JP5123547B2 - Stereo complex polylactic acid film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polylactic acid film having high transparency and improved heat resistance and to provide a method for producing the same. <P>SOLUTION: The polylactic acid film is obtained by melt extrusion of a polylactic acid composition obtained by melting and kneading a poly-L-lactic acid and a poly-D-lactic acid and has a stereocomplex crystallization degree (S) measured by a differential scanning calorimeter (DSC measurement) represented by formula (1): S=ä&utri;Hmsc/(&utri;Hmsc+&utri;Hmh)}&times;100 of &ge;90% (wherein &utri;Hmh and &utri;Hmsc are each a melt enthalpy of a low-melting peak at a crystal melting peak temperature by DSC measurement of &lt;190&deg;C; and Hmsc is a melt enthalpy of a high-melting peak at a crystal melt peak temperature of &ge;190&deg;C) and a haze of &le;2%. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a stereocomplex polylactic acid film having high transparency and good heat resistance, and a method for producing the same. The present invention further relates to optical and packaging polylactic acid films.

Due to environmental problems such as global warming, concerns over oil depletion and supply conditions in oil-producing countries, oil prices have soared and the development of non-petroleum resins is required.
Among them, polylactic acid has not only the possibility of being a substitute for petroleum-based resin, but also has characteristics in optical properties such as transparency and low refractive index, and application development utilizing this is expected.

  However, polylactic acid usually has a low melting point of about 160 ° C. and has a problem in heat resistance such as melting and deformation. In addition, the biodegradability and degradation under a moist heat environment proceed at a relatively fast rate and there are problems in stability of physical properties.

  On the other hand, it is known that stereocomplex polylactic acid is formed by mixing poly-L-lactic acid composed of L-lactic acid units and poly-D-lactic acid composed of D-lactic acid units in a solution or in a molten state. Yes. (Patent Document 1 and Non-Patent Document 1) This stereocomplex polylactic acid has an extremely high melting point of 200 to 230 ° C. compared to poly L-lactic acid and poly D-lactic acid, and an interesting phenomenon showing high crystallinity has been discovered. Has been.

  This stereocomplex polylactic acid can be used in high-temperature processing and heat-resistant applications, and further improved in biodegradability and degradation under wet heat environments, and optical films and packaging films that take advantage of its transparency. Prolonged life expectancy is expected with highly transparent film.

  However, the stereocomplex polylactic acid is a composite composition of a poly L-lactic acid phase and a poly D-lactic acid phase (hereinafter sometimes referred to as a homo phase) and a stereo complex polylactic acid phase (hereinafter sometimes referred to as a complex phase). In DSC measurement, a low melting point crystal melting peak corresponding to a melting point of a normal phase crystal of 190 ° C. or lower and a high melting point crystal melting peak corresponding to a melting point of a complex phase crystal of 190 ° C. or higher are generally 2 The peak of the book is measured.

The polylactic acid film is formed by a method such as a melt extrusion method or a solution cast method, and the melt extrusion method is superior to the solution cast method in terms of productivity.
However, in the prior art, stereocomplex polylactic acid has (1) melt viscosity, (2) presence of crystal forms with different melting points as described above, (3) generation of bubbles by thermal decomposition, (4) crystal orientation, etc. The desired transparent film could not be obtained.

  In other words, when a stereocomplex polylactic acid having a high weight average molecular weight sufficient to form a film having practical strength and toughness is formed by melt extrusion, the melt viscosity is high. In addition to the unstretched film, streaky surface spots were generated not only in the unstretched film but also in the film after the stretching process, and it was difficult to obtain sufficient transparency by scattering the surface light.

  If the resin temperature is increased to reduce the melt viscosity, bubbles are generated due to the thermal decomposition of polylactic acid, which increases the possibility of haze deterioration due to an increase in internal haze, which is contrary to the purpose of obtaining a transparent film. May cause problems. In addition, when the molecular weight is reduced and the viscosity is lowered, the extruded film becomes brittle, and a problem that sufficient mechanical strength cannot be obtained is also encountered.

  In addition, when forming a melt-extruded film, it is necessary to dry the resin in advance in order to prevent hydrolysis.For example, when heat-drying in a hot air oven or the like, or when making a stereocomplex polylactic acid resin into a melt-extruded film, When passing through the melt preheating zone of the extruder, the stereocomplex polylactic acid crystallizes and a homophase crystal and a complex phase crystal grow.

  Both a low-melting-point homophase crystal and a high-melting-point complex phase crystal exist, and this mixture exists in two states with different flow characteristics even when melting and kneading are considered. As a result, a layer structure of a high melting point portion and a low melting point portion is generated, and flow spots are generated due to two-phase separation, causing light scattering, and it is difficult to obtain a uniform film with high transmittance.

  Furthermore, when the draw ratio of the polylactic acid film exceeds a specific range, transparency is deteriorated although it is a feature of stereocomplex polylactic acid. That is, in addition to the problem of low heat resistance when the draw ratio is low, the above-described crystallization proceeds at a relatively low temperature and the light transmittance deteriorates, and when the draw ratio is too high, the transparency deteriorates due to crystal orientation. was there.

JP 63-24014 A Macromolecules, 24, 5651 (1991).

The object of the present invention is a stereocomplex polylactic acid with excellent transparency that suppresses light scattering due to flow spots caused by high melt viscosity and homophase / complex phase separation, in addition to haze due to thermal decomposition of polylactic acid, and haze due to crystal orientation It is to propose a film and a method for producing the film.
As a further object of the present invention, a stereocomplex polylactic acid optical film and packaging film are proposed.

  As a result of earnest research to solve the above problems, surface roughening due to flow spots and phase separation spots generated in the extrusion process of stereocomplex polylactic acid is prevented, light scattering on the surface is improved, and polylactic acid is further improved. The present invention has been completed by completing a highly complex stereocomplex polylactic acid film by preventing the generation of bubbles due to thermal decomposition and suppressing internal haze.

That is, according to the present invention,
1. A polylactic acid (B) component containing 0 to 10 mol% of a component other than the L-lactic acid unit as a main component, and a component other than the D-lactic acid unit as a main component containing the D-lactic acid unit as 0 to 0 Adeka Stub (registered trademark) NA-71 was further added to polylactic acid (A) obtained by melt-kneading the polylactic acid (C) component containing 10 mol% with a weight ratio of (B / C) = 10/90 to 90/10. , Adekastab (registered trademark) NA-21, at least one phosphate ester metal salt selected from 0.01 to 5 parts by weight per 100 parts by weight of polylactic acid (A), and then melt-extruded, A polylactic acid film having a stereocomplex crystallinity (S) of 98% or more and a haze of 1% or less represented by the following formula measured with a differential scanning calorimeter (DSC measurement) can be provided.
[Equation 1]
S = {ΔHmsc / (ΔHmsc + ΔHmh)} × 100 (1)
(In the formula, ΔHmh represents the melting enthalpy of the low melting point melting peak temperature of less than 190 ° C. by DSC measurement, and ΔHmsc represents the melting enthalpy of the high melting point melting peak of 190 ° C. or more by DSC measurement. .)
The present invention also includes the following.
2. 2. The polylactic acid film as described in 1 above, wherein the crystal melting peak in DSC measurement is a single peak consisting essentially of a peak having a peak temperature of 190 ° C. or higher.
3. 3. The polylactic acid film according to 1 or 2 above, stretched in a uniaxial direction 2 to 7 times.
4). 3. The polylactic acid film according to 1 or 2 above, which is stretched 4 to 50 times in area magnification.
5. 5. The polylactic acid film according to any one of 1 to 4 above, wherein the carboxyl end group concentration is 0 to 10 eq / ton.
6). 6. The polylactic acid film according to any one of 1 to 5 above, wherein the polylactic acid (A) has a weight average molecular weight of 80,000 to 250,000.
7. A polylactic acid (B) component containing 0 to 10 mol% of a component other than the L-lactic acid unit as a main component, and a component other than the D-lactic acid unit as a main component containing the D-lactic acid unit as 0 to 0 The polylactic acid (C) component containing 10 mol% is melt-kneaded at a weight ratio of (B / C) = 10/90 to 90/10, and the polylactic acid (A) is further added to ADK STAB (registered trademark) NA. -71, Adekastab (registered trademark) NA-21, at least one phosphate metal salt selected from 0.01 to 5 parts by weight per 100 parts by weight of polylactic acid (A), and then the resin temperature 2. The method for producing a polylactic acid film according to 1 above, wherein melt extrusion is performed in a range of (Tmsc + 20) to (Tmsc + 50) (° C.).
(Here, Tmsc represents a peak temperature of a high melting point crystal melting peak having a peak temperature of 190 ° C. or higher in DSC measurement.)
8). 8. The production method according to 7 above, wherein after the melt extrusion, the film is uniaxially or biaxially stretched and then heat treated in a temperature range of (Tmh to Tmsc).
(Here, Tmsc represents a high melting point crystal melting peak temperature having a crystal melting peak temperature of 190 ° C. or higher by DSC measurement, and Tmh represents a low melting point crystal melting peak temperature having a crystal melting peak temperature of 190 ° C. or less by DSC measurement.)
9. 7. The optical polylactic acid film according to any one of 1 to 6 above.
10. The polylactic acid film for packaging according to any one of 1 to 6 above.

  The polylactic acid film of the present invention is a heat-resistant polylactic acid film having excellent transparency and improved light scattering due to high melt viscosity, flow spots caused by two-phase separation, and haze due to thermal decomposition. This polylactic acid film is suitable for optical and packaging applications. Further, 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 has an L-lactic acid unit as a main component, a polylactic acid (B) component containing 0 to 10 mol% of components other than the L-lactic acid unit, and a D-lactic acid unit as main components, and D-lactic acid. It is characterized by comprising a stereocomplex polylactic acid (A) having a haze of 1% or less obtained by melt-kneading a polylactic acid (C) component containing 0 to 10 mol% of components other than units.

The polylactic acid film of the present invention has a haze of 1% or less.
As the optical polylactic acid film, the higher the transparency, the more preferable, and the optical film preferably has a haze of 1% or less.

As the polylactic acid (B) component, polylactic acid substantially composed only of L-lactic acid units and copolymers with other monomers are shown, and in particular, it is composed substantially only of L-lactic acid units. Poly L-lactic acid is preferred.
In the polylactic acid (B) component, the L-lactic acid unit is 90 to 100 mol%, preferably 95 to 100 mol%, more preferably 98 to 100 mol%, from the viewpoint of physical properties such as crystallinity and film heat resistance.

That is, the copolymer component unit other than the D-lactic acid unit and / or the L-lactic acid unit is 0 to 10 mol%, preferably 0 to 5 mol%, more preferably 0 to 2 mol%.
This polylactic acid (B) component has crystallinity, and its melting point is preferably 150 ° C. or higher and 190 ° C. or lower, and more preferably 160 ° C. or higher and 190 ° C. or lower.

  If the melting point falls within these ranges, when stereocomplex polylactic acid is formed from the polylactic acid component, a stereocomplex crystal having a higher melting point can be formed and the crystallinity can be increased. .

  The polylactic acid (B) component used in the present invention preferably has a weight average molecular weight in the range of 80,000 to 250,000, and more preferably 100,000 to 250,000 or less. Particularly preferred is a range of 120,000 to 200,000.

  By using the polylactic acid (B) component in the weight average molecular weight range, stereocomplex polylactic acid can be produced industrially and efficiently, and while the flow spots of polylactic acid (A) are suppressed, the poly It is because it can match the transparency range of the lactic acid film.

  The polylactic acid (B) component used in the present invention may contain a copolymer component other than L-lactic acid, if desired, as long as the crystallinity is not impaired.

  Examples of the polylactic acid (C) component used in the present invention include polylactic acid substantially composed only of D-lactic acid units and copolymers with other monomers. It is preferable that it is poly D-lactic acid comprised only by.

  The polylactic acid (C) component has a D-lactic acid unit of 90 to 100 mol%, preferably 95 to 100 mol%, more preferably 98 to 100 mol% from the viewpoint of physical properties such as crystallinity and film heat resistance.

That is, the copolymer component unit other than L-lactic acid units and / or D-lactic acid is 0 to 10 mol%, preferably 0 to 5 mol%, more preferably 0 to 2 mol%.
This polylactic acid (C) component has crystallinity, and its melting point is preferably 150 ° C. or higher and 190 ° C. or lower, and more preferably 160 ° C. or higher and 190 ° C. or lower.

  If the melting point falls within these ranges, when stereocomplex polylactic acid is formed from the polylactic acid component, a stereocomplex crystal having a higher melting point can be formed and the crystallinity can be increased. .

  The polylactic acid (C) component used in the present invention preferably has a weight average molecular weight in the range of 80,000 to 250,000, more preferably 100,000 or more and 250,000 or less. Especially preferably, it is the range of 120,000 to 200,000.

  By using a polylactic acid (C) component having such a weight average molecular weight range, it becomes possible to produce a stereocomplex polylactic acid industrially and efficiently. It is because it can match the transparency range of the lactic acid film.

The polylactic acid (B) component and polylactic acid (C) component used in the present invention can contain a copolymer component other than L-lactic acid and D-lactic acid, as long as the crystallinity is not impaired. Examples of such copolymer components include, but are not limited to, hydroxycarboxylic acids such as glycolic acid, caprolactone, butyrolactone, propiolactone, ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, hexanediol, octanediol, decanediol, dodecanediol, aliphatic diols having 2 to 30 carbon atoms, succinic acid, maleic acid, adipic acid, 2 carbon atoms To 30 aliphatic dicarboxylic acids, terephthalic acid, isophthalic acid, hydroxybenzoic acid, hydride Aromatic diols such as quinone, may choose one or more monomers selected from an aromatic dicarboxylic acid.

  The method for producing the polylactic acid (B) component and the polylactic acid (C) component is not particularly limited, and a conventionally known method can be suitably used.

  For example, a method of directly dehydrating condensation of L- or D-lactic acid, a method of solid-phase polymerization of L- or D-lactic acid oligomers, L- or D-lactic acid once dehydrating and cyclizing to lactide, and then melt ring-opening polymerization Examples are methods.

  Among them, polylactic acid obtained by a direct dehydration condensation method or a melt ring-opening polymerization method of lactides is preferable from the viewpoint of quality and production efficiency, and among them, a melt ring-opening polymerization method of lactides is most preferably selected.

  Any catalyst can be used as the catalyst used in these production methods as long as the polylactic acid (B) component and (C) can be polymerized so as to have the above-mentioned predetermined characteristics.

  That is, lactide melt-opening polymerization catalysts include alkali metals, alkaline earth metals, rare earths, transition metals, fatty acid salts such as aluminum, germanium, tin, and antimony, carbonates, sulfates, phosphates, oxides, water Oxides, halides, alcoholates and the like are well known.

  Among these, a catalyst containing at least one selected from tin, aluminum, zinc, calcium, titanium, germanium, manganese, magnesium and rare earth elements is preferable. Hereinafter, the catalyst may be abbreviated as a specific metal-containing catalyst. Such specific metal-containing catalysts are conventionally known and exemplified as follows.

  Stannous chloride, stannous bromide, stannous iodide, stannous sulfate, stannic oxide, tin myristate, tin octylate, tin stearate, tetraphenyltin, tin methoxide, tin ethoxide, tin Butoxide, aluminum oxide, aluminum acetylacetonate, aluminum isopropoxide, aluminum-imine complex titanium tetrachloride, ethyl titanate, butyl titanate, glycol titanate, titanium tetrabutoxide, zinc chloride, zinc oxide, diethyl zinc, trioxide Examples include antimony, antimony tribromide, antimony acetate, calcium oxide, germanium oxide, manganese oxide, manganese carbonate, manganese acetate, magnesium oxide, and yttrium alkoxide.

  Considering the catalytic activity and few side reactions, stannous chloride, stannous bromide, stannous iodide, stannous sulfate, stannic oxide, stannous myristate, stannous octoate, stannous stearate Preferred examples include tin-containing compounds such as tetraphenyltin, and aluminum-containing compounds such as aluminum acetylacetonate, aluminum butoxide, and aluminum-imine complexes. More preferably, the following are illustrated.

  Specifically, diethoxytin, dinonyloxytin, tin myristate, tin octylate, tin stearate, tin chloride, aluminum acetylacetonate, aluminum isopropoxide and the like are further exemplified.

The amount of the catalyst used is 0.42 × 10 ⁻⁴ to 100 × 10 ⁻⁴ (mol) per kg of lactide, and 1.68 × 10 ^{−4 in} consideration of reactivity, color tone and stability of the obtained polylactide. To 42.1 × 10 ⁻⁴ (mol), particularly preferably 2.53 × 10 ⁻⁴ to 16.8 × 10 ⁻⁴ (mol).

  The polylactic acid (B) component and the polylactic acid (C) component are prepared by removing the polymerization catalyst by a conventionally known method, for example, by washing with a solvent, or deactivating and deactivating the catalytic activity. And preferred because of the melt stability and wet heat stability of the polylactic acid film.

  Examples of the deactivator used for catalyst deactivation of the polylactic acid melt-opened and polymerized in the presence of the metal-containing catalyst include the following compounds.

  That is, from an organic ligand consisting of a group of chelate ligands having an imino group and capable of coordinating to a specific metal-based polymerization catalyst, a phosphorus oxoacid, a phosphorus oxoacid ester, and an organic phosphorus oxoacid compound group represented by the formula (2) It is a resin containing at least one selected and added in an amount of 0.3 to 20 equivalents per equivalent of a metal element of the specific metal-containing catalyst.

_{X 1 -P (= O) m} (OH) n (OX 2) 2-n (2)
(In the formula, m is 0 or 1, n is 1 or 2, and X ₁ and X ₂ each independently represents a hydrocarbon group optionally having a substituent having 1 to 20 carbon atoms.)
The amount of the quenching agent 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.

  The imine compound used in the present invention is a phenol tetradentate chelate ligand having an imino group in its structure and capable of coordinating with a metal polymerization catalyst. Since the imine compound of the present invention is not a Bronsted acid or a base like conventional catalyst deactivators, it is possible to improve the thermal stability without deteriorating the hydrolysis resistance of the polylactic acid resin composition. is there. Examples of such imine compounds include N, N′-bis (salicylidene) ethylenediamine, N, N′-bis (salicylidene) propanediamine, and the like.

Examples of the phosphorus oxoacid include dihydridooxoline (I) acid, dihydridotetraoxodiphosphorus (II, II) acid, hydridotrioxoline (III) acid, dihydridopentaoxodiphosphoric acid (III), and hydridopentaoxodioxide. (II, IV) acid, dodecaoxohexaphosphorus (III) acid, hydridooctaoxotriphosphoric acid (III, IV, IV) acid, octaoxotriphosphoric acid (IV, III, IV) acid, hydridohexaoxodiphosphorus (III, V) ) Low oxidation number phosphorus having an acid number of 5 or less, such as acid, hexaoxodiphosphorus (IV) acid, decaoxotetralin (IV) acid, hendecaoxotetralin (IV) acid, eneoxooxo triphosphoric acid (V, IV, IV) acid acid, the formula represented by _{(xH 2 O · yP 2 O} 5), x / y = 3 of orthophosphoric acid, 2> a x / y> 1, diphosphate from the degree of condensation Polyphosphoric acid called triphosphoric acid, tetraphosphoric acid, pentaphosphoric acid and the like, and mixtures thereof, metaphosphoric acid represented by x / y = 1, especially trimetaphosphoric acid, tetrametaphosphoric acid, 1> x / y> Ultraphosphoric acid represented by 0 and having a network structure with a part of the phosphorus pentoxide structure, and monovalent and polyhydric alcohols of these acids, partial esters of polyalkylene glycols, and complete ester Illustrated. From the catalyst deactivation ability, acids or acidic esters are preferably used.

  There are no particular restrictions on the alcohol that forms the ester of the phosphorus oxoacid, but the monohydric alcohol is preferably an alcohol represented by the formula (3) which may have a substituent having 1 to 22 carbon atoms. used.

Y-OH (3)
(In the formula, Y represents a hydrocarbon group which may have a substituent having 1 to 22 carbon atoms.)
Specific examples include methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, 2-ethylhexyl alcohol, decanol, dodecanol, benzyl alcohol, cyclohexyl alcohol, hexyl alcohol, phenol, hexadecyl alcohol and the like.

  Examples of the polyhydric alcohol include polyhydric alcohols and sugar alcohols represented by the formula (4) which may have a substituent having 2 to 22 carbon atoms.

X (—OH) _a (4)
(In the formula, X represents a hydrocarbon group which may have a substituent having 2 to 22 carbon atoms, and a represents an integer of 2 to 6.)
Specifically, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, glycerin, pentaerythritol, trimethylolpropane, polyethylene glycol, polypropylene glycol, myo-inositol, D -, L-inositol, neositol such as scyllo-inositol, cyclitol and the like.

  Particularly preferably, phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, trimetaphosphoric acid, tetrametaphosphoric acid, phenylphosphonic acid, benzylphosphinic acid, dibutyl phosphate, dinonyl phosphate, N′-bis (salicylidene) ethylenediamine , N, N′-bis (salicylidene) propanediamine, and phosphoric acid, phosphorous acid, and pyrophosphoric acid are particularly preferable.

  These deactivators may be used alone or in combination depending on the case. These deactivators are 0.3 to 20 equivalents, more preferably 0.5 to 15 equivalents, more preferably 0.5 to 10 equivalents, particularly preferably 0, per equivalent of the metal element of the specific metal-containing catalyst. .6 to 7 equivalents are used.

  If the amount of the deactivator used is too small, the activity of the catalyst metal cannot be lowered sufficiently, and if used excessively, the deactivator may cause decomposition of the resin, which is not preferable.

  The polylactic acid (A) of the present invention is obtained by melt-kneading the above-mentioned polylactic acid (B) component and polylactic acid (C) component at 220 to 300 ° C. in a weight ratio range of 10/90 to 90/10. Can be obtained.

  The weight mixing ratio of the polylactic acid (B) component and the polylactic acid (C) component is preferably 30/70 to 70/30, more preferably 40 / to increase the stereocomplex crystallinity of the polylactic acid (A). A range of 60-60 / 40 is selected. A mixing ratio as close to 50/50 as possible is preferably selected.

  The melt kneading temperature is selected in the range of 230 to 300 ° C., preferably 240 to 280 ° C., more preferably 245 to 275 ° C., from the viewpoint of improving the stability of polylactic acid and the degree of stereocomplex crystallinity.

  By melt-kneading in such a mixing ratio and kneading temperature range, the stereocomplex crystallinity (S) of polylactic acid (A) can be increased to 80% or more, which is preferable. The stereocomplex crystallinity (S) of the polylactic acid film of the present invention is 98% or more, particularly preferably 100%.

  The melt kneading method is not particularly limited, but a conventionally known batch type or continuous type melt mixing apparatus is preferably used. For example, melt stirring tank, single-screw or twin-screw extruder, kneader, non-shaft vertical stirring tank, Sumitomo Heavy Industries Viola rack, Mitsubishi Heavy Industries N-SCR, Hitachi glass blade, lattice blade or Kenix stirrer, or Sulzer SMLX type static mixer equipped pipe type polymerization equipment can be used, but it is a self-cleaning type polymerization equipment in terms of productivity, quality of polylactic acid, especially color tone, non-axial vertical stirring tank, N-SCR, biaxial An extrusion ruder or the like is preferably used.

The stereocomplex crystallinity (S) of the polylactic acid (A) of the present invention is 80% or more, preferably 90% or more, more preferably 95% or more.
Particularly preferably, the stereocomplex crystallinity (S), which is a single peak of a high melting point peak due to stereocomplex polylactic acid in DSC measurement, is 100%.

  Melting and kneading polylactic acid (B) component and polylactic acid (C) component in such a mixing ratio range, mixing polylactic acid (A) having such a stereocomplex crystallinity (S) range with a phosphoric acid ester metal salt described later Later, forming a melt-extruded film is suitable for producing a polylactic acid film that can suppress the flow spots due to the above-described two-phase separation, has good transparency, and has excellent heat resistance.

The weight average molecular weight of the polylactic acid (A) and the polylactic acid film of the present invention is preferably in the range of 80,000 to 250,000, and more preferably 100,000 to 250,000. Particularly preferred is a range of 120,000 to 200,000.
Such a weight average molecular weight range is suitable for suppressing flow spots and improving transparency, and for enhancing the mechanical properties and durability of the film.

  In the present invention, the melting enthalpy of the complex phase crystal of the polylactic acid film is 35 J / g or more, preferably 40 J / g to 80 J / g. The crystal melting enthalpy of 100% polylactic acid crystals is said to be 93 J / g, and it can be said that the polylactic acid film having the above crystallization enthalpy value has a sufficiently high crystallinity and high heat resistance.

  The polylactic acid film of the present invention contains at least one phosphate metal salt selected from ADK STAB (registered trademark) NA-71 and ADK STAB (registered trademark) NA-21. By blending such an agent, the stereocomplex crystallinity of a polylactic acid film or the like can be made 98% or more.

In particular, this is effective for setting the stereocomplex crystallinity, which is a single peak of a high melting point peak due to stereocomplex polylactic acid in DSC measurement, to 100%.
Such polylactic acid (A) having a high stereocomplex crystallinity is suitable for realizing a high stereocomplex crystallinity, transparency, and heat resistant film.

Various agents are known as nucleating agents for improving the crystallinity of polylactic acid. In the present invention, “ADEKA STAB (registered trademark)” NA-71 manufactured by ADEKA Co., Ltd. used as a phosphate metal salt, ADEKA Co., Ltd. “Adekastab (registered trademark)” NA-21 manufactured by the Company is suitable for improving the stereocomplex crystallinity and improving the transparency of the polylactic acid film, although the clear mechanism of action is unknown.
Among them, “Adekastab (registered trademark)” NA-71 and “Adekastab (registered trademark)” NA-21 in the form of fine particles having a high dispersibility and an average particle size of 5 μm or less that have been pulverized and classified are preferable.

The amount of the phosphate metal salt used is in the range of 0.01 to 5 parts by weight per 100 parts by weight of the polylactic acid (A). If the amount is less than 0.01 parts by weight, the desired effect is hardly observed or is too small for practical use.
On the other hand, if it is used in an amount of more than 5 parts by weight, it is not preferable because thermal decomposition or deterioration coloring may occur during film formation.

Accordingly, the range of 0.05 to 4 parts by weight is preferably selected, and the range of 0.1 to 3 parts by weight is particularly preferably selected.
By using the phosphoric acid ester metal salt in such a quantitative ratio, it is possible to suppress the formation of flow spots caused by two-phase separation during film formation of the present invention, and to produce a film with good transparency and good heat resistance.

  In addition, the phosphoric acid ester metal salt used in the present invention is preferably one having a particle size as small as possible, particularly one having a small content ratio of large particles exceeding 10 μm from the viewpoint of the transparency of the polylactic acid film. To 10 μm are preferably used. More preferably, 0.05 to 7 μm is selected. When the content ratio of large particles exceeding 10 μm exceeds 20%, the haze of the polylactic acid film is increased, which is not preferable.

  For the phosphoric acid ester metal salt having such a particle size, a commercially available “ADK STAB (registered trademark)” NA-71 and “ADEKA STAB (registered trademark)” NA-21 manufactured by ADEKA Co., Ltd. are required by a ball mill, a sand mill, a hammark crusher, and an atomizer. Depending on the condition, it can be obtained by pulverizing and classifying with various classifiers.

  It is industrially difficult to make the particle size of the phosphoric acid ester metal salt smaller than 0.01 μm, and it is not necessary to make it practically so small. However, if the content ratio of particles having a particle size larger or larger than 10 μm is high, the problem that the film haze increases is undesirably increased.

In the film of the present invention, the amount of carboxyl groups is preferably 10 equivalents / 10 ⁶ g or less from the viewpoints of stability during film casting, hydrolysis resistance suppression, and weight average molecular weight reduction suppression, and 5 equivalents / 10 ⁶ g or less. More preferably, it is more preferably 2 equivalents / 10 ⁶ g or less.

  In the polylactic acid of the present invention, the carboxyl group end group can be reduced depending on the application by adding a carboxyl group and a reactive carboxyl group-sealing agent. Preferred for stability.

Carboxy group capping agent adds terminal carboxyl group of polylactic acid resin to capping and seals carboxyl group of low molecular weight compounds such as lactic acid, lactic acid, formic acid, etc. produced by decomposition reaction of polylactic acid resin and various additives The resin can be stabilized, and there is also an advantage that the resin temperature at the time of film formation can be raised to a temperature that can suppress flow spots.
As such a carboxyl group-capping agent, it is preferable to use at least one compound selected from a carbodiimide compound, an epoxy compound, an oxazoline compound, an oxazine compound, and an isocyanate compound, and among them, a carbodiimide compound is preferable.

  Examples of the carbodiimide compound used in the present invention include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dioctylcarbodiimide, octyldecylcarbodiimide, di-t-butylcarbodiimide, dibenzylcarbodiimide, diphenylcarbodiimide, N-octadecyl-N′-phenylcarbodiimide. N-benzyl-N′-phenylcarbodiimide, N-benzyl-N′-tolylcarbodiimide, di-o-toluylcarbodiimide, di-p-toluylcarbodiimide, bis (p-nitrophenyl) carbodiimide, bis (p-aminophenyl) Carbodiimide, bis (p-hydroxyphenyl) carbodiimide, bis (p-chlorophenyl) carbodiimide, bis (o-chlorophenol) Nyl) carbodiimide, bis (o-ethylphenyl) carbodiimide, bis (p-ethylphenyl) carbodiimide bis (o-isopropylphenyl) carbodiimide, bis (p-isopropylphenyl) carbodiimide, bis (o-isobutylphenyl) carbodiimide, bis ( p-isobutylphenyl) carbodiimide, bis (2,5-dichlorophenyl) carbodiimide, p-phenylenebis (o-toluylcarbodiimide), p-phenylenebis (cyclohexylcarbodiimide), p-phenylenenebis (p-chlorophenylcarbodiimide), 2, 6,2 ′, 6′-tetraisopropyldiphenylcarbodiimide, hexamethylenebis (cyclohexylcarbodiimide), ethylenebis (phenylcarbodiimide), ethylenebiethylene (Cyclohexylcarbodiimide), bis (2,6-dimethylphenyl) carbodiimide, bis (2,6-diethylphenyl) carbodiimide, bis (2-ethyl-6-isopropylphenyl) carbodiimide, bis (2-butyl-6-isopropylphenyl) ) Carbodiimide, bis (2,6-diisopropylphenyl) carbodiimide, bis (2,6-di-t-butylphenyl) carbodiimide, bis (2,4,6-trimethylphenyl) carbodiimide, bis (2,4,6- Triisopropylphenyl) carbodiimide, bis (2,4,6-tributylphenyl) carbodiimide, diβ-naphthylcarbosiimide, N-tolyl-N′-cyclohexylcarbosiimide, N-tolyl-N′-phenylcarbosiimide, etc. Mono or poly Diimide compounds.

Of these, bis (2,6-diisopropylphenyl) carbodiimide and 2,6,2 ′, 6′-tetraisopropyldiphenylcarbodiimide are preferred from the viewpoints of reactivity and stability.
Of these, industrially available dicyclohexylcarbodiimide and diisopropylcarbodiimide are also suitable.

Furthermore, a commercially available polycarbodiimide compound as the polycarbodiimide compound can be suitably used without the need for synthesis.
As such a commercially available polycarbodiimide compound, for example, “Carbodilite (registered trademark)” LA-1, which is commercially available from Nisshinbo Chemical Co., Ltd. and sold under the trade name of “Carbodilite (registered trademark)”, HMV-8CA, Line Chemie Illustrate "STABAKZOL (registered trademark)" I, "STABAKZOL (registered trademark)" P, "STABAXOL (registered trademark)" P100, etc., which are commercially available under the trade name "STABAXOL (registered trademark)" from Japan Co., Ltd. Can do.

  As an epoxy compound, a glycidyl ether compound, a glycidyl ester compound, a glycidyl amine compound, a glycidyl imide compound, a glycidyl amide compound, and an alicyclic epoxy compound can be preferably used. By blending such an agent, a polylactic acid resin composition and a molded product having excellent mechanical properties, moldability, heat resistance, and durability can be obtained.

  Examples of glycidyl ether compounds include stearyl glycidyl ether, phenyl glycidyl ether, o-phenylphenyl glycidyl ether, ethylene oxide lauryl alcohol glycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, poly Tetramethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, and other bisphenol A diphenols obtained by condensation reaction of bis (4-hydroxyphenyl) methane with epichlorohydrin Glycidyl ether type epoxy resin, etc. It can be mentioned. Of these, bisphenol A diglycidyl ether type epoxy resins are preferred.

  Examples of glycidyl ester compounds include, for example, benzoic acid glycidyl ester, cyclohexanecarboxylic acid glycidyl ester, stearic acid glycidyl ester, linoleic acid glycidyl ester, linolenic acid glycidyl ester, terephthalic acid diglycidyl ester, phthalic acid diglycidyl ester, cyclohexanedicarboxylic acid diacid Examples include glycidyl ester, adipic acid diglycidyl ester, succinic acid diglycidyl ester, dodecanedioic acid diglycidyl ester, trimellitic acid triglycidyl ester, and pyromellitic acid tetraglycidyl ester. Of these, glycidyl benzoate and glycidyl versatate are preferred.

  Examples of the glycidylamine compound include tetraglycidylamine diphenylmethane, triglycidyl-p-aminophenol, diglycidylaniline, diglycidyltoluidine, tetraglycidylmetaxylenediamine, triglycidyl isocyanurate, and the like.

  Examples of glycidylimide and glycidylamide compounds include, for example, N-glycidylphthalimide, N-glycidyl-4-methylphthalimide, N-glycidyl-3-methylphthalimide, N-glycidyl-4,5-dimethylphthalimide, N-glycidyl- 3,6-dimethylphthalimide, N-glycidyl-3,4,5,6-tetrabromophthalimide, N-glycidyl-4-n-butyl-5-bromophthalimide, N-glycidylsuccinimide, N-glycidyl-1, 2,3,4-tetrahydrophthalimide, N-glycidylmaleimide, N-glycidyl-α-ethylsuccinimide, N-glycidylbenzamide, N-glycidyl-p-methylbenzamide, N-glycidylnaphthamide, N-glycidylstearylamide etc It is below. Of these, N-glycidylphthalimide is preferable.

  Examples of alicyclic epoxy compounds include 3,4-epoxycyclohexyl-3,4-cyclohexylcarboxylate, bis (3,4-epoxycyclohexylmethyl) adipate, vinylcyclohexene diepoxide, N-methyl- 4,5-epoxycyclohexane-1,2-dicarboxylic acid imide, N-phenyl-4,5-epoxycyclohexane-1,2-dicarboxylic acid imide, and the like.

  As other epoxy compounds, epoxy-modified fatty acid glycerides such as epoxidized soybean oil, epoxidized linseed oil, and epoxidized whale oil, phenol novolac type epoxy resins, cresol novolac type epoxy resins, and the like can be used.

  Examples of oxazoline compounds used in the present invention include 2-butoxy-2-oxazoline, 2-decyloxy-2-oxazoline, 2-stearyloxy-2-oxazoline, 2-cyclohexyloxy-2-oxazoline, 2-allyloxy-2 -Oxazoline, 2-cresyloxy-2-oxazoline, 2-o-propylphenoxy-2-oxazoline, 2-p-phenylphenoxy-2-oxazoline, 2-methyl-2-oxazoline, 2-heptyl-2-oxazoline, 2 -Oleyl-2-oxazoline, 2-cyclohexyl-2-oxazoline, 2-methallyl-2-oxazoline, 2-phenyl-2-oxazoline, 2-benzyl-2-oxazoline, 2-o-propylphenyl-2-oxazoline, 2 -M-propylphenyl-2 Oxazoline, 2-p-phenylphenyl-2-oxazoline, 2-p-propylphenyl-2-oxazoline, 2,2′-bis (2-oxazoline), 2,2′-bis (4-methyl-2-oxazoline) ), 2,2′-bis (4-butyl-2-oxazoline), 2,2′-m-phenylenebis (2-oxazoline), 2,2′-p-phenylenebis (4-methyl-2-oxazoline) ), 2,2′-ethylenebis (2-oxazoline), 2,2′-tetramethylenebis (2-oxazoline), 2,2′-hexamethylenebis (2-oxazoline), 2,2′-octamethylene Bis (2-oxazoline), 2,2′-ethylenebis (4-methyl-2-oxazoline), 2,2′-tetramethylenebis (4,4′-dimethyl-2-oxazoline) 2,2'-cyclohexylene-bis (2-oxazoline), 2,2'-diphenylenebis (4-methyl-2-oxazoline) and the like. Furthermore, the polyoxazoline compound etc. which contain the said compound as a monomer unit are mentioned.

  Examples of oxazine compounds used in the present invention include 2-methoxy-5,6-dihydro-4H-1,3-oxazine, 2-propyloxy-5,6-dihydro-4H-1,3-oxazine, 2- Butoxy-5,6-dihydro-4H-1,3-oxazine, 2-hexyloxy-5,6-dihydro-4H-1,3-oxazine, 2-heptyloxy-5,6-dihydro-4H-1, 3-oxazine, 2-nonyloxy-5,6-dihydro-4H-1,3-oxazine, 2-decyloxy-5,6-dihydro-4H-1,3-oxazine, 2-cyclopentyloxy-5,6-dihydro -4H-1,3-oxazine, 2-allyloxy-5,6-dihydro-4H-1,3-oxazine, 2-crotyloxy-5,6-dihydro-4H-1,3-oxa Such as emissions, and the like.

Further, 2,2′-bis (5,6-dihydro-4H-1,3-oxazine), 2,2′-ethylenebis (5,6-dihydro-4H-1,3-oxazine), 2,2 ′ -Propylene bis (5,6-dihydro-4H-1,3-oxazine), 2,2'-hexamethylene bis (5,6-dihydro-4H-1,3-oxazine), 2,2'-p- Phenylenebis (5,6-dihydro-4H-1,3-oxazine), 2,2′-m-phenylenebis (5,6-dihydro-4H-1,3-oxazine), 2,2′-P, P′-diphenylenebis (5,6-dihydro-4H-1,3-oxazine), and the like. Furthermore, the polyoxazine compound etc. which contain the above-mentioned compound as a monomer unit are mentioned.
Among the oxazoline compounds and oxazine compounds, 2,2′-m-phenylenebis (2-oxazoline) and 2,2′-p-phenylenebis (2-oxazoline) are preferably selected.

Examples of the isocyanate compound used in the present invention include aromatic, aliphatic, and alicyclic isocyanate compounds and mixtures thereof.
Examples of the monoisocyanate compound include phenyl isocyanate, tolyl isocyanate, dimethylphenyl isocyanate, cyclohexyl isocyanate, butyl isocyanate, and naphthyl isocyanate.

  Specific examples of the diisocyanate include 1,5-naphthalene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2 , 4-tolylene diisocyanate, 2,6-tolylene diisocyanate, (2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate) mixture, hexamethylene diisocyanate, cyclohexane-4,4′-diisocyanate, xylylene diisocyanate , Isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, methylcyclohexane diisocyanate, tetramethylxylylene diisocyanate, 2, - it can be exemplified diisopropylphenyl-1,4-diisocyanate, and the like.

Among these isocyanate compounds, aromatic isocyanates such as 4,4′-diphenylmethane diisocyanate and phenyl isocyanate are preferable.
The said carboxy group sealing agent can select and use 1 type or 2 or more types of compounds suitably.

  The amount of the carboxyl group sealing agent used is preferably 0.01 to 10 parts by weight, more preferably 0.03 to 5 parts by weight per 100 parts by weight of the polylactic acid resin (A). In the present invention, a sealing reaction catalyst may be further used.

  Examples of such compounds include alkali metal compounds, alkaline earth metal compounds, tertiary amines, imidazole compounds, quaternary ammonium salts, phosphine compounds, phosphonium compounds, phosphate esters, organic acids, Lewis acids, and the like. .

  In order to make the polylactic acid (A) of the present invention contain the above-mentioned nucleating agent and / or carboxy group blocking agent, the polylactic acid (B) component, the method of previously containing the polylactic acid (C) component, polylactic acid (B ) Component and polylactic acid (C) component can be blended and contained at the time of melt-kneading, or melt-kneading the polylactic acid (B) component and polylactic acid (C) component to form a casting film.

The polylactic acid (A) composition can be solidified and pelletized once, but it can also be melt extruded without solidification to form a film.
For blending these agents, 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.

Furthermore, in the film of the present invention, a lubricant can be applied in the polylactic acid for the purpose of improving film winding and running performance, as long as the object of the present invention is not violated.
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 mix | blended in 0.01-0.5 wt% of range with respect to polylactic acid.
In addition to these agents, an antioxidant, an antistatic agent, a colorant, a pigment, a fluorescent brightening agent, a plasticizer, a crosslinking agent, an ultraviolet absorber, and other resins are required as long as they do not contradict the spirit of the present invention. It can be added depending on.
These agents can be appropriately blended at the stage between the start of polylactic acid polymerization and before film formation.

As an addition method, an agent-containing polylactic acid can be produced by using a generally known agent charging method.
Moreover, conventionally well-known various methods can be used suitably for adding an agent to polylactic acid. 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.
The polylactic acid containing the phosphoric acid ester metal salt and the carboxyl group sealing agent thus obtained can be once pelletized as it is and then supplied to the film forming apparatus.

  The unstretched film of the present invention comprises a polylactic acid composition containing a phosphoric acid ester metal salt, optionally a carboxyl group blocking agent, a sulfonic acid quaternary phosphonium salt, a lubricant and the like at a temperature of (Tmsc + 20) ° C. to (Tmsc + 50) ° C. It is manufactured by extruding a molten film at a temperature onto a cooling drum and then bringing the film into close contact with a rotating cooling drum and cooling.

  The resin temperature is a temperature at which the resin has sufficient fluidity, that is, a range of (Tmsc + 20) ° C. to (Tmsc + 50) (° C.), but melt extrusion is preferably performed at a temperature at which the resin does not decompose. Preferably, a temperature of 240 ° C. to 300 ° C., more preferably 245 ° C. to 280 ° C., particularly preferably 250 ° C. to 275 ° C. is employed, in which flow spots are not easily generated.

During film casting, it is preferable to produce an unstretched film by cooling and solidifying with a cooling drum while applying an electrostatic charge from an electrode by an electrostatic contact method. At this time, the electrode to which the electrostatic charge is applied is a wire or a knife The shape of a shape is used suitably.
The surface material of the electrode is preferably platinum. That is, when film formation is continued for a long time, there is a concern that impurities sublimated from the film may adhere to the electrode surface or the electrode surface may be deteriorated, so that the ability to apply static electricity is reduced. 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 (A) supplied to the extruder is preferably dried before supplying the extruder in order to suppress decomposition during melting. The water content is particularly preferably 100 ppm or less.

  The unstretched film is 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 temperature is such that the unstretched film can be stretched, that is, the glass transition temperature of polylactic acid (hereinafter sometimes referred to as Tg) to (Tg + 80) ° C. or less. Heat and stretch at least uniaxially.

  The draw ratio is selected in the range of 2 to 7 times for a uniaxially stretched film, and 4 to 50 times for the area ratio of a biaxially stretched film.

In biaxial stretching, in addition to simply setting the area ratio within the above range, reducing the difference between the longitudinal and lateral stretching ratios to balance balances the longitudinal and lateral values such as shrinkage and elastic modulus. Is necessary. If the draw ratio does not satisfy the above range, the transparency of the polylactic acid film is lowered, which is not preferable.
The biaxially stretched film is produced by, for example, a longitudinal-transverse 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. can do.

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.
The uniaxially stretched film or the biaxially stretched film is preferably heat treated.

Further heat treatment at a temperature not higher than the high temperature phase melting point Tmsc of the polylactic acid (A) and cooling to room temperature can provide a uniaxially stretched heat treated film or a biaxially stretched heat treated film.
Preferably, the heat treatment temperature is a temperature range from the low-temperature phase melting point Tmh to the high-temperature phase melting point Tmsc (° C.), so that the film is hardly broken and has a sufficient heat setting effect, and has good dimensional stability. It can be a film.
The uniaxially stretched film or the biaxially stretched film thus obtained can be subjected to, for example, a surface activation treatment such as plasma treatment, amine treatment, or corona treatment by a conventionally known method.

Since the polylactic acid film of the present invention has good transparency and good heat resistance, it is 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 thickness of about 5 μm). Film), heat sensitive stencil printing film, magnetic recording film (for example, for QIC tape: 1/4 inch tape for computer recording), and non-glare film (for example, film having a thickness of 50 μm or less).
In particular, a film having a haze of 1% or less is useful for optical applications.

As an optical film, it can be used for a protective film for a polarizing plate, an antireflection film, an antiglare film and the like. A polylactic acid film has a characteristic that the optical elastic modulus is low. For example, since a change in optical characteristics due to a stress applied to an edge of a large area liquid crystal screen is small, a uniform screen can be obtained. Furthermore, when a polylactic acid film is used as a protective film for the polarizing plate, the optical properties can be stably obtained by keeping the birefringence low.
Furthermore, since the refractive index of the polylactic acid film of the present invention tends not to change depending on the draw ratio, it is difficult for retardation spots due to stretch spots to occur.

Further, due to water vapor permeability, polyvinyl alcohol (PVA), which is an aqueous casting film, can be sufficiently dried, and can be used as an alternative to triacetyl cellulose (TAC).
In addition, when used as a packaging film for foods, the contents are not only visible, but also have high heat resistance, so there are merits such as heat sterilization and heating in a microwave oven. is there.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention does not receive any limitation by this. In addition, each value in an Example was calculated | required according to the following method.
(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 has the following configuration, 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). And measured.
Detector: differential refractometer RID-6A manufactured by Shimadzu Corporation
Pump: Shimadzu Corporation LC-9A
Column: TSKgel G3000HXL, TSKgelG4000HXL, TSKgelG5000HXL and TSKguardcolumnHXL-L manufactured by Tosoh Corporation (2) Crystal melting point, heat of crystal melting (ΔHmh, ΔHmsc) and stereocomplex crystallinity (S):
It measured with DSC7 differential scanning calorimeter (DSC) by Perkin Elmer Co., Ltd. A 10 mg sample was heated from 30 ° C. to 250 ° C. at a temperature increase rate of 20 ° C./min in a 1st RUN under a nitrogen atmosphere, and crystal melting temperatures (Tmh), (Tmsc), and crystal melting heat (ΔHmh) ( ΔHmsc) was measured. The stereocomplex crystallinity (S) is a polylactic acid composed of a poly L-lactic acid component and a poly D-lactic acid component. From (ΔHmsc), the following formula was obtained.
[Equation 2]
S (%) = ΔHmsc / (ΔHmh + ΔHmsc) × 100 (1)
(3) 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 the polylactic acid resin (A) was formed into a film, if the melt stability was 80% or more, normal melt pressing could be performed without any problem, and it was determined that the melt stability passed.
The reduced viscosity (η _sp / c) was measured by dissolving 1.2 mg of a sample in 100 ml of [tetrachloroethane / phenol = (6/4) wt mixed solvent] and using an Ubbelohde viscosity tube at 35 ° C.
(4) Wet heat stability (%):
The sample was held at 80 ° C. and 90% RH for 11 hr, and the retention rate (%) of the reduced viscosity (η _sp / c) was measured and used as a wet heat stability and durability parameter. When the parameter was 80% or more, the polylactic acid resin assembled film could be stably used under normal wet heat conditions, and the durability was determined to be acceptable. If it was 90% or more, it was judged to be particularly good.
(5) Haze measurement:
The measurement was performed according to 6.4 of JIS K7105-1981 using Nippon Denshoku Co., Ltd. Hazemeter MDH2000, using a 50 μm film. (6) Optical purity Optical purity is measured by using an optical rotation measurement device to measure the optical rotation using a dilute solution of polylactic acid dissolved in chloroform. In the case of 100% poly L lactic acid having an optical purity of 100%, and in the case of 100% poly D lactic acid having an optical purity of -100%, the optical purity was determined as a percentage determined from the optical rotation of the sample by a proportional formula.

[Reference Example 1] Example of synthesis of polylactic acid by melt ring-opening polymerization of lactide:
A vertical stirring tank (40 L) equipped with a full-zone blade equipped with a vacuum pipe, a nitrogen gas pipe, a catalyst, an L-lactide solution addition pipe, and an alcohol initiator addition pipe was purged with nitrogen, and L-lactide 30 kg, stearyl alcohol 0.90 kg ( 0.030 mol / kg), tin octylate 6.14 g (5.05 × 10 ⁻⁴ mol / 1 kg) was charged, and the temperature was raised to 150 ° C. in an atmosphere of nitrogen pressure 106.4 kPa, and the contents were dissolved. At that time, stirring was started and the internal temperature was further raised to 190 ° C. Since the reaction started when the internal temperature exceeded 180 ° C., cooling was started, and the internal temperature was maintained from 185 ° C. to 190 ° C., and the reaction was continued for 1 hour.
Further, with stirring, the reaction was carried out for 1 hour at a nitrogen pressure of 106.4 kPa and an internal temperature of 200 ° C. to 210 ° C. Then, stirring was stopped and a phosphorus-based catalyst deactivator was added.
After removing the bubbles by standing still for 20 minutes, the internal pressure was increased from 2 to 3 atm with nitrogen pressure, the prepolymer was extruded into a chip cutter, and the prepolymer having a weight average molecular weight of 130,000 and a molecular weight dispersion of 1.8 was pelleted. Turned into.
Further, the pellets are dissolved by an extruder, charged into a non-axial vertical reactor at 15 kg / hr, depressurized to 10.13 kPa to reduce residual lactide, and the poly L-lactic acid resin after chipping it again is The weight average molecular weight was 120,000, the molecular weight dispersion was 1.8, and the lactide content was 0.005 wt%.
In the same synthetic experiment, D-lactide was used to polymerize a poly-D-lactic acid resin having a weight average molecular weight of 120,000, a molecular weight dispersion of 1.8, and a lactide content of 0.005 wt%.

[Examples 1-3 and Comparative Examples 1-4]
After mixing the phosphoric acid ester metal salt in the amount shown in the table in 100 parts by weight of a mixture of poly L-lactic acid and poly D-lactic acid, which were prepared in the foregoing synthesis example and dried at 120 ° C. for 5 hours, 1/1 weight ratio, Melted and kneaded with a twin-screw extruder at the indicated temperature, melt-extruded into a film with a thickness of 360 μm at a casting speed of 40 m / min at a die temperature of 260 ° C., and mirror-cooled by electrostatic casting using a platinum-coated linear electrode The drum surface was adhered and solidified. The unstretched film was further stretched at 80 ° C., three times in the longitudinal direction, three times in the transverse direction, and heat-set at 190 ° C. to obtain a biaxially stretched film having a thickness of 40 μm.
In all experiments, the melt stability was 80% or more and passed. The results are listed in Table 1.
As the phosphate metal salt, “ADEKA STAB (registered trademark)” NA-21 manufactured by ADEKA Corporation, “ADEKA STAB (registered trademark)” NA-11 manufactured by ADEKA Corporation, “ADK STAB (registered trademark)” NA-11 manufactured by ADEKA Corporation, and the like. And (NA-11 (*)) described above were used after pulverizing and removing the number of particles exceeding 10 μm.

  The polylactic acid film of the present invention is a film having good transparency and heat resistance, and is suitable for optical applications by taking advantage of good transparency, such as a film for capacitors, a film for printers, and a film for ceramic liners.

Claims (10)

A polylactic acid (B) component containing 0 to 10 mol% of a component other than the L-lactic acid unit as a main component, and a component other than the D-lactic acid unit as a main component containing the D-lactic acid unit as 0 to 0 Adeka Stub (registered trademark) NA-71 was further added to polylactic acid (A ) obtained by melt-kneading the polylactic acid (C) component containing 10 mol% with a weight ratio of (B / C) = 10/90 to 90/10. , ADK STAB (R) NA-21, of at least one phosphoric ester metal salt of polylactic acid (a) consists of 0.01 per 100 parts by weight of Te Ko溶 melting extrusion is contained such that the 5 parts by weight selected from A polylactic acid film having a stereocomplex crystallinity (S) of 98% or more and a haze of 1% or less represented by the following formula measured with a differential scanning calorimeter (DSC measurement).
[Equation 1]
S = {ΔHmsc / (ΔHmsc + ΔHmh)} × 100 (1)
(Wherein, △ Hm h crystalline low melting enthalpy of fusion melt peak below the melting peak temperature 190 ℃, ΔHmsc melting refractory melting peak crystal melting peak temperature is above 190 ° C. by DSC measurements at D SC Measurement Represents enthalpy.)   The polylactic acid film according to claim 1, wherein the crystal melting peak in DSC measurement is a single peak substantially consisting of only a peak having a peak temperature of 190 ° C. or higher.   The polylactic acid film according to claim 1, wherein the polylactic acid film is stretched in a uniaxial direction by 2 to 7 times.   The polylactic acid film according to claim 1 or 2, which has been stretched 4 to 50 times in area magnification. Carboxyl end group concentration of from 0 10 eq / ton, polylactic acid film according to any one of claims 1 or al 4. The weight average molecular weight of polylactic acid (A) is 80,000 from 250,000, polylactic acid film according to any one of claims 1, 4, and 5. A polylactic acid (B) component containing 0 to 10 mol% of a component other than the L-lactic acid unit as a main component, and a component other than the D-lactic acid unit as a main component containing the D-lactic acid unit as 0 to 0 The polylactic acid (C) component containing 10 mol% is melt-kneaded at a weight ratio of (B / C) = 10/90 to 90/10, and the polylactic acid (A ) is further added to ADK STAB (registered trademark) NA -71, after contained so that the ADK STAB (R) NA-21, of at least one phosphoric ester metal salt of polylactic acid (a) 0.01 to 5 parts by weight per 100 parts by weight selected from, tree butter temperature, characterized in that the melt-extruded in a range of (Tmsc + 20) and a (Tmsc + 50) (℃) , the production method of the polylactic acid film according to claim 1.
(Here, Tmsc represents a peak temperature of a high melting point crystal melting peak having a peak temperature of 190 ° C. or higher in DSC measurement.) The manufacturing method according to claim 7, wherein after the melt extrusion, the film is uniaxially or biaxially stretched and then heat-treated in a temperature range of (Tmh to Tmsc).
(Here, Tmsc represents a high melting point crystal melting peak temperature having a crystal melting peak temperature of 190 ° C. or higher by DSC measurement, and Tmh represents a low melting point crystal melting peak temperature having a crystal melting peak temperature of 190 ° C. or less by DSC measurement.) The optical polylactic acid film according to any one of claims 1 to 6 . The polylactic acid film for packaging according to any one of claims 1 to 6 .