JP2008248163A - Polylactic acid film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polylactic acid film having excellent flatness and few surface defects and little thickness unevenness. <P>SOLUTION: The polylactic acid film contains 0.001-5 wt.% of a film-forming improver and satisfies requirements of (1) surface nature: the number of pin-like defect observed by visual observation in a sample having 5 cm width and 50 cm length of ≤1 and (2) thickness unevenness: the thickness variation ▵R μm when the thickness of a sample with 50 cm sample length (length direction) is measured by a continuous thickness meter (electronic micrometer) is ≤7% average thickness R μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polylactic acid film having good flatness, thickness uniformity and surface property, and a production method having good productivity. More specifically, it includes a polylactic acid film containing a film-formability improving agent and an efficient method for producing the film by an electrostatic adhesion method.

  The aliphatic polyester or aromatic polyester film containing polylactic acid extrudes a molten polymer into a film shape, and then cools it on a rotating cooling drum (hereinafter sometimes referred to as a cooling drum) to form a solid unstretched film. A method of casting and stretching the unstretched film in a uniaxial direction or a biaxial direction as necessary to obtain a uniaxially stretched film or a biaxially stretched film is employed.

  When cooling on the cooling drum, if the cooling is not uniform, inconveniences such as film irregularities and uneven thickness may occur. In order to prevent this, it is necessary to make the molten film and the cooling drum adhere uniformly.

  In the aromatic polyester film, as a method for uniformly adhering the molten film to the cooling drum, a wire-like electrode is provided between the die and the cooling drum, and an electrostatic charge is applied to the molten film mainly by glow discharge and corona discharge. A casting method (hereinafter sometimes referred to as an electrostatic casting method) (Patent Document 1) is well known.

  However, even with electrostatic casting, polymers such as polylactic acid with a high volume resistivity and high melt viscosity decrease the electrostatic adhesion between the cooling drum and the film, and air is entrained between the cooling drum and the film so that the film surface However, the problems of foam defects, unevenness and thickness uniformity are not sufficiently solved.

  In particular, when the peripheral speed of the cooling drum is increased to improve film productivity, the adhesion effect of the electrostatic casting method is reduced, and air is trapped between the cooling drum and the molten film to cause bubble defects on the film surface. Problems that are likely to occur become significant.

  In aromatic polyester films, acetic acid is used as a film-formability improver to overcome the problem of reduced electrostatic adhesion and improve the film-forming speed to produce a high-efficiency, flat and uniform film with few surface defects. An ionic compound such as lithium and other alkali metals and alkaline earth metal compounds is contained in an amount of 0.005 to 5% by weight, and a method for improving electrostatic adhesion has been proposed and a desired effect has been obtained (Patent Document) 2).

  However, in polylactic acid, when an alkali metal or alkaline earth metal compound is contained, depolymerization of polylactic acid is accelerated at the time of melting, and there is a serious defect that the polymer decomposes. Therefore, these agents are added to the polylactic acid film. It is judged impossible to apply.

An effective method for producing a polylactic acid film having good surface properties and high thickness uniformity has not yet been proposed, and the appearance of polylactic acid films having good surface properties and high thickness uniformity has been struggling.
Specifically, there is an urgent need for proposals for improving electrostatic adhesion that replaces the addition of alkali metals and alkaline earth metals.

Japanese Examined Patent Publication No. 37-6142 Japanese Patent Publication No.53-40231

  An object of the present invention is to provide a polylactic acid fill having good flatness and thickness uniformity and improved surface defects. Another object of the present invention is to provide an efficient method for producing a polylactic acid film having good flatness and thickness uniformity and improved surface defects.

  As a result of intensive studies in view of the above-described conventional techniques, the present inventors have completed the present invention.

４．ポリ乳酸をダイよりフィルム状に押し出し、ダイ下でフィルム状溶融ポリ乳酸と冷却ドラムとの接点近傍にもうけられた電極から静電荷を該フィルム状溶融ポリ乳酸の片面に付与し、回転冷却ドラムの表面に密着させ、急冷固化させる工程を含む１から３のいずれかに記載のポリ乳酸フィルムの製造方法。
５．フィルム状溶融ポリ乳酸と冷却ドラムとの接点近傍にもうけられた電極との間に静電密着を起こす程度の電圧を印加することを特徴とする４に記載のポリ乳酸フィルムの製造方法。
６．電極がワイヤー状またはナイフ状である４または５に記載のポリ乳酸フィルムの製造方法。
７．高温空気流を該電極及びその近傍に吹き付け、電極上部に排気ノズルを設け強制排気する４から６のいずれかに記載のポリ乳酸フィルムの製造方法。
８．ポリ乳酸がポリＬ‐乳酸またはポリＤ‐乳酸を主成分とする４から７のいずれかに記載のポリ乳酸フィルムの製造方法。
９．一軸または二軸延伸してなり、さらにその後、示差走査熱量計（ＤＳＣ）測定による１９０℃以下の融点をＴｍｈとするときに融点（Ｔｍｈ−５０）から（Ｔｍｈ−５）℃で熱処理する８に記載のポリ乳酸フィルムの製造方法。
１０．Ｄ‐乳酸単位を主成分とし、Ｄ‐乳酸以外の共重合単位を０〜１０モル％含有する結晶性ポリ乳酸（Ｂ）と、Ｌ‐乳酸単位を主成分としＬ‐乳酸以外の共重合単位を０〜１０モル％含有する結晶性ポリ乳酸（Ｃ）とを重量比（Ｂ／Ｃ）＝１０／９０〜９０／１０で溶融熱処理してなるポリ乳酸（Ａ）よりなり、ステレオ化度（Ｓ）が８０％から１００％である１から３のいずれかに記載のポリ乳酸フィルム。
１１．一軸または二軸延伸してなり、さらにその後、示差走査熱量計（ＤＳＣ）測定による１９０℃以上の融点をＴｍｓｃとするとき、（Ｔｍｃｓ−５０）から（Ｔｍｃｓ−５）℃で熱処理する１０に記載のポリ乳酸フィルムの製造方法。 That is, the object of the present invention is to
1. A polylactic acid film satisfying the following requirements.
(1) Surface property: 1 or less pin-like defects that can be visually observed in a sample having a width of 5 cm and a length of 50 cm.
(2) Thickness variation: The thickness variation value ΔRμm when the thickness of the sample is 50 cm (longitudinal direction) is measured with a continuous thickness meter (electronic micrometer) is within 7% of the average thickness Rμm.
2. 2. The polylactic acid film according to 1, wherein the film formability improver is a sulfonic acid quaternary phosphonium salt.
3. Either 1 or 2, wherein the sulfonic acid quaternary phosphonium salt is at least one selected from the group consisting of compounds represented by formula (I) or (II) (hereinafter sometimes abbreviated as specific phosphonium salts). The polylactic acid film described in 1.

4). Polylactic acid is extruded into a film form from a die, and an electrostatic charge is applied to one side of the film-like molten polylactic acid from an electrode provided near the contact point between the film-like molten polylactic acid and the cooling drum under the die. 4. The method for producing a polylactic acid film according to any one of 1 to 3, comprising a step of bringing the surface into close contact and rapid cooling and solidification.
5. 5. The method for producing a polylactic acid film according to 4, wherein a voltage that causes electrostatic adhesion is applied between the film-like molten polylactic acid and an electrode provided in the vicinity of the contact point between the cooling drum and the film.
6). 6. The method for producing a polylactic acid film according to 4 or 5, wherein the electrode has a wire shape or a knife shape.
7). The method for producing a polylactic acid film according to any one of 4 to 6, wherein a high-temperature air stream is blown to the electrode and the vicinity thereof, and an exhaust nozzle is provided above the electrode to forcibly exhaust.
8). 8. The method for producing a polylactic acid film according to any one of 4 to 7, wherein the polylactic acid is composed mainly of poly L-lactic acid or poly D-lactic acid.
9. It is uniaxially or biaxially stretched, and then heat-treated at a melting point (Tmh-50) to (Tmh-5) ° C. 8 when the melting point of 190 ° C. or less is Tmh as measured by differential scanning calorimetry (DSC). The manufacturing method of the polylactic acid film of description.
10. Crystalline polylactic acid (B) containing a D-lactic acid unit as a main component and a copolymer unit other than D-lactic acid in an amount of 0 to 10 mol%, and a copolymer unit other than L-lactic acid as a main component Of polylactic acid (A) obtained by subjecting a crystalline polylactic acid (C) containing 0 to 10 mol% to a melt heat treatment at a weight ratio (B / C) = 10/90 to 90/10, The polylactic acid film according to any one of 1 to 3, wherein S) is 80% to 100%.
11. 10. The heat treatment is carried out at 10 ° C. from (Tmcs-50) to (Tmcs-5) when the melting point of 190 ° C. or higher measured by differential scanning calorimetry (DSC) is defined as Tmsc. Of producing a polylactic acid film.

  The polylactic acid film of the present invention is a polylactic acid film with little flatness, surface defects, and thickness unevenness, and the polylactic acid film of the present invention can be industrially produced with high efficiency.

The present invention is described in detail below.
The polylactic acid film of the present invention is a polylactic acid film containing 0.001 to 5 wt% of a film formability improver and satisfying the following requirements.
(1) Surface property: 1 or less pin-like defects that can be visually observed in a sample having a width of 5 cm and a length of 50 cm.
(2) Thickness variation: The thickness variation value ΔRμm when the thickness of the sample is 50 cm (longitudinal direction) is measured with a continuous thickness meter (electronic micrometer) is within 7% of the average thickness Rμm.
Control of surface properties and thickness spots is an indispensable condition for film applications. By having such surface properties and thickness uniformity, polylactic acid films can be developed for a wide range of applications.

More preferably (1) Surface property: 1 or less pin-like defects that can be visually observed in a sample having a width of 5 cm and a length of 3 m.
(2) Thickness variation: The thickness variation value ΔRμm when the thickness of a sample length of 3 m (longitudinal direction) is measured with a continuous thickness meter (electronic micrometer) is within 7% of the average thickness Rμm.
Range.

  The specific film-formability improver of the present invention is a film-formability improver by melt casting of polylactic acid, and more specifically, film-formability improvement that improves the adhesion of the casting film to the cooling roll during melt casting. It is an agent.

  Applying the film-formability improver in the electrostatic adhesion method to poly (D-lactic acid), poly (L-lactic acid) or poly (D-lactic acid component) and poly (L-lactic acid component) melted and heat-treated polylactic acid (A) composition A polylactic acid (A) composition obtained by melting and heat-treating poly-D-lactic acid, poly-L-lactic acid, or poly-D-lactic acid component and poly-L-lactic acid component with the above surface properties and thickness uniformity. A film can be suitably realized.

The film forming property improving agent in the electrostatic adhesion method in the present invention is preferably selected from sulfonic acid quaternary phosphonium salts.
As described above, various agents have been proposed for aromatic polyester fills such as polyethylene terephthalate. However, polylactic acid films have sulfonic acid quaternary as a film-formability improver due to the instability at the time of melting of the starting polymer. Phosphonium salts are particularly preferably applied.

The application amount of the film-forming property improving agent of the present invention is essential to contain 0.001 to 1 wt% based on polylactic acid.
If this ratio is less than 0.001 wt%, the adhesion between the polylactic acid film and the cooling drum becomes insufficient, and the object of the present invention cannot be achieved.

Moreover, when this ratio exceeds 1 wt%, the dispersibility of the sulfonic acid quaternary phosphonium salt in the polylactic acid is deteriorated, and fish eyes are generated in the film, or when the sulfonic acid quaternary phosphonium salt is melt-cast, This is because thermal decomposition and thermal decomposition of polylactic acid become prominent and coloring of the film may become remarkable.
The content of the sulfonic acid quaternary phosphonium salt is preferably 0.003 to 0.5 wt%, more preferably 0.005 to 0.1 wt%.

  By applying a sulfonic acid quaternary phosphonium salt in such a quantitative ratio to polylactic acid, the volume resistivity at the time of melting of polylactic acid is reduced, so that the application of an electrostatic charge to the polylactic acid film is sufficient, and the film It is judged that the adhesion between the cooling drum and the cooling drum is good.

The volume specific resistance value in the molten state of polylactic acid fluoride containing a sulfonic acid quaternary phosphonium salt is 0.5 × 10 ⁹ Ω. It is preferable that it is cm or less. When the volume resistivity is in this range, electrostatic application to the film is strong during casting, and the adhesion between the film and the cooling drum is further improved.
As a result, the flatness and thickness uniformity of the film become good, there are no surface defects such as pin-like defects, and the hue is also good.

  As the sulfonic acid quaternary phosphonium salt, for example, a compound represented by the formula (I) and a compound represented by the formula (II) can be preferably used.

In formula (I), X ¹ and X ² are the same or different hydrogen atoms or ester-forming functional groups. Examples of the ester-forming functional group include a carboxyl group, an alkoxycarbonyl group, and a hydroxyl group. However, X ¹ and X ² are not simultaneously hydrogen atoms.

In formulas (I) and (II), R ¹ to R ⁸ are monovalent hydrocarbon groups having 1 to 18 carbon atoms which may be the same or different, and are alkyl groups having 1 to 18 carbon atoms, and 7 to 12 carbon atoms. And an aryl group having 6 to 12 carbon atoms.

  The alkyl group having 1 to 18 carbon atoms may be linear or branched. Specifically, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, t-butyl group, n-pentyl group, n-hexyl group, Examples thereof include an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-pentadecyl group, and an n-octadecyl group.

  Examples of the aralkyl group having 7 to 12 carbon atoms include benzyl group, 2-methylbenzyl group, 4-methylbenzyl group, 2,4-dimethylbenzyl group, 4-ethylbenzyl group and the like.

  Examples of the aryl group having 6 to 12 carbon atoms include phenyl group, tolyl group, xylyl group, 2-methylphenyl group, 4-methylphenyl group, 2,4-dimethylphenyl group, naphthyl group, and biphenyl group. it can.

m and n are 1 or 2. A ¹ is an (n + 2) -valent, that is, a trivalent or tetravalent aliphatic group or aromatic group having 2 to 18 carbon atoms. Specific examples of A ¹ will be clear from the specific examples of the compound of the formula (I) described below.

  Specific examples of the quaternary phosphonium cation represented by the formula (II) include, for example, tetramethylphosphonium, tetraethylphosphonium, tetrabutylphosphonium, trimethylethylphosphonium, tributylmethylphosphonium, tributylethylphosphonium, trioctylmethylphosphonium, trimethylbutyl. Aliphatic phosphoniums such as phosphonium, trimethyloctylphosphonium, trimethyllaurylphosphonium, trimethylstearylphosphonium, triethylbutylphosphonium, triethyloctylphosphonium, tributyloctylphosphonium; trietriphenylmethylphosphonium, triphenylethylphosphonium, triphenylbenzylphosphonium, tributylbenzyl Phosphonium, tetraphenyl And aromatic phosphonium such as Suhoniumu.

  Furthermore, tetrahydroxymethylphosphonium, tris (2-cyanoethyl) methylphosphonium, tris (2-cyanoethyl) ethylphosphonium, tris (2-cyanoethyl) benzylphosphonium, tris (3-hydroxypropyl) methylphosphonium, tris (3-hydroxypropyl) ) Phosphonium cations having substituents such as benzylphosphonium, trimethyl (2-hydroxyethyl) phosphonium, tributyl (2-hydroxyethyl) phosphonium can also be used.

  As the sulfonic acid quaternary phosphonium salt represented by the formula (I), for example, 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid ethyltributylphosphonium salt, 3,5-dicarboxylic acid salt, Carboxybenzenesulfonic acid benzyltributylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid phenyltributylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid benzyltetraphenylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid ethyltriphenyl Phosphonium salt, butyl triphenylphosphonium salt of 3,5-dicarboxybenzenesulfonic acid, benzyltriphenylphosphonium salt of 3,5-dicarboxybenzenesulfonic acid, 3,5-dicarbomethoxybenze Sulfonic acid tetrabutylphosphonium salt, 3,5-dicarbomethoxybenzenesulfonic acid ethyltributylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid benzyltributylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid phenyltributylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid tetraphenylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid ethyltriphenylphosphonium salt, 3,5-dicarboxybenzenesulfonic acid butyltriphenylphosphonium salt, 3,5-dicarboxyl Benzenesulfonic acid benzyltriphenylphosphonium salt, 3-carboxybenzenesulfonic acid tetrabutylphosphonium salt, 3-carboxybenzenesulfonic acid tetraphenylphosphonium salt, -Carbomethoxybenzenesulfonic acid tetrabutylphosphonium salt, 3-carbomethoxybenzenesulfonic acid tetraphenylphosphonium salt, 3,5-bis (2-hydroxyethoxycarbonyl) benzenesulfonic acid tetrabutylphosphonium salt, 3,5-bis (2 -Hydroxyethoxycarbonyl) benzenesulfonic acid tetraphenylphosphonium salt, 3- (2-hydroxyethoxycarbonyl) benzenesulfonic acid tetrabutylphosphonium salt, 3- (2-hydroxyethoxycarbonyl) benzenesulfonic acid tetraphenylphosphonium salt, 4-hydroxy Ethoxybenzenesulfonic acid tetrabutylphosphonium salt, bisphenol A-3,3′-bis (tetrabutylphosphonium sulfonic acid salt), 2,6-dicarboxynaphthalene Examples thereof include 4-sulfonic acid tetrabutylphosphonium salt and α-tetrabutylphosphonium sulfosuccinic acid.

  Specific examples of the phosphonium cation in the formula (II) include the same as those described above for the formula (I).

  Among the sulfonic acid quaternary phosphonium salts represented by the formula (II), as the sulfonate of the compound of m = 1, for example, butyl sulfonate, octyl sulfonate, lauryl sulfonate, myristyl sulfonate, hexadecyl sulfonate, 2-ethylhexyl sulfonate, etc. Substituted phenyl sulfonates such as aliphatic sulfonates and mixtures thereof, p-tosylate, butyl phenyl sulfonate, dodecyl phenyl sulfonate, octadecyl phenyl phosphonate, dibutyl phenyl phosphonate, naphthyl sulfonate, diisopropyl naphthyl sulfonate, dibutyl naphthyl sulfonate, etc. Mention may be made of substituted naphthyl sulfonates.

  Examples of the sulfonate of the compound of m = 2 include 1,1-ethanedisulfonate, 1,2-ethanedisulfonate, phenol-2,4-disulfonate, phenol-2,5-disulfonate, and 1,2-dihydroxybenzene. 3,5-disulfonate, 1,4-dihydroxybenzene-3,5-disulfonate, 1,4-benzenedisulfonate, 2,5-dimethyl-1,3-benzenedisulfonate, 4-methyl-1, 3-benzenedisulfonate, 5-methyl-1,3-benzenedisulfonate, 5-methoxycarbonyl-1,3-benzenedisulfonate, 1,8-dihydroxyanthraquinone-2,7-disulfonate, 1,5-dihydroxy Anthraquinone-2,6-disulfonate, 1,5-dimethoxyanthraquinone-2, - disulfonate, and the like.

Of these quaternary phosphonium sulfonates, the sulfonic acid quaternary phosphonium salt represented by the formula (I) is preferably used in the above-mentioned quantitative ratio, so that the adhesion between the polylactic acid film and the cooling drum is improved.
In particular, 3,5-carboxybenzene-4-sulfonic acid tetrabutylphosphonate is preferable.

  In addition, although sulfonic acid quaternary phosphonium salt can also be used only by 1 type, in order to achieve desired objectives, such as heat resistance of a film, lubricity, and transparency, it is also a preferable usage method to use together 2 or more types. is there.

In order to apply the sulfonic acid quaternary phosphonium salt and other additives to the polylactic acid of the present invention, the agent can be blended at a stage between the start of polylactic acid polymerization and before film formation.
When the agent is added while the resin is in a molten state from the start to the end of the polymerization, the agent-containing polylactic acid can be produced by using a normal agent charging method.

  In order to add the agent once to a solid state such as pellets after melt fusion of polylactic acid, various conventionally known methods can be suitably used. For example, a method of mixing polylactic acid and a phosphoric acid ester metal salt with a tumbler, V-type blender, super mixer, nauta mixer, Banbury mixer, kneading roll, uniaxial or biaxial extruder or the like is appropriately used.

  Polylactic acid containing a sulfonic acid quaternary phosphonium salt and the like thus obtained can be melt-mixed and transferred to a film forming apparatus as it is or via a metering pump, etc. Then, a method of supplying to the film forming apparatus is also possible.

  The shape of the pellet is preferably one having a shape suitable for forming the pellet by various molding methods, specifically, the pellet length is 1 to 7 mm, the major axis is 3 to 5 mm, and the minor axis is 1 to 4 mm. In addition, the pellet shape is preferably one with little variation.

Furthermore, in the film of the present invention, it is preferable to apply a lubricant in polylactic acid for the purpose of improving film winding and running properties.
This lubricant may be solid or liquid at room temperature, and preferably has a melting point or softening point of 200 ° C. or lower. Specific examples of the lubricant include the following, and two or more of these may be used in combination.

Aliphatic hydrocarbons: liquid paraffin, microcrystalline wax, natural paraffin, synthetic paraffin, polyethylene wax, polypropylene wax, etc.
Higher fatty acids or metal salts thereof: stearic acid, calcium stearate, hydroxystearic acid, hydrogenated oil, sodium montanate, etc.
Fatty acid amide: stearic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, behenic acid amide, methylene bissteryl amide, etc.
Fatty acid ester: n-butyl stearate, methyl hydroxy stearate, myricyl cellotinate, higher alcohol fatty acid ester, ester wax, etc.
Fatty acid ketone: ketone wax, etc.
Aliphatic higher alcohols: lauryl alcohol, stearyl alcohol, myristyl alcohol, cetyl alcohol, etc.
Polyhydric alcohol fatty acid ester or partial ester: glycerin fatty acid ester, hydroxystearic acid triglyceride, sorbitan fatty acid ester, etc.
Nonionic surfactant: polyoxyethylene alkyl ether, polyoxyethylene phenyl ether, polyoxyethylene alkylamide, polyoxyethylene fatty acid ester, etc.
Silicone oil: linear methyl silicone oil, methylphenyl silicone oil, modified silicone oil, etc.
Fluorine-based surfactant: fluoroalkyl carboxylic acid, perfluoroalkyl carboxylic acid, monoperfluoroalkyl ethyl phosphate ester, perfluoroalkyl sulfonate, and the like.

  These lubricants may be used alone or in combination of two or more. The lubricant is applied in the range of 0.001 to 1 wt%, more preferably 0.005 to 0.5 wt% in polylactic acid.

In the film of the present invention, a lubricant can be applied in polylactic acid for the purpose of improving film winding and running properties.
Examples of such lubricants include silica produced by a dry method, silica produced by a wet method, zeolite, calcium carbonate, calcium phosphate, kaolin, kaolinite, clay, talc, titanium oxide, alumina, zirconia, aluminum hydroxide, Preferable examples include inorganic particles such as calcium oxide, graphite, carbon black, zinc oxide, silicon carbide, and tin oxide; and organic fine particles such as crosslinked acrylic resin particles, crosslinked polystyrene resin particles, melamine resin particles, and crosslinked silicone resin particles.

As the lubricant, fine particles having an average particle diameter of 0.001 to 5.0 μm are preferable, and one kind can be used, or two or more kinds can be used in combination.
These can be blended in the range of 0.01 to 0.5 wt% with respect to polylactic acid.
In addition to these agents, antioxidants, antistatic agents, colorants, pigments, fluorescent whitening agents, plasticizers, crosslinking agents, ultraviolet absorbers, and other resins can be added as necessary.

  The polylactic acid film of the present invention is cooled by applying the sulfonic acid quaternary phosphonium salt and, if desired, the above-described lubricant, extruding a molten film of polylactic acid onto a cooling drum, and bringing the film into close contact with a rotating cooling drum. Manufactured by doing. At this time, since polylactic acid flum contains 0.001 to 1 wt% of sulfonic acid quaternary phosphonium salt, it is possible to easily apply a non-contact electric charge from the electrode to the flum melting surface in the vicinity of the cooling of the flum. So that the film can be brought into close contact with the rotating cooling drum.

For example, a polylactic acid composition containing the sulfonic acid quaternary phosphonium salt and, if desired, the above-mentioned lubricant is supplied to an extruder and melted to a temperature not lower than the polymer melting point and not higher than 300 ° C. The film is discharged in the form of a film, and an unstretched film can be produced by cooling and solidifying with a cooling drum while applying an electrostatic charge to the film from the electrode.
The electrode for applying an electrostatic value to the film preferably has a wire shape or a knife shape.

  It is preferable that the surface material of the electrode is platinum. That is, when film formation is continued for a long time, there is a concern that impurities that sublimate from the film may adhere to the electrode surface or the electrode surface may be deteriorated, reducing the ability to apply static electricity. It is possible to prevent adhesion of impurities by spraying in the vicinity and installing an exhaust nozzle above the electrode.

Moreover, the said problem can be prevented more efficiently by using platinum as an electrode surface material and keeping a discharge electrode at 170-350 degreeC.
The polylactic acid supplied to the film forming machine is preferably dried before supplying the film forming machine in order to suppress decomposition at the time of melting. The water content is particularly preferably 100 ppm or less.

  The unstretched film can be further stretched in a uniaxial direction or a biaxial direction as necessary to obtain a uniaxially stretched film or a biaxially stretched film. In order to obtain such a uniaxially stretched film or a biaxially stretched film, the unstretched film is heated from a temperature at which the unstretched film can be stretched, that is, a glass transition temperature of polylactic acid (hereinafter sometimes referred to as Tg) to a temperature of (Tg + 80) ° C. And at least uniaxially stretched.

A draw ratio is selected in the range of 2 to 12 times for a uniaxially stretched film and 5 to 50 times in terms of a stretched area ratio for a biaxially stretched film.
The axially stretched film is produced by, for example, a longitudinal-lateral sequential stretching method in which an unstretched film is first stretched in the longitudinal direction and then stretched in the transverse direction, and a simultaneous axial stretching method in which the longitudinal direction and the transverse direction are simultaneously stretched. be able to.

This biaxially stretched film can be further restretched in the longitudinal direction or the uniaxial direction of the transverse direction, or in the biaxial direction of the longitudinal direction and the transverse direction to form a biaxially restretched film.
When the polylactic acid is poly D-lactic acid or poly L-lactic acid, the above uniaxially stretched film or biaxially stretched film is heat-treated at a temperature below Tmh and cooled to room temperature when the crystal melting temperature of polylactic acid is Tmh. Thus, a uniaxially stretched heat-treated film or a biaxially stretched heat-treated film can be obtained.

  Preferably, by setting the heat treatment temperature from (Tmh-5) to (Tmh-50) ° C., the film is hardly broken, the heat setting effect is sufficiently high, and a film having good dimensional stability can be obtained.

  A uniaxially stretched film or a biaxially stretched film of polylactic acid (A) is heat-treated at a temperature below Tmsc and cooled to room temperature when the complex phase crystal melting point of polylactic acid (A) is Tmsc. Alternatively, it can be a biaxially stretched heat treatment film.

  Preferably, by setting the heat treatment temperature from (Tmsc-5) to (Tmsc-50) ° C., the film is hardly broken and the heat setting effect is sufficiently high, and a film having good dimensional stability can be obtained.

  The uniaxially stretched film or biaxially stretched film thus obtained is subjected to surface activation treatment, for example, plasma treatment, amine treatment, corona treatment, and the like, if desired, to improve wettability, printability and the like. Is also possible.

  The poly-D-lactic acid or poly-L-lactic acid according to the present invention is a copolymer containing poly-lactic acid and other copolymerization components, each of which is composed mainly of lactic acid units. Examples of the compound include polylactic acid, and polylactic acid is preferably substantially composed of only lactic acid units.

From the viewpoint of film properties such as crystallinity and heat resistance in this poly-D-lactic acid and poly-L-lactic acid, the main monomer units, D-lactic acid units and L-lactic acid units, are 90 to 100 mol%, preferably 95 A range of -100 mol%, more preferably 98-100 mol% is selected.
That is, the copolymer component unit other than the main constituent components is in the range of 0 to 10 mol%, preferably 0 to 5 mol%, more preferably 0 to 2 mol%.

The polylactic acid has crystallinity, and its melting point is preferably 150 ° C. to 190 ° C., and more preferably 160 ° C. to 190 ° C. or less.
If the crystal melting point is within this range, the crystallinity of the film made of the polymer can be increased and the heat resistance can be increased, and the stereocomplex phase of the polylactic acid (A) composition containing the component (complex phase and the following description). This is because it is suitable for promoting the formation of the crystallinity and heat resistance.

  The poly D-lactic acid and poly L-lactic acid used in the present invention are preferably selected from the viewpoint of achieving both film formability and mechanical properties of the film, and more preferably having a weight average molecular weight in the range of 80,000 to 500,000. Is selected from the range of 100,000 to 250,000, more preferably 140,000 to 250,000.

  The component that can be copolymerized is not particularly limited. For example, hydroxycarboxylic acids such as glycolic acid, caprolactone, butyrolactone, propiolactone, ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-propanediol, 1,5-propanediol, hexanediol, octanediol, decanediol, dodecanediol, aliphatic diols having 2 to 30 carbon atoms, succinic acid, maleic acid, adipic acid, 2 carbon atoms To 30 or more monomers selected from aromatic diols such as aliphatic dicarboxylic acid, terephthalic acid, isophthalic acid, hydroxybenzoic acid, hydroquinone, and aromatic dicarboxylic acid.

The method for producing poly-D-lactic acid and / or poly-L-lactic acid used in the present invention is not particularly limited, and conventionally known methods can be used.
For example, it can be produced by a method in which each lactic acid is directly dehydrated and condensed, or a method in which each lactic acid is once subjected to dehydration cyclization to lactide and then ring-opening polymerization. Any catalyst can be used as the catalyst used in these production methods as long as the poly L-lactic acid component and the poly D-lactic acid component can be polymerized so as to have predetermined characteristics, but tin octylate, Examples include divalent tin compounds such as tin chloride and tin alkoxides, tetravalent tin compounds such as tin oxide, butyltin oxide, and ethyltin oxide, metal tin, zinc compounds, aluminum compounds, calcium compounds, and lanthanide compounds. .

The polylactic acid (A) composition comprising the poly D-lactic acid component and the poly L-lactic acid component of the present invention is a low-temperature crystal melt phase (hereinafter abbreviated as a homo phase) comprising the poly L-lactic acid and the poly D-lactic acid alone. ))) And a high-temperature crystal melting phase (hereinafter sometimes abbreviated as a complex phase) made of stereocomplex polylactic acid, and the low-temperature crystal melting heat measured with a differential scanning calorimeter is ΔHm1, high-temperature crystal melting. When the heat is ΔHm2, it is preferably a polylactic acid having a stereogenicity represented by the formula (3) of 80% or more.
[Equation 1]
S = ΔHm2 / (ΔHm1 + ΔHm2) × 100 (3)
Such polylactic acid (A) can be obtained by subjecting the above-mentioned poly L-lactic acid and poly D-lactic acid to melt heat treatment at 220 to 300 ° C. in the range of 10/90 to 90/10 by weight.

For the mixing ratio of poly-D-lactic acid and poly-L-lactic acid, the above weight ratio is preferably in the range of 30/70 to 70/30, more preferably in the range of 40/60 to 60/40, in order to increase the degree of stereoization. Is selected and is preferably as close to 50/50 as possible.
The melting heat treatment temperature is selected in the range of 230 to 300 ° C., more preferably 230 to 280 ° C., considering the stability at the time of melting polylactic acid.
Alternatively, a stereoblock polylactic acid in which a poly L-lactic acid segment and a poly D-lactic acid segment are bonded at the above-mentioned quantitative ratio can also be suitably used.

Stereoblock polylactic acid is a block polymer in which a poly-L-lactic acid segment and a poly-D-lactic acid segment are bonded in the molecule. Such a block polymer is, for example, a method of producing by sequential ring-opening polymerization or a method of polymerizing poly-L-lactic acid and poly-D-lactic acid and then binding them with a chain exchange reaction or a chain extender. The above-mentioned basic methods such as a method of polymerizing poly-L-lactic acid and poly-D-lactic acid, blending and then solid-phase polymerizing to extend the chain, a method of producing from racemic lactide using a stereoselective ring-opening polymerization catalyst, etc. Any block copolymer having a structure can be used regardless of the production method. However, it is more preferable from the viewpoint of ease of production to use a high-melting stereoblock polymer obtained by sequential ring-opening polymerization and a polymer obtained by a solid phase polymerization method.
The melt heat treatment method is not particularly limited, but a melt kneading method, more preferably a melt kneading method under shearing conditions is preferred.

  As the apparatus used for melt kneading, a conventionally known batch type or continuous type melt mixing apparatus is preferably used. For example, melt-stirred tanks, single- and twin-screw extruders, kneaders, non-shaft vertical stirring tanks, Sumitomo Heavy Industries Viola racks, Mitsubishi Heavy Industries N-SCR, Hitachi glass blades, lattice blades or Kenix type, or Sulzer type SMLX type static mixer equipped pipe type polymerization tank can be used, but finisher, N-SCR, twin screw extrusion ruder, etc. which are self-cleaning type polymerization equipment in terms of productivity, polylactic acid quality, especially color tone are suitable used.

  Polylactic acid (A) contains a teleo complex crystal. The content rate of the stereocomplex crystal is preferably 80 to 100%, more preferably 95 to 100% in terms of the degree of stereogenicity (S). The crystal melting point of the complex phase is in the range of 195 to 250 ° C, more preferably in the range of 200 to 220 ° C. The melting enthalpy is 20 J / g or more, preferably 30 J / g or more.

  Specifically, in the differential scanning calorimeter (DSC) measurement, the ratio of the melting peak at 195 ° C. or higher in the melting peak in the temperature rising process is 90% or higher, and the melting point is in the range of 195 to 250 ° C. It is preferable that the melting enthalpy is 20 J / g or more.

The poly D-lactic acid component and D-lactic acid component used in the present invention preferably have a weight average molecular weight decrease of 20% or less when melted at 260 ° C. If the molecular weight is drastically reduced at high temperature, not only film formation becomes difficult, but physical properties of the obtained film are lowered, which is not preferable.
For the poly-D-lactic acid component and the poly-L-lactic acid component, it is preferable to remove the polymerization catalyst used in the polymerization by a conventionally known method, for example, with a solvent, or to deactivate the catalytic activity.

In order to inactivate the catalyst activity, an agent that deactivates the polymerization activity of the polymerization catalyst, called a catalyst deactivator, that is, a chelate coordination having an imino group and capable of coordinating with a specific metal-based polymerization catalyst Including organic ligands consisting of a group of children, phosphorus oxoacid, phosphorus oxoacid ester and formula (4), organic phosphorus oxoacid compound group represented by formula, cyclic and ultra region metaphosphate compounds represented by formula (5) It is also an effective means to lose the catalytic activity by blending at least one agent selected from metaphosphoric acid compounds at 0.3 to 20 equivalents per equivalent of metal element in the catalyst at the end of the polymerization. .
_{X 1 -P (= O) m} (OH) n (OX 2) 2-n (4)
(In the formula, m is 0 or 1, n is 1 or 2 X ₁ , X ₂ each independently represents a hydrocarbon group optionally having a substituent having 1 to 20 carbon atoms.)

該失活剤の使用量はさらにこのましくは前記基準で０．４から１５当量、特に好ましくは０．５から１０当量の範囲である。

The amount of the deactivator used is more preferably in the range of 0.4 to 15 equivalents, particularly preferably 0.5 to 10 equivalents based on the above criteria.

  It is preferable to add a specific additive to the polylactic acid (A) composition used in the present invention in order to improve the degree of stereoification. As such an additive, a phosphoric acid ester metal salt represented by the following formula can be given as a preferred example.

  These metal salts are preferably used in an amount of 10 ppm to 2 wt%, more preferably 50 ppm to 0.5 wt%, and still more preferably 100 ppm to 0.3 wt% with respect to the polylactic acid component. If the amount is too small, the effect of improving the degree of stereoization is small.

  The polylactic acid film having good flatness and thickness uniformity and having no surface defects such as pin-like defects of the present invention includes a packaging film, a film for a capacitor (for example, a film having a thickness of 3 μm or less), a film for a printer ribbon (for example, a meat) Useful for heat sensitive stencil printing film, magnetic recording film (for example, for QIC tape: 1/4 inch tape for computer recording), and Montglare film (for example, film having a thickness of 50 μm or less). .

Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited thereto. In the examples, “parts” means parts by weight, and the molecular weight of polylactic acid means a weight average molecular weight.
The weight average molecular weight, melting point, crystal melting peak, stereogenicity, film, polymer volume resistivity, electrostatic castability, and film thickness uniformity of polylactic acid were evaluated by the following methods.

(1) Weight average molecular weight (Mw) and number average molecular weight (Mn):
It calculated | required by the comparison with the polystyrene standard sample by the gel permeation chromatography (GPC).
The GPC measuring instrument was as follows, using chloroform eluent, flowing at a column temperature of 40 ° C. and a flow rate of 1.0 ml / min, and injecting 10 μl of a sample having a concentration of 1 mg / ml (chloroform containing 1% hexafluoroisopropanol).
Detector: Differential refractometer RID-6A manufactured by Shimadzu Corporation
Pump: LC-9A manufactured by Shimadzu Corporation
Column: Tosoh Corporation TSKgelG3000HXL, TSKgelG4000HXL, TSKgelG5000HXL and TSKguardcocumHXL-L connected in series

(2) Crystal melting point, heat of crystal fusion (ΔHm) and degree of stereoification (S):
This was measured by a DCS7 differential scanning calorimeter (DSC) manufactured by PerkinElmer Co., Ltd. A 10 mg sample was heated from 30 ° C. to 250 ° C. at a rate of temperature increase of 20 ° C./min in a 1st RUN under a nitrogen atmosphere, crystallization temperature (Tcc), crystallization enthalpy (ΔHcc), crystal melting point (Tm) The crystal melting and melting heat (ΔHm) was measured.
The degree of stereolation (S) was determined by the following formula for polylactic acid from the homophase crystal melting heat (ΔHmh) of 190 ° C. or lower and the high-temperature crystal melting heat (ΔHmsc) of 190 ° C. or higher.
[Equation 2]
S = ΔHmsc / (ΔHmsc + ΔHmh) × 100 (3)
Further, after holding at 250 ° C. for 5 minutes, the temperature is lowered from 250 ° C. to 30 ° C. at a rate of temperature drop of 5 ° C./min, crystallization enthalpy (ΔHcc) crystallization start temperature (Tcci), crystallization peak temperature (Tccp), The crystallization end temperature (Tccf) was measured.

(3) Volume resistivity (Z):
A film having a thickness of about 150 μm was inserted in close contact with the electrode at a parallel gap of 150 μm between a cylindrical lower electrode having a diameter of 20 cm and an upper electrode having a diameter of 5.6 cm and a thickness of 0.2 cm, and the electrode was inserted into the film. Heating to (melting point +30) ° C., applying an AC voltage of 100 V, measuring the current flowing through the film, and obtaining by the following formula.
Z represents a volume resistivity, E represents an applied voltage, I represents a current, and d represents a gap between electrodes.
[Equation 3]
Z = (E / I) × (S / d) (8)

(4) Determination of film surface properties and thickness uniformity:
Surface property: The presence or absence of pin-like defects was determined by visual judgment of a sample having a width of 5 cm and a length of 50 cm.
Thickness uniformity: The thickness of a sample length of 50 cm (longitudinal direction) was measured with an electronic micrometer, and the thickness fluctuation value (ΔR) was within 7% of the average thickness R μm.

(5) Unstretched film flatness:
When an unstretched film material having a width of 1 m and a length of 2 m and a thickness of 200 μm was spread on a flat artificial leather and both ends were lightly pulled, the thickness unevenness was determined by visual judgment of unevenness generated on the film.
When almost unevenness was not recognized, it was determined to be acceptable (◯), and when unevenness was observed, it was determined to be unacceptable (x).

(6) Electrostatic castability:
When polylactic acid is melt-extruded into a film at a resin temperature of 260 ° C., a film having a thickness of 210 μm is applied by applying a voltage of 7000 V between the cooling drum and a wire electrode placed at the top of the extruded film at the top of the extruded film. When casting, the maximum speed of the cooling drum that can stably form a film with good flatness and thickness uniformity without causing pin-shaped defects was determined, and the maximum speed of the cooling drum was determined as follows. .
When the maximum drum speed was 50 m / min or more, it was judged as good (◎). When the maximum drum speed was 20 m / min to 50 m / min, it was judged as acceptable (◯), and when it was less than 20 m / min, it was judged as unfit for industrial production and rejected (x).

(7) Melt stability (%):
The retention rate of reduced viscosity after holding the sample at 260 ° C. for 10 minutes in a nitrogen atmosphere was measured. When a polylactic acid resin molded product was produced, if the melt stability was 80% or more, ordinary injection molding, extrusion molding, or other melt molding could be performed without any problem, and it was determined that the melt stability was acceptable.
The reduced viscosity (ηsp / c) was measured by dissolving 1.2 mg of a sample in 100 ml of [tetrachloroethane / phenol = (6/4) wt mixed solvent] at 35 ° C. using an Ubbelohde viscosity tube.

[Production Example 1] Production example of poly L-lactic acid (PLLA-1):
After substituting a full-zone blade equipped vertical stirring tank (40 L) equipped with vacuum piping, nitrogen gas piping, catalyst, lactide addition piping, alcohol initiator addition piping with nitrogen, 30 kg of L-lactide with an optical purity of more than 99.8%, Stearyl alcohol 0.69 kg (0.023 mol / kg-LD) and tin octylate 6.14 g (5.05 × 10 ⁻⁴ mol / 1 kg-LD) were charged and the pressure was increased to 150 under an atmosphere of nitrogen pressure 106.4 kPa. When the temperature was raised and the contents were dissolved, stirring was started, and the internal temperature was further raised to 190 ° C. Cooling was started after the internal temperature exceeded 180 ° C. and the reaction started, and the internal temperature was maintained from 185 ° C. to 190 ° C., and the reaction was continued for 2 hours.

  Next, the internal pressure was increased from 2 atmospheres to 5 atmospheres, and the contents were fed to a stirring vessel equipped with a Max Blend blade. While stirring, the reaction was performed at a nitrogen pressure of 106.4 kPa and an internal temperature of 200 ° C. to 210 ° C. for 2 hours, and then the stirring was stopped. The internal pressure was reduced to 13.3 kPa and the amount of lactide was adjusted for 20 minutes. Thereafter, the internal pressure was increased from 2 to 3 atm by nitrogen pressure, and the prepolymer was extruded into a chip cutter to pelletize a prepolymer having a weight average molecular weight of 650,000 and a molecular weight dispersion of 1.5.

After the batch reaction was carried out three times, the prepolymer was fed at a rate of 16 kg / hr to the first non-axial vertical stirring blade polymerization apparatus having a volume of 60 L, catalyst, L-lactide 16 kg / hr, and tin octylate catalyst. 5.05 × 10 ⁻⁴ mol / 1 kg-LD per kg of lactide was sent, polymerized at 200 to 210 ° C. for 2.5 hours of residence time, and transferred to the second non-axial vertical stirring blade equipped polymerization apparatus At the entrance, 1.05 mol of phosphoric acid as a deactivator was added per 1 mol of catalyst, and the inside pressure was 1.33 kPa, the residence time was 0.5 hours, and then the lactide was reduced. did.
The polyL-lactic acid resin subjected to the lactide reduction treatment had a weight average molecular weight of 205,000, a melting point (Tm) of 168 ° C., a crystallization point (Tc) of 122 ° C., and a lactide content of 0.005 wt%.

[Production Example 2] Production example of poly-D-lactic acid (PDLA-1):
A similar synthetic experiment was carried out using D-lactide having an optical purity of more than 99.8%, and a polylactic acid plan was produced according to Production Example 1. Poly D-lactic acid had a weight average molecular weight of 201,000, a melting point (Tm) of 168 ° C., a crystallization point (Tc) of 122 ° C., and a lactide content of 0.005 wt%.

[Production Example 3] Production example of poly L-lactic acid (PLLA-2):
At the time of preparation in Production Example 1, 0.12 kg of spherical silica (average particle size 0.6 μm) was additionally added, and polymerization was carried out in the same manner as described below to obtain a weight average molecular weight of 204,000, melting point (Tm) of 168 ° C., crystallization point ( Tc) 122 ° C., true spherical silica content 0.2 wt%, Poly L-lactic acid having a lactide content of 0.005 wt% was obtained.

[Production Example 4] Production example of poly-D-lactic acid (PDLA-2):
At the time of preparation in Production Example 2, 0.12 kg of spherical silica (average particle size 0.6 μm) was additionally added, and polymerization was carried out in the same manner as described below to obtain a weight average molecular weight of 202,000, melting point (Tm) of 168 ° C., crystallization point ( Tc) 122 ° C., true spherical silica content 0.2 wt%, Poly D-lactic acid having a lactide content of 0.005 wt% was obtained.

[Example 1] Film formation of a phosphonium salt-containing composition:
A twin screw extruder after mixing 0.5 parts by weight of tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate with 100 parts by weight of poly L-lactic acid produced in Production Example 1 and dried at 110 ° C. for 5 hours with a Henschel mixer A composition having a melt stability of 90% obtained by melting and kneading in a melt was extruded into a film of 210 μm at 260 ° C., and adhered and solidified to the surface of the mirror-cooled drum by electrostatic casting using a platinum-coated linear electrode.
At this time, the rotational speed of the cooling drum is gradually increased, and the maximum casting speed that can be satisfactorily produced is 50 m / min without causing a pin-like defect flatness defect or thickness uniformity defect due to poor adhesion. It was judged that the castability passed.

The composition was capable of forming a film at a polymer temperature of 240 ° C. and a castering speed of 20 m / min for 1 hour without variation in adhesion.
The unstretched film was further stretched at 120 ° C., 3.6 times in the longitudinal direction, 3.9 times in the transverse direction, and heat-set at 140 ° C. to obtain a biaxially stretched film having a thickness of 15 μm. The film passed both surface properties and thickness uniformity.

[Examples 2 to 5]
The amount of 3,5-carboxybenzenesulfonic acid tetrabutylphosphonium salt in Example 1 was changed to the value shown in Table 1, and in Examples 2 to 4, PLLA-1 was further changed to PDLA-1, which was the same as Example 1. Then, cast film forming electrostatic casting property was evaluated at 260 ° C. Table 1 shows electrostatic casting properties and melt stability.
Furthermore, an unstretched film and a stretched film were produced under the same conditions as in Example 1. The smoothness, surface property, thickness uniformity, stretched film surface property, and thickness uniformity of the unstretched film in these experiments were good.

[Comparative Examples 1-4]
In Comparative Example 1, the casting property of the composition of Example 1 to which tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate was not applied was evaluated.
The maximum casting speed without pinning was only 10 m / min.
Furthermore, an unstretched film and a stretched film were produced under the same conditions as in Example 1. The surface property and thickness uniformity of the unstretched film were unacceptable, and unevenness was observed in the smoothness, and the surface property and thickness uniformity were also unacceptable in the stretched film.

  In Comparative Examples 2 and 3, casting was carried out by changing the tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate of Example 1 to sodium acetate and potassium acetate. In Comparative Examples 2 and 3, polylactic acid was decomposed, the molecular weight was greatly reduced, and casting was difficult. Furthermore, the polylactic acid discharged from the die was colored for decomposition and was not suitable for commercialization.

In Comparative Example 4, a film was formed by changing only the amount of tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate to 3 wt%.
The yellowing of the polymer was observed, the stain on the mirror cooling roll was remarkable, the stain was transferred to the film surface, and the surface property was poor. The results are summarized in Table 1.

[Examples 6 to 13] Examination of types and amounts of sulfonic acid quaternary phosphonium salts:
Casting properties were evaluated by changing the types and amounts of polylactic acid and sulfonic acid quaternary phosphonium salt in Example 1 to the polylactic acid and sulfonic acid quaternary phosphonium salts and amounts shown in Table 2.
In these experiments, all of the electrostatic castability was acceptable (、), and the melt stability of the composition by blending the agent was as good as 90% or more. In addition, PLLA-2 and PDLA-2 were polylactic acid containing true spherical silica and had good film forming properties.
When an unstretched film and a stretched film were produced under the same conditions as in Example 1, the surface properties and thickness uniformity of all the stretched films in each experiment were acceptable.

Example 14 Polymerization Addition of Film Forming Improvement Agent:
First preaxle type agitation with a volume of 60 L of prepolymer produced in the same manner as (PLLA-1) and 3,5-dicarboxysulfonic acid tetrabutylphosphonium salt (0.1 part by weight per 100 parts by weight of the polymer) At a transfer rate of 16 kg / hr, the octylate catalyst was fed at a transfer rate of 16 kg / hr to 5.05 × 10 −4 mol / 1 kg L-LD per kg of lactide, and a residence time of 2.5 ° C. from 200 ° C. to 210 ° C. Polymerization was carried out for a period of time, transferred to a second non-axial vertical stirring blade equipped polymerization apparatus, and 1.05 mol of deactivating agent phosphoric acid per mol of catalyst was added at the inlet, internal pressure 1.33 kPa, residence time 0. After performing the lactide reduction treatment for 5 hours, it was transferred to a chip cutter with a metering pump to form a chip.
The lactide-reduced poly L-lactic acid had a weight average molecular weight of 200,000, a crystal melting point (Tmh) of 167 ° C., and a lactide content of 0.005 wt%. This composition is referred to as (PLLA-101).
The composition had a maximum casting speed at 260 ° C. of 50 m / min, no pin-like defects, a film with good thickness uniformity and smoothness, and passed electrostatic castability (（).
When an unstretched film and a stretched film were produced under the same conditions as in Example 1, the surface properties and thickness uniformity of all the stretched films in each experiment were acceptable.

[Example 15]
A similar experiment was conducted by replacing only the tetrabutylphosphonium salt of 3,5-dicarboxysulfonic acid of Example 14 with a tetrabutylphosphonium salt of dodecylbenzenesulfonic acid. This composition is referred to as (PLLA-102).
The poly L-lactic acid resin subjected to lactide reduction treatment had a weight average molecular weight of 202,000, a melting point (Tm) of 168 ° C., and a lactide content of 0.005 wt%.
The composition had a maximum casting speed of 55 m / min, no pin-like defects, a film with good thickness uniformity and smoothness, and passed electrostatic castability (静電).
When an unstretched film and a stretched film were produced under the same conditions as in Example 1, the surface properties and thickness uniformity of all the stretched films in each experiment were acceptable.

[Examples 16 and 17]
In Examples 14 and 15, the PLLA-1 prepolymer was changed to PDLA-1 prepolymer, and polymerization was performed in the same manner. The weight average molecular weights of the poly D-lactic acid subjected to the lactide reduction treatment were 205,000 and 203,000, the melting point (Tm) was 168 ° C., and the lactide content was 0.005 wt%. The compositions are referred to as (PDLA-101 and PDLA-101), respectively.
The composition had a maximum casting speed of 55 m / min, no pin-like defects, a film with good thickness uniformity and smoothness, and passed electrostatic castability (静電).
When an unstretched film and a stretched film were produced under the same conditions as in Example 1, the surface properties and thickness uniformity of all the stretched films in each experiment were acceptable.

[Example 18] Film formation of stereocomplex composition:
A mixture of PLLA-1 and PDLA-1 produced in Production Examples 1 and 2 at a weight ratio of 1/1 was dried at 120 ° C. for 5 hours, and 3,5-dicarboxybenzenesulfone was fed from the first feed port of the twin-screw extruder. Acid tetraphenylsulfonium salt (0.05 parts by weight per 100 parts by weight of the mixture) is supplied from the second supply port of the twin screw extruder and melt-kneaded at 250 ° C. (this polylactic acid (A) composition is called scPLA1). ), Melt extruded into a 210 μm film at 260 ° C., and using a platinum-coated linear electrode, in the same manner as in Example 1, was adhered and solidified on the surface of the mirror-cooled drum by the electrostatic casting method to evaluate electrostatic castability. . The melt stability of the composition was 82%.
When the rotational speed of the cooling drum was gradually increased, the maximum casting speed at which no pin-like defects or the like of the film due to poor adhesion occurred was 50 m / min, and the electrostatic casting property was acceptable.
In the same manner as in Example 1, film formation was possible at 240 ° C. and a speed of 20 m / min for 1 hour without variation in adhesion. The unstretched film having good smoothness, surface property, and thickness unevenness is further stretched at 180 ° C, 3.6 times in the longitudinal direction, 3.9 times in the transverse direction, and heat-set at 190 ° C to a thickness of 15 µm. A biaxially stretched film was obtained.
The obtained stretched film had no pin-like defects and good thickness uniformity. The film had a high-temperature phase melting peak of 223 ° C. and a stereoization rate of 95%. The results are listed in Table 4.

[Example 19]
In Example 18, 100 parts by weight of a mixture of PLLA-1 and PDLA-1 having a weight ratio of 1/1 and 0.2 part by weight of ADEKA phosphate aluminum salt (ADEKA STAB NA-71) were dried at 120 ° C. for 5 hours. From the first supply port of the twin-screw extruder, 3,5-dicarboxybenzenesulfonic acid tetraphenylsulfonium salt (0.05 parts by weight per 100 parts by weight of the mixture) and a carbodiimide compound of a carboxyl group blocking agent (the mixture) (0.5 parts by weight per 100 parts by weight) (Nisshinbo Co., Ltd. Carbodilite LA-1) was supplied from the second supply port, melt kneaded at a cylinder temperature of 230 ° C. (this composition is called scPLA2), and Example 18 In the same way, when the electrostatic castability was evaluated, it was manufactured well without causing pin-like defects in the film due to poor adhesion. Maximum casting speed that can is 50m / min, electrostatic casting property was passed ◎. The melt stability was 90%.
The stretched film produced under the same conditions as in Example 18 showed no pin-like defects and good thickness uniformity. The film had a high-temperature phase melting peak of 221 ° C. and a stereoization rate of 100%. The results are listed in Table 4.

[Comparative Example 5]
In Example 18, the electrostatic casting property was evaluated for the composition to which the sulfonic acid quaternary phosphonium salt was not added. The maximum casting speed of a film with good smoothness with no pin-like defects is only 20 m / min, the electrostatic castability is poor, and the productivity is low and there is a cost problem in the industrial examples. there were.
In the stretched film produced under the same conditions as in Example 18, 2 to 3 pin-like defects were observed in the sample, and the thickness uniformity was unacceptable. The film had a high-temperature phase melting peak of 224 ° C. and a stereoization rate of 91%.

[Comparative Example 6]
In Comparative Example 6, a polylactic acid (A) composition was produced in the same manner as in Example 19 except that 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt was not applied, and electrostatic casting properties were evaluated. The maximum casting speed of a film with good smoothness without pin-like defects is only 25 m / min, and the electrostatic castability is not acceptable x, and the productivity is low and there is a cost problem in the industrial examples. there were.
In the stretched film produced under the same conditions as in Example 18, 2 to 3 pin-like defects were observed in the sample, and the thickness uniformity was unacceptable. The film had a high-temperature phase melting peak of 224 ° C. and a stereoization rate of 100%.

[Comparative Example 7]
In Comparative Example 7, as in Example 18, except that 3,5-dicarboxybenzenesulfonic acid tetraphenylphosphonium salt was replaced with sodium acetate to produce a polylactic acid (A) composition, and the electrostatic casting property was evaluated. . Polylactic acid was decomposed, the molecular weight was greatly reduced, and it was difficult to cast. Furthermore, the polylactic acid discharged from the die was colored for decomposition and was not suitable for commercialization.

[Comparative Example 8]
In Comparative Example 8, as in Example 19, except that 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt was replaced with potassium acetate to produce a polylactic acid (A) composition, and the electrostatic casting property was evaluated. . The composition was difficult to cast due to degradation of polylactic acid and a significant decrease in molecular weight. Furthermore, the polylactic acid discharged from the die was colored for decomposition and was not suitable for commercialization.

[Comparative Example 9]
Further, in Comparative Example 8, as in Example 18, except that the amount of 3,5-dicarboxybenzenesulfonic acid tetraphenylphosphonium salt was changed by 3 wt%, and fluorination was carried out.
Yellowing of the polymer was observed, and the mirror surface cooling roll was markedly soiled. The soil was transferred to the film surface, and the product was judged to be rejected due to poor surface properties.

[Examples 20 to 21]
In the same manner as in Example 18, except that the sulfonic acid quaternary phosphonium salt was changed to the compounds shown in Table 4 and stereocomplexed to evaluate the electrostatic castability.
All the films had a maximum casting speed of 50 m / min, no pin-like defects were observed, the smoothness was good, and the electrostatic castability was acceptable. Furthermore, the physical properties of the stretched film were evaluated in the same manner as in Example 18. The results are summarized in Table 4.

The polylactic acid film of the present invention is a film having good flatness, no surface defects such as pin-like defects, and good thickness uniformity, a film for a capacitor, a film for a printer, a film for a ceramic liner, and a surface uniformity. It is suitable for optical applications because of its good properties.
According to the film manufacturing method of the present invention, a film having high speed, good flatness, and good surface properties can be stably cast.

Claims (11)

A polylactic acid film satisfying the following requirements.
(1) Surface property: 1 or less pin-like defects that can be visually observed in a sample having a width of 5 cm and a length of 50 cm.
(2) Thickness variation: The thickness variation value ΔRμm when the thickness of the sample is 50 cm (longitudinal direction) is measured with a continuous thickness meter (electronic micrometer) is within 7% of the average thickness Rμm.   The polylactic acid film according to claim 1, wherein the film formability improver is a sulfonic acid quaternary phosphonium salt. The sulfonic acid quaternary phosphonium salt is at least one selected from the group consisting of compounds represented by the formula (I) or (II) (hereinafter sometimes abbreviated as a specific phosphonium salt). The polylactic acid film according to any one of the above.

  Polylactic acid is extruded into a film form from a die, and an electrostatic charge is applied to one side of the film-like molten polylactic acid from an electrode provided near the contact point between the film-like molten polylactic acid and the cooling drum under the die. The manufacturing method of the polylactic acid film in any one of Claim 1 to 3 including the process of making it closely_contact | adhere to the surface and making it cool and solidify.   5. The method for producing a polylactic acid film according to claim 4, wherein a voltage is applied to the extent that electrostatic adhesion is caused between the film-like molten polylactic acid and an electrode provided in the vicinity of the contact point between the cooling drum.   The method for producing a polylactic acid film according to claim 4 or 5, wherein the electrode has a wire shape or a knife shape.   The method for producing a polylactic acid film according to any one of claims 4 to 6, wherein a high-temperature air stream is blown on the electrode and the vicinity thereof, and an exhaust nozzle is provided above the electrode to forcibly exhaust.   The method for producing a polylactic acid film according to any one of claims 4 to 7, wherein the polylactic acid is composed mainly of poly L-lactic acid or poly D-lactic acid.   Claimed to be uniaxially or biaxially stretched, and then heat-treated from the melting point (Tmh-50) to (Tmh-5) ° C. when the melting point of 190 ° C. or less is Tmh as measured by differential scanning calorimetry (DSC). Item 9. A method for producing a polylactic acid film according to Item 8.   Crystalline polylactic acid (B) containing a D-lactic acid unit as a main component and a copolymer unit other than D-lactic acid in an amount of 0 to 10 mol%, and a copolymer unit other than L-lactic acid as a main component Of polylactic acid (A) obtained by subjecting a crystalline polylactic acid (C) containing 0 to 10 mol% to a melt heat treatment at a weight ratio (B / C) = 10/90 to 90/10, The polylactic acid film according to any one of claims 1 to 3, wherein S) is 80% to 100%.   11. The heat treatment is performed at (Tmcs-50) to (Tmcs-5) ° C. when a melting point of 190 ° C. or higher measured by a differential scanning calorimeter (DSC) is defined as Tmsc. The manufacturing method of the polylactic acid film as described in any one of.