-mentioned polylactic acid resin.

  The polylactic acid resin film of the present invention is required to be composed of a composition containing a plasticizer in an amount of 5% by weight to 30% by weight. When the composition constituting the polylactic acid-based resin film contains less than 5% by weight of a plasticizer, sufficient flexibility cannot be obtained when the film is formed. Moreover, when the composition which comprises said polylactic acid-type resin film contains a plasticizer more than 30 weight%, the rigidity at the time of setting it as a film is inadequate, and it is inferior to handleability, inferior to intensity | strength, durability, and practicality. Damage to the plasticizer bleedout becomes large and lacks practicality. Furthermore, it becomes difficult to impart an important shrinkage property to obtain a good roll winding shape and unwinding property, which will be described later. .

  The content of the plasticizer is preferably 9 to 25% by weight in the composition constituting the polylactic acid resin film.

Furthermore, from the viewpoint of durability at the time of storage before use including suppression of bleed out of plasticizer, blocking of film, and dimensional stability, the plasticizer used in the present invention is, for example, polyethylene having a number average molecular weight of 1,000 or more. glycols such as those that are solid at room temperature. From the same viewpoint, the plasticizer used in the present invention contains a polyether-based segment and / or a polyester-based segment as a plasticizing component, and has a number average molecular weight of 1,200 to 10,000 in one molecule. it is good preferable a block copolymer having a polylactic acid segment more than one.

  The block copolymer (hereinafter referred to as “block copolymer plasticizer”), which is a preferred embodiment of the plasticizer used in the present invention, will be described below.

  The weight ratio of the polylactic acid segment component contained in the block copolymer plasticizer is preferably less than 50% by weight of the entire block copolymer plasticizer, because a desired flexibility can be imparted with a smaller amount of addition. It is preferable from the viewpoint of bleed-out suppression that it is more than% by weight. Further, the number average molecular weight of the polylactic acid segment in one molecule of the block copolymer plasticizer is preferably 1,200 or more and 10,000 or less. When the polylactic acid segment of the block copolymer plasticizer is 1,200 or more, sufficient affinity is produced between the block copolymer plasticizer and the polylactic acid resin, and a part of the segment Is incorporated into a crystal formed from a polylactic acid resin as a base material, thereby causing the plasticizer molecule to be anchored to the base material, and exerts a great effect on the bleed-out suppression of the block copolymer plasticizer. The number average molecular weight of the polylactic acid segment of the block copolymer plasticizer is preferably 2,000 or more and less than 6,000. The polylactic acid segment of the block copolymer plasticizer has a component derived from L-lactic acid of 95% by weight to 100% by weight, or a component derived from D-lactic acid of 95% by weight to 100% by weight. % Or less is preferable because bleeding out is particularly suppressed.

  In addition, the block copolymer plasticizer has a polyether segment and / or a polyester segment, but when it has a polyether segment, from the viewpoint that a desired flexibility can be imparted by adding a smaller amount, More preferably, the segment has a segment made of polyalkylene ether, and more preferably has a segment made of polyethylene glycol. When the block copolymer plasticizer has a polyalkylene ether such as polyethylene glycol, polypropylene glycol, or polyethylene glycol / polypropylene glycol copolymer, especially a polyether segment such as polyethylene glycol, it has an affinity for polylactic acid resin. Since it is high, it is excellent in reforming efficiency, and is particularly preferable because a desired flexibility can be imparted by adding a small amount of plasticizer.

  In addition, when the block copolymer plasticizer has a segment composed of a polyalkylene ether, the polyalkylene ether segment portion tends to be easily oxidized or thermally decomposed when heated at the time of molding or the like. It is preferable to use a hindered amine-based antioxidant or a phosphorus-based heat stabilizer in combination.

  When the block copolymer plasticizer has a polyester-based segment, polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate · 3-hydroxyvalerate), polycaprolactone, or ethylene glycol, Polyesters composed of aliphatic diols such as 1,4-butanediol and aliphatic dicarboxylic acids such as succinic acid and adipic acid are preferably used as the polyester-based segment. In addition, for reasons such as productivity and cost of the plasticizer, when it is used as either one of the polyether-based segment and the polyester-based segment, from the viewpoint that desired flexibility can be imparted by adding a smaller amount of the plasticizer. It is preferable to use a polyether-based segment.

  Furthermore, the number average molecular weight of the polyether segment and / or the polyester segment in one molecule of the block copolymer plasticizer is preferably 7,000 or more and less than 20,000. By setting the above range, the composition constituting the polylactic acid-based resin film has sufficient flexibility, and the melt viscosity is set to an appropriate level when the composition includes a plasticizer and a polylactic acid-based resin. And film forming processability such as an inflation film forming method can be stabilized.

  In the polylactic acid-based resin film of the present invention, it is important that the elongation in the winding length direction and the width direction (direction perpendicular to the winding length direction) is 200% or more and 700% or less. In both the winding length direction and the width direction (direction perpendicular to the winding length direction), if the elongation is less than 200%, the impact resistance is insufficient, such as agricultural multi-film and pine worm fumigation sheets. It is easy to break when used for agriculture and forestry, garbage bags, compost bags, or various packaging applications, and is not practical. Further, if the elongation exceeds 700%, it is easy to cause tarmi and wrinkles during roll-to-roll running and winding, and good roll winding and unwinding properties cannot be obtained. From the same viewpoint, it is preferable that the elongations in the winding length direction and the width direction (direction perpendicular to the winding length direction) are both 250% or more and 500% or less.

  It is important that the polylactic acid resin film of the present invention is a film having a thickness of 10 μm or more and 120 μm or less. When the thickness is less than 10 μm, the film is not sufficiently firm and is inferior in handleability, and it is difficult to impart a good roll form and unwinding property. In addition, when the thickness exceeds 120 μm, sufficient flexibility cannot be obtained, and it can be used for agricultural and forestry applications such as agricultural multi-films and pine worm fumigation sheets, garbage bags, compost bags, or various packaging applications. It will be inferior in handleability. In particular, in the inflation film-forming method, bubbles tend to be unstable due to their own weight, and it becomes difficult to impair the flatness and give a good roll winding shape. From the same viewpoint, the polylactic acid resin film of the present invention preferably has a thickness of 15 μm or more and 120 μm or less.

  Furthermore, it is important that the polylactic acid resin film of the present invention has an average thickness in the width direction: thickness error with respect to Ta: ΔTr within ± 10%. When ΔTr exceeds the range of ± 10%, when rolled up in a roll shape, the position thicker than the average thickness in the film width direction swells into a hump shape with a winding diameter larger than its surroundings, and more than the average thickness. In a thin position, it becomes difficult to provide a good roll winding shape, for example, the winding diameter is smaller than that of the surrounding area and the winding is depressed or the winding hardness is extremely lowered. Such a tendency is markedly greater in polylactic acid resin films to which a plasticizer is added compared to other aliphatic polyester cases such as poly (butylene succinate) and poly (butylene adipate terephthalate). Since the crystallinity is relatively low, the winding shape tends to be further deteriorated by so-called winding tightening, in which film shrinkage gradually occurs even after the winding. In order to suppress this tendency, it is necessary to set the shrinkage characteristics (heat shrinkage rate) within a certain range as described later. In addition, in the roll as described above, which has a bump-like part or a part that is recessed or has extremely reduced winding hardness depending on the position in the width direction, wrinkles are generated in the rolled state and the wrinkled part is caught smoothly during unwinding. In other words, the film cannot be unwound or the flatness of the unwound film may be poor and the mechanical characteristics may partially deteriorate. From such a viewpoint, ΔTr is preferably within ± 8%, and more preferably within ± 6%.

The polylactic acid-based resin film of the present invention is required to satisfy the following conditions for heat shrinkage ratios: Sm (winding length direction) and St (width direction) when treated at 65 ° C. for 30 minutes.
St ≦ Sm
0 ≦ Sm ≦ 5 (%)
-1 ≦ St ≦ 2 (%)
In the case of Sm> 5 (%) and / or St> 2 (%), the film after winding is gradually contracted with time, and the winding shape is deteriorated by so-called winding. Furthermore, the winding hardness becomes too high, blocking occurs and unwinding becomes unstable. On the other hand, when Sm <0 (%), the film after winding is loosened in the winding length direction over time, the winding shape is deteriorated, and the flatness of the film is lost. Further, in the case of St <-1 (%), the winding shape of the film end portion is deteriorated, the flatness is lost, and the unwinding becomes unstable. Here, when Sm and St are negative values less than 0, it means that the film is stretched.

  Further, in the case of St> Sm, the winding diameter of both end portions in the width direction of the film tends to be smaller than that of the central portion, and when unwinding, tarmi is generated in the central portion, for example, When it is spread as a multi-agricultural film with Malcher, both ends are too stretched and easily broken, resulting in a film lacking practicality.

  The polylactic acid-based resin film of the present invention improves impact resistance and biodegradability, and improves the melt viscosity to form a stable bubble especially in the inflation film-forming method, thereby improving the winding shape. The composition constituting the polylactic acid-based resin film preferably contains 5% by weight or more and 45% by weight or less of an aliphatic polyester and / or an aliphatic aromatic polyester other than polylactic acid. When the content of the aliphatic polyester and / or aliphatic aromatic polyester other than polylactic acid is 5% by weight or more, the improvement effect is easily obtained mainly from the viewpoint of impact resistance, and the content is 45% by weight or less. For example, moderate biodegradability can be imparted mainly in fields that require biodegradability especially for agricultural and forestry applications.

  Examples of aliphatic polyesters and / or aliphatic aromatic polyesters other than polylactic acid include polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate · 3-hydroxyvalerate), and polycaprolactone. Or an aliphatic polyester composed of an aliphatic diol such as ethylene glycol or 1,4-butanediol and an aliphatic dicarboxylic acid such as succinic acid or adipic acid, or poly (butylene succinate / terephthalate) or poly (butylene adipate). A copolymer of an aliphatic polyester such as terephthalate) and an aromatic polyester, polyvinyl alcohol, and the like. Of these, polybutylene succinate resins such as polybutylene succinate and polybutylene succinate adipate are preferably used as those having a large improvement effect in both impact resistance and biodegradability.

  The composition constituting the polylactic acid-based resin film of the present invention preferably contains 0.1% by weight or more and 5% by weight or less of an organic lubricant. In this case, blocking after winding can be favorably suppressed. In addition, problems such as a decrease in melt viscosity and deterioration of workability due to excessive addition of an organic lubricant, or poor appearance such as bleed out and haze up when formed into a film are less likely to occur.

  Examples of organic lubricants include liquid paraffins, natural paraffins, synthetic paraffins, aliphatic hydrocarbons such as polyethylene, stearic acid, lauric acid, hydroxystearic acid, fatty castors such as hard castor oil, stearic acid amide, oleic acid amide, Fatty acid amides such as erucic acid amide, lauric acid amide, ethylene bis stearic acid amide, ethylene bis oleic acid amide, ethylene bis lauric acid amide, fatty acid metal salts such as aluminum stearate, lead stearate, calcium stearate, magnesium stearate , Fatty acid (partial) esters of polyhydric alcohols such as glycerin fatty acid esters and rubitan fatty acid esters, long chain fatty acid esters such as long chain ester waxes such as butyl stearate and montan wax And the like. Among these, stearic acid amide and ethylene bis-stearic acid amide, which are easy to obtain an effect in a small amount due to appropriate compatibility with polylactic acid, are preferable.

  The polylactic acid resin film of the present invention preferably has a haze of 15% or less, and more preferably 10% or less. When the haze is 15% or less, the contents can be easily confirmed when molded into various packaging applications such as bags for foods such as vegetables and fruits, bags for various industrial products, etc. It is often preferable due to its high design properties. In addition, from the general characteristic of polylactic acid, since it is difficult to make it less than 1% as a haze of a polylactic acid-type resin film, a minimum is about 1%.

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

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.

  In addition, when adding particles for the purpose of improving the slipperiness and blocking resistance of processed products, for example, as inorganic particles, various kinds of silicon oxide such as silica, calcium carbonate, magnesium carbonate, barium carbonate, etc. Various sulfates such as carbonate, calcium sulfate and barium sulfate, various composite oxides such as kaolin and talc, various phosphates such as lithium phosphate, calcium phosphate and magnesium phosphate, aluminum oxide, titanium oxide, zirconium oxide, etc. Fine particles composed of various oxides, various salts such as lithium fluoride, and the like can be used.

  As the organic particles, fine particles made of calcium oxalate, terephthalate such as calcium, barium, zinc, manganese, magnesium, or the like are used. Examples of the crosslinked polymer particles include fine particles made of a vinyl monomer such as divinylbenzene, styrene, acrylic acid or methacrylic acid, or a copolymer. In addition, organic fine particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, and thermosetting phenol resin are also preferably used.

  The average particle diameter of both inorganic particles and organic particles 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 polylactic acid-based resin film of the present invention has a reduced strength due to hydrolysis of the polylactic acid-based resin, particularly in applications that do not require biodegradability, such as packaging for various industrial products, or where it is preferable to have storage durability. From the viewpoint of suppressing the above and imparting good durability, the carboxyl group terminal concentration of the film is preferably 0 equivalent / 10 ³ kg or more and 30 equivalent / 10 ³ kg or less, more preferably 20 equivalent / 10 ³ kg or less, more preferably 10 equivalents / 10 ³ kg or less. When the carboxyl group terminal concentration of the film is 30 equivalents / 10 ³ kg or less, the carboxyl group terminal concentration that also serves as a hydrolysis autocatalyst is sufficiently low. There are many cases where this is possible.

Examples of a method for setting the carboxyl group terminal concentration of the film to 30 equivalents / 10 ³ kg or less include, for example, a method of controlling by a catalyst and a thermal history during the synthesis of a polylactic acid resin, a lowering of the extrusion temperature during film formation, or Examples thereof include a method of reducing the heat history such as shortening the residence time, a method of blocking the carboxyl group terminal using a reactive compound, and the like.

  In the method of blocking the carboxyl group terminal using a reactive compound, it is preferable that at least a part of the carboxyl group terminal in the film is blocked, and it is more preferable that the whole amount is blocked. Examples of reactive compounds include condensation reactive compounds such as aliphatic alcohols and amide compounds, and addition reactive compounds such as carbodiimide compounds, epoxy compounds, and oxazoline compounds, but extra by-products are generated during the reaction. An addition reaction type compound is preferable in terms of difficulty, and a carbodiimide compound is particularly preferable from the viewpoint of reaction efficiency.

Next, the method for producing the polylactic acid resin film of the present invention will be specifically described.
The polylactic acid resin in the present invention can be obtained, for example, by the following method. As a raw material, a lactic acid component of L-lactic acid or D-lactic acid is mainly used, and a hydroxycarboxylic acid other than the lactic acid component described above can be used in combination. Further, a cyclic ester intermediate of hydroxycarboxylic acid, for example, lactide, glycolide, etc. can be used as a raw material. Furthermore, dicarboxylic acids and glycols can also be used.

  The polylactic acid resin can be obtained by a method of directly dehydrating and condensing the raw materials or a method of ring-opening polymerization of the cyclic ester intermediate. For example, in the case of producing by direct dehydration condensation, lactic acid or lactic acid and hydroxycarboxylic acid are preferably subjected to azeotropic dehydration condensation in the presence of an organic solvent, particularly a phenyl ether solvent, and particularly preferably a solvent distilled by azeotropic distillation. A polymer having a high molecular weight can be obtained by polymerizing by a method in which water is removed from the solvent and the solvent is brought into a substantially anhydrous state and returned to the reaction system.

  It is also known that a high molecular weight polymer can be obtained by subjecting a cyclic ester intermediate such as lactide to ring-opening polymerization under reduced pressure using a catalyst such as tin octylate. At this time, a method for adjusting the conditions for removing moisture and low molecular weight compounds during heating and refluxing in an organic solvent, a method for suppressing the depolymerization reaction by deactivating the catalyst after completion of the polymerization reaction, and a method for heat-treating the produced polymer Can be used to obtain a polymer with a small amount of lactide.

  Next, in one of the preferred embodiments of the present invention, one molecule that is solid at room temperature has one or more polylactic acid segments having a number average number molecular weight of 1,200 to 10,000, A more specific example of a block copolymer plasticizer having an ether segment and / or a polyester segment will be described.

A polyethylene glycol having a hydroxyl group at both ends (hereinafter, polyethylene glycol is referred to as PEG) is prepared. The number average molecular weight of PEG having hydroxyl ends at both ends (hereinafter, the number average molecular weight of _PEG is referred to as _MPEG ) is usually calculated from the hydroxyl value determined by a neutralization method or the like in the case of a commercially available product. In a system in which lactide w _A parts by weight are added to w _B parts by weight of PEG having hydroxyl groups at both ends, lactide undergoes ring-opening addition polymerization at both hydroxyl ends of PEG and sufficiently reacts. A block copolymer of type (A) -PEG (B) -PLA (A) can be obtained (PLA here indicates polylactic acid). This reaction is performed in the presence of a catalyst such as tin octylate as necessary. The number average molecular weight of one polylactic acid segment of the plasticizer made of this block copolymer can be substantially determined as (1/2) × (w _A / w _B ) × M _PEG . The weight percentage of the total block copolymer plasticizer of the polylactic acid segment component can be substantially determined as _{100 × w A / (w A} + w B)%. Furthermore, the weight ratio of the plasticizer component excluding the polylactic acid segment component to the entire block copolymer plasticizer can be determined to be substantially 100 × w _B / (w _A + w _B )%.

  Block copolymer plasticizer contains a large amount of unreacted PEG, reactants with PEG whose terminal polylactic acid segment number average molecular weight is less than 1,200, by-products such as lactide oligomers, impurities, etc. If included, it is preferable to remove them, for example, by the following purification method. The synthesized block copolymer plasticizer is uniformly dissolved in an appropriate good solvent such as chloroform, and then 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 block copolymer plasticizer in water, the mixture is heated to 50 to 90 ° C. and stirred as necessary, and then the organic phase containing the block copolymer 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. Removal of by-products such as lactide oligomers can prevent a decrease in viscosity when a polylactic acid resin composition is obtained, and the melt viscosity of the composition is set to an appropriate level to stabilize processing. It is also preferable because it can be performed.

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

  In the present invention, a composition containing a polylactic acid resin component and a plasticizer component, an aliphatic polyester other than polylactic acid and / or an aliphatic aromatic polyester, or other components such as an organic lubricant (polylactic acid of the present invention) In obtaining the composition constituting the resin film), it is possible to produce a composition by uniformly mixing a solution in which each component is dissolved in a solvent, and then removing the solvent. It is preferable to employ a melt-kneading method in which a composition is produced by melt-kneading each component, which is a practical production method that does not require steps such as solvent removal. The melt kneading method is not particularly limited, and a commonly used known mixer such as a kneader, roll mill, Banbury mixer, single-screw or twin-screw extruder can be used. Among these, from the viewpoint of productivity, it is preferable to use a single screw or twin screw extruder.

  The order of mixing is not particularly limited. For example, after a dry blend of a polylactic acid resin and a plasticizer that is solid at room temperature, a method of using a melt kneader, or a plasticizer that is solid at room temperature in advance. Examples thereof include a method of melt-kneading the master batch, the polylactic acid resin, and the other components described above after preparing the melt-kneaded master batch. Further, if necessary, a method of melt-kneading other components at the same time, or preparing a master batch in which a polylactic acid-based resin and other additives are melt-kneaded in advance, the master batch, the polylactic acid-based resin, and a plasticizer component You may use the method of melt-kneading. In addition, when a liquid component such as a plasticizer is added at room temperature, it can be added from the feed hole vent hole of the extruder using a metering pump, separately from the solid component at room temperature.

  The temperature at the time of melt kneading is preferably in the range of 150 ° C. to 240 ° C., and more preferably in the range of 200 ° C. to 220 ° C. from the viewpoint of preventing the deterioration of the polylactic acid resin.

  The polylactic acid-based resin film of the present invention can be obtained, for example, by a known film production method such as a known inflation method or T-die casting method using the composition obtained by the above-described method.

  In producing the polylactic acid-based resin film of the present invention, for example, when the composition obtained by the above-described method is once chipped, and melt-kneaded again to perform extrusion / film formation, the chip is kept at 60 to 110 ° C. It is preferable to use a composition containing a polylactic acid resin or the like having a moisture content of 1200 ppm or less by drying for 6 hours or more. Furthermore, it is preferable to reduce the lactide content in the composition containing the polylactic acid resin or the like by vacuum drying under a high vacuum with a degree of vacuum of 10 Torr or less. By reducing the water content of the composition containing a polylactic acid-based resin to 1200 ppm or less and the lactide content, hydrolysis during melt-kneading can be prevented, thereby preventing a decrease in molecular weight. This is also preferable because the melt viscosity can be adjusted to an appropriate level and the film forming process can be stabilized. From the same point of view, when chipping or melt extrusion / film formation is performed once, melt extrusion is performed while removing volatiles such as moisture and low molecular weight substances using a twin-screw extruder with a vent hole. It is preferable.

  When the polylactic acid-based resin film of the present invention is produced by an inflation method, for example, a composition containing a polylactic acid-based resin or the like prepared by the above-described method is melt-extruded using a twin-screw extruder with a vent hole. Guided to an annular die, extruded from the annular die, supplied with dry air inside to form a balloon (bubble), air-cooled and solidified uniformly with an air ring, and taken up at a predetermined take-up speed while folded flat with a nip roll After that, if necessary, both ends or one end may be cut open and wound.

  In this case, the thickness may be adjusted to 10 μm or more and 120 μm or less depending on the discharge amount from the annular die, the take-up speed of the nip roll, and the bubble blowing ratio. In order to suppress the thickness error ΔTr with respect to the thickness Ta, it is preferable to use a spiral die for the annular die.

  Further, the extrusion temperature of the composition containing polylactic acid resin or the like is usually in the range of 150 to 240 ° C., but the thickness relative to the average thickness Ta in the width direction in order to give a good roll winding shape and unwinding property. The temperature of the annular die is controlled in order to suppress the error ΔTr and control the St ≦ Sm, 0 ≦ Sm ≦ 5 (%), and −1 ≦ St ≦ 2 (%) by giving an appropriate heat shrinkage rate. Is important, and the temperature of the annular die is in the range of 150 to 190 ° C, preferably 150 to 170 ° C. If the temperature of the annular die is less than 150 ° C., the temperature at which the composition is extruded is too low, the molding behavior at the time of blow-up immediately after discharge becomes uneven, the thickness accuracy deteriorates, and the winding shape becomes poor. When a film is formed because the stress at the time of up is too high, the heat shrinkage rate is high, and the winding shape is further deteriorated by so-called winding tightening over time. On the other hand, when the temperature of the annular die exceeds 190 ° C., the viscosity of the composition is too low, the thickness accuracy is deteriorated and the winding shape is poor, and the bubble formation itself tends to be unstable. From the same viewpoint, the temperature of the annular die is more preferably 160 to 170 ° C.

  The blow ratio of the bubble depends on the relationship between the discharge amount and the take-up speed of the nip roll, but the film may be anisotropic if it is too low or too high. It tends to be unstable and is usually in the range of 2.0 to 4.0.

  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.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited thereto.
[Measurement and evaluation method]
Measurements and evaluations shown in the examples were performed under the following conditions.

(1) Average thickness in the width direction: Ta (μm), thickness error relative to Ta: ΔTr (%)
The thickness at each position was measured at intervals of 5 cm from one end to the other end along the width direction of the film sample. The measurement was performed with a dial gauge according to JIS B7503, and the average thickness of each measurement value: Ta (μm) was determined. Further, an error in thickness with respect to Ta: ΔTr (%) was calculated according to the following equation.
Maximum value of ΔTr (%) = {(maximum value of thickness) −Ta} / Ta × 100
ΔTr minimum value (%) = {(minimum thickness value) −Ta} / Ta × 100
(2) Tensile modulus (MPa), elongation (%)
The test direction was taken as 150 mm (longitudinal direction) × 10 mm (width direction) as the longitudinal direction, and measurement was performed in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH. Tensilon universal testing machine UTC-100 (manufactured by Orientec Co., Ltd.) was used to conduct a tensile test under the conditions of an initial length between chucks of 50 mm and a tensile speed of 300 mm / min, and using the first linear part of the stress-strain curve, The difference in stress between the two points was divided by the difference in strain between the two points, and an average value was obtained for a total of five tests, which was taken as the tensile modulus in the winding length direction. In addition, the strain at the time of rupture of the sample was read from the stress-strain curve, the average value was obtained for a total of five tests, and this was defined as the elongation in the winding length direction.

  The width direction was also measured by the same method.

(3) Impact strength (kN · m / mm)
Using a film impact tester (manufactured by Toyo Seiki Co., Ltd.), impact strength was measured in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH using a hemispherical impact head having a diameter of 1/2 inch. The measurement was performed 5 times for each level, and the average value of the 5 measurements was obtained. Furthermore, the average thickness was determined by dividing by Ta × 10 ⁻³ (mm) and obtained as a value per unit thickness.

(4) Thermal contraction rate (%)
Cut out the test direction as a longitudinal direction into 140 mm × 10 mm, put a rating line between 100 mm in the longitudinal direction, hold the inside at 65 ° C. and treat it in a dry heat oven for 30 minutes, then measure the dimension between the rating lines, The shrinkage was calculated according to the following formula. The measurement was performed five times for each level, and the heat shrinkage rate Sm in the winding length direction was determined from the average value of the five measurements.
Shrinkage rate (%) = {(dimension before shrinkage) − (dimension after shrinkage)} / (dimension before shrinkage) × 100
The heat shrinkage rate St in the width direction was obtained by the same method.

(5) Haze value (%)
The haze value was measured using a haze meter HGM-2DP type (manufactured by Suga Test Instruments Co., Ltd.). The measurement was performed 5 times for each level, and the average value of the 5 measurements was obtained.

(6) Roll roll appearance and appearance After the roll sample is stored for 3 days in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH, the size of the roll sample is the largest and smallest in the width direction of the roll sample. Was measured, and the ratio of the difference between the maximum value and the minimum value of the winding diameter to the minimum value: D (%) was determined and judged according to the following criteria.
A: D ≦ 1%
○: 1% <D ≦ 1.5%
Δ: 1.5% <D ≦ 3%
×: 3% <D
(7) Unwinding property After the roll sample is stored for 3 days in an atmosphere at a temperature of 23 ° C. and a humidity of 65% RH, an iron shaft having a diameter smaller than the inner diameter of the paper tube is passed through the paper tube of the roll sample. The roll is placed in a state where the roll can be rotated horizontally and freely, and the state of unwinding when the film is unwound at a speed of 10 m / min is visually observed. It was judged.
(Double-circle): It can unwind smoothly without a problem.
○: Discontinuous unwinding from time to time due to slight wrinkles and blocking.
Δ: Discontinuous unwinding due to wrinkles and blocking.
X: Due to wrinkles and blocking, the film is pulled and deformed or broken during unwinding.

(8) Wrinkles and Tarmi After the roll sample is stored for 3 days in an atmosphere of temperature 23 ° C. and humidity 65% RH, an iron shaft having a diameter smaller than the inner diameter of the paper tube is passed through the paper tube of the roll sample. The roll was placed in a state where it was hooked horizontally and freely rotated, the film was unwound from the roll sample by about 2 m in the horizontal direction, visually observed, and judged according to the following criteria.
○: Wrinkles and tarmi were not observed, and there was no problem with flatness.
Δ: Although wrinkles and tarmi are slightly observed, if the roll is fixed in a state where it cannot be freely rotated, and a strain of 1% or less is applied by applying tension in the film winding direction, no wrinkles or tarmi are observed.
X: Wrinkles and tarmi are also observed in the above.
[Polylactic acid resin used]
(Polylactic acid PL1)
Weight average molecular weight = 200,000, D-form content = 12.0%, melting point = none, moisture content = 490 ppm,
(Polylactic acid PL2)
Weight average molecular weight = 220,000, D-form content = 1.4%, melting point = 166 ° C.
Moisture content = 360 ppm,
(Polylactic acid PL3)
Weight average molecular weight = 220,000, D-form content = 5.0%, melting point = 150 ° C.
Moisture content = 360 ppm,
The weight average molecular weight was measured by using Waters 2690 manufactured by Japan Waters Co., Ltd., using polymethyl methacrylate as a standard, a column temperature of 40 ° C., and a chloroform solvent.
[Plasticizer used]
(Plasticizer PS1)
Acetyltributyl citrate (Morimura Corporation, trade name “Citroflex A-4”)
(Plasticizer PS2)
Polyethylene glycol (manufactured by Sanyo Chemical Industries, trade name “PEG-10000”)
(Plasticizer PS3)
By mixing 62 parts by weight of polyethylene glycol having a number average molecular weight of 8,000, 38 parts by weight of L-lactide and 0.05 parts by weight of tin octylate and polymerizing at 160 ° C. for 3 hours in a nitrogen atmosphere, both ends of polyethylene glycol are mixed. A plasticizer S1 having a polylactic acid segment having a number average molecular weight of 2,500 was obtained. Immediately after obtaining the plasticizer S1, moisture-proof packaging was performed and stored. When the water content was measured, it was 1650 ppm.
[Used aliphatic polyester resin, aliphatic aromatic polyester resin]
(Polyester PA1)
Polybutylene succinate and adipate resin (made by Showa Polymer Co., Ltd., trade name “Bionore” # 3001)
(Polyester PA2)
Polybutylene succinate and adipate resin (Mitsubishi Chemical Corporation, trade name “GSPla” AD92W)
(Polyester PA3)
Polybutylene adipate terephthalate resin (BASF, trade name "Ecoflex")
[Used organic lubricant]
(Lubricant SL1)
Stearic acid amide (Nippon Yushi Co., Ltd., trade name "Alflow S-10")
[Preparation of polylactic acid resin film]
Example 1
A mixture of 60% polylactic acid PL1, 17.6% polylactic acid PL2, 21.4% plasticizer PS3 and 1.0% lubricant SL1 is a vacuum vent with a cylinder diameter of 190 ° C and a screw diameter of 44 mm. It was used in a twin screw extruder, melted and kneaded while degassing the vacuum vent portion, and then homogenized to obtain a composition 1 that was chipped.

  After drying this composition with dehumidified hot air at a temperature of 100 ° C. and a dew point of −25 ° C. for 10 hours, a composition shown in Table 1 as a mixture of 70% by weight of composition 1 and 30% by weight of polyester PA1 was finally obtained. Supplied to a single-screw extruder with a screw diameter of 65 mm with a cylinder temperature of 190 ° C and a spiral annular die with a diameter of 250 mm, a lip clearance of 1.3 mm, and a temperature of 165 ° C. Then, the sheet was cooled with a cooling ring, taken up at 20 m / min while being folded with a nip roll above the die, cut at both ends with an edge cutter and cut into two sheets, and each film was wound with a winder. A film having a final thickness of 20 μm was obtained by adjusting the discharge amount. The film formation was stable without breaking for 12 hours. The evaluation results of the obtained film are shown in Table 1.

(Example 2)
A mixture of 69.6% by weight of polylactic acid PL1, 15.9% by weight of polylactic acid PL2, 13.6% by weight of plasticizer PS2 and 1.0% by weight of lubricant SL1 is a cylinder having a screw diameter of 44 mm and a cylinder temperature of 190 ° C. It was used for the twin-screw extruder with a vacuum vent, and it melt-kneaded and homogenized, deaerating a vacuum vent part, and obtained the composition 2 which was chipped.

The resin composition was dried with dehumidified hot air at a temperature of 100 ° C. and a dew point of −25 ° C. for 10 hours, and then the composition 2 was 70% by weight and polyester PA1 was 30% by weight. A film having a final thickness of 20 μm was obtained in the same manner as in Example 1 except that it was used. The film formation was stable without breaking for 12 hours. The evaluation results of the obtained film are shown in Table 1.
( Reference Example 1 )
A film having a final thickness of 20 μm was obtained in the same manner as in Example 2 except that the plasticizer PS1 was used instead of the plasticizer PS2. The film formation was stable without breaking for 12 hours. The evaluation results of the obtained film are shown in Table 1.
( Reference Example 2 )
A film having a final thickness of 20 μm was obtained in the same manner as in Reference Example 1 except that the plasticizer PS1 was used instead of the plasticizer PS2 and the polyester PA3 was used instead of the polyester PA1. The film formation was stable without breaking for 12 hours. The evaluation results of the obtained film are shown in Table 1.
( Reference Example 3 )
A mixture of 74.6% by weight of polylactic acid PL1, 16.9% by weight of polylactic acid PL2, and 8.6% by weight of plasticizer PS2 was supplied to a twin screw extruder equipped with a vacuum vent with a cylinder diameter of 190 ° C. and a screw diameter of 44 mm. Then, the composition 5 was obtained as a chip after melt-kneading and homogenizing while degassing the vacuum vent part.

This resin composition was dried with dehumidified hot air at a temperature of 100 ° C. and a dew point of −25 ° C. for 10 hours, and finally the composition shown in Table 1 as a mixture of 70 wt% of composition 5 and 30 wt% of polyester PA1 was obtained. A film having a final thickness of 20 μm was obtained in the same manner as in Reference Example 1 except that it was used. The film formation was stable without breaking for 12 hours. The evaluation results of the obtained film are shown in Table 1.
(Example 3 )
A mixture of polylactic acid PL1 (68.1% by weight), polylactic acid PL3 (22.4% by weight) and plasticizer PS2 (9.5% by weight) was supplied to a twin screw extruder equipped with a vacuum vent with a cylinder diameter of 190 ° C. and a screw diameter of 44 mm. Then, the composition 6 was obtained as a chip after melt-kneading and homogenizing while degassing the vacuum vent part.

A film having a final thickness of 20 μm was obtained in the same manner as in Reference Example 1 except that this resin composition was dried with dehumidified hot air at a temperature of 100 ° C. and a dew point of −25 ° C. for 10 hours and then used as it was. The film formation was stable without breaking for 12 hours. The evaluation results of the obtained film are shown in Table 1.
(Example 4 )
A film having a final thickness of 100 μm was obtained in the same manner as in Reference Example 1 except that polyester PA2 was used instead of polyester PA1, except that the discharge rate was adjusted with a nip roll take-up speed of 5 m / min. The film formation was stable without breaking for 12 hours. The evaluation results of the obtained film are shown in Table 1.
(Example 5 )
A mixture of 31.2% by weight of polylactic acid PL1, 11.1% by weight of polylactic acid PL2, 27% by weight of plasticizer PS3, 30% by weight of polyester PA1, and 0.7% by weight of lubricant SL1 is a cylinder temperature of 190 ° C. This was used in a twin screw extruder with a vacuum vent of 44 mm, melt-kneaded and homogenized while degassing the vacuum vent, and then weighed with a gear pump. Diameter 250 mm, lip clearance 1.3 mm, temperature 165 Extruded upwards in a bubble shape at a blow ratio of 3.4 from a spiral annular die at ℃, air-cooled with a cooling ring, taken up at 20 m / min while folding with a nip roll above the die, and both ends with an edge cutter The film was cut into two sheets, and each film was wound up with a winder. A film having a final thickness of 20 μm was obtained by adjusting the discharge amount. The film formation was stable without breaking for 12 hours. The evaluation results of the obtained film are shown in Table 1.
(Example 6 )
Screw diameter of a mixture of 57.2% by weight of polylactic acid P 3 L1, 19.8% by weight of polylactic acid PL2, 22.2% by weight of plasticizer PS3 and 1.0% by weight of lubricant SL1 at a cylinder temperature of 190 ° C. The composition 9 was subjected to a 44-mm twin-screw extruder with a vacuum vent and melt-kneaded and homogenized while degassing the vacuum vent, and then chipped composition 9 was obtained.

This resin composition was dried with dehumidified hot air at a temperature of 100 ° C. and a dew point of −25 ° C. for 10 hours, and then the composition 9 was 90% by weight and polyester PA1 was 10% by weight as a mixture finally shown in Table 1. A film having a final thickness of 20 μm was obtained in the same manner as in Example 2 except that it was used. The film formation was stable without breaking for 12 hours. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 1)
A mixture of 75% by weight of polylactic acid PL1, 22% by weight of polylactic acid PL2, and 3% by weight of plasticizer PS3 was supplied to a twin screw extruder with a vacuum vent with a cylinder diameter of 190 ° C. and a screw diameter of 44 mm, and the vacuum vent part was removed. After melt-kneading and homogenizing with air, we continue to measure with a gear pump. From a spiral annular die with a diameter of 250 mm, a lip clearance of 1.3 mm, and a temperature of 165 ° C., the bubble ratio is upward at a bubble ratio of 3.4 Then, the sheet was cooled with a cooling ring, taken up at 20 m / min while being folded with a nip roll above the die, cut at both ends with an edge cutter and cut into two sheets, and each film was wound with a winder. A film having a final thickness of 20 μm was obtained by adjusting the discharge amount. The film formation was stable without breaking for 12 hours. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 2)
24% by weight of polylactic acid PL1, 10% by weight of polylactic acid PL2, 35% by weight of plasticizer PS3, 30% by weight of polyester PA1, 1.0% by weight of lubricant SL1, and a screw diameter of 44 mm at a cylinder temperature of 190 ° C. And melt-kneaded while homogenizing while venting the vacuum vent part, then weighed with a gear pump, spiral type with diameter 250mm, lip clearance 1.3mm, temperature 165 ℃ Extruded upwards in a bubble shape from a circular die at a blow ratio of 3.4, air-cooled by a cooling ring, taken up at 20 m / min while being folded by a nip roll above the die, and cut at both ends with an edge cutter. It was cut into sheets and each film was wound with a winder. A film having a final thickness of 20 μm was obtained by adjusting the discharge amount. Although the film formation was not broken for 12 hours, the bubble was unstable, the fluctuation of the folding width when folded by the nip roll was relatively large, and wrinkles were sometimes generated during the nip. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 3)
In the same manner as in Example 1, a film having a final thickness of 8 μm was obtained by further adjusting the discharge amount. The film formation broke 5 times in 12 hours. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 4)
A film having a final thickness of 150 μm was obtained in the same manner as in Example 1, except that the discharge rate was adjusted with a nip roll take-up speed of 4 m / min. Although the film formation was not broken for 12 hours, the bubble was unstable, the fluctuation of the folding width when folded by the nip roll was relatively large, and wrinkles were sometimes generated during the nip. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 5)
In the same manner as in Example 1, except that a screw diameter of 65 mm and a cylinder temperature of 200 ° C. were supplied to a single screw extruder, extruded from a spiral type annular die having a temperature of 200 ° C., and the discharge amount was adjusted to obtain a film having a final thickness of 20 μm. Obtained. Although the film formation was not broken for 12 hours, the fluctuation of the folding width when the bubble was unstable and it was folded by the nip roll was relatively large. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 6)
A film having a final thickness of 20 μm was obtained in the same manner as in Example 1, except that the discharge rate was adjusted with a nip roll take-up speed of 35 m / min. The film formation was broken twice in 12 hours. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 7)
In the same manner as in Example 1, except that a spiral annular die having a diameter of 150 mm was used, the tube was extruded upward at a blow ratio of 4.7, and the discharge rate was adjusted by adjusting the discharge amount of the nip roll to 15 m / min. A film having a thickness of 20 μm was obtained. The film formation broke 4 times in 12 hours. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 8)
A film having a final thickness of 20 μm was obtained in the same manner as in Example 1 except that the film was extruded from a spiral annular die having a temperature of 145 ° C. to adjust the discharge amount. The film formation broke 4 times in 12 hours. The evaluation results of the obtained film are shown in Table 1.

The polylactic acid-based resin films of Examples 1 to 6 have flexibility (tensile modulus) and impact resistance (impact strength) within practical ranges, and are excellent in dimensional stability, blocking resistance, and bleed resistance. The film was excellent in quality such as roll appearance, appearance, unwinding property, wrinkles and tarmi.

  On the other hand, in the comparative example, the plasticizer content was less than 5% by weight, and therefore the film having the elongation of less than 200% was insufficient in flexibility and impact resistance (Comparative Example 1).

  Conversely, a film with a plasticizer content of more than 30% by weight has high flexibility and impact resistance, but has a high heat shrinkage rate, and plasticizer bleed-out is also observed. Unwinding quality, wrinkles, tarmi, and other qualities were insufficient (Comparative Example 2).

  When the film thickness was less than 10 μm, in addition to being slightly inferior in handleability due to lack of stiffness as a film, some blocking was also observed, and in particular, unwinding property was particularly insufficient (Comparative Example 3). .

  On the contrary, when the film thickness exceeds 120 μm, in addition to being slightly stiff, the bubble was uneasy and the flatness was impaired. Especially, the roll appearance and the quality of the appearance were insufficient (Comparative Example) 4).

  When the error in thickness exceeded ± 10%, the quality of rolled rolls, appearance, wrinkles, tarmi, etc. was particularly insufficient (Comparative Example 5).

  In the case of heat shrinkage ratio: Sm> 5 (%), so-called winding tightening and therefore blocking occurred, and in particular, the roll winding shape and appearance were insufficient (Comparative Example 6).

  In the case of thermal shrinkage ratio: St> Sm, the winding diameter of both end portions in the width direction of the film is also smaller than that of the central portion, so that tarmi is generated in the central portion. The quality of talmi and the like was insufficient (Comparative Example 7).

Claims (5)

A film produced by an inflation method, the temperature of the annular die used is 160-170 ° C.,
A composition comprising a polylactic acid resin in an amount of 30% to 95% by weight and a plasticizer in an amount of 5% to 30% by weight, and the plasticizer is solid at room temperature,
A film whose elongation in the winding length direction and the width direction (direction perpendicular to the winding length direction) is 200% to 700% and the thickness is 10 μm to 120 μm,
The thickness error ΔTr with respect to the average thickness Ta in the width direction is within ± 10%, and the heat shrinkage ratios Sm (winding length direction) and St (width direction) when treated at 65 ° C. for 30 minutes are as follows: A polylactic acid resin film characterized by satisfying the following conditions.
St ≦ Sm
0 ≦ Sm ≦ 5 (%)
-1 ≦ St ≦ 2 (%)   The polylactic acid resin film according to claim 1, wherein the composition contains 5% by weight or more and 45% by weight or less of an aliphatic polyester and / or an aliphatic aromatic polyester other than polylactic acid.   The polylactic acid resin film according to claim 2, wherein the aliphatic polyester and / or the aliphatic aromatic polyester is a polybutylene succinate resin.   The polylactic acid resin film according to any one of claims 1 to 3, wherein the composition contains 0.1 wt% or more and 5 wt% or less of an organic lubricant.   The block in which the plasticizer contains a polyether segment and / or a polyester segment as a plasticizing component and has at least one polylactic acid segment having a number average molecular weight of 1,200 or more and 10,000 or less in one molecule It is a copolymer, The polylactic acid-type resin film in any one of Claims 1-4 characterized by the above-mentioned.