JP2011140666A - Polylactic acid-based stretched film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid-based stretched film being biodegradable and excellent in transparency and heat resistance. <P>SOLUTION: The polylactic acid-based stretched film is made of a polylactic acid-based composition including poly-L-lactic acid and poly-D-lactic acid, and a peak ratio between a peak height (peak 1) of a maximum endothermic peak in endothermic peaks within a temperature range of 150-200°C and a peak height (peak 2) of a maximum endothermic peak in endothermic peaks within a temperature range of 205-240°C in a DSC measurement, namely the ratio of (peak 1)/(peak 2), is not more than 0.2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a stretched polylactic acid film having biodegradability and excellent transparency and heat resistance.

  In order to facilitate the disposal of plastic films, biodegradable films have attracted attention and various films have been developed. The biodegradable film is subject to hydrolysis and biodegradation in soil and water, gradually breaking down and decomposing the film, and finally changing to a harmless degradation product by the action of microorganisms. As such a film, a film formed from an aromatic polyester resin, an aliphatic polyester resin such as polylactic acid or polybutylene succinate, polyvinyl alcohol, cellulose acetate, starch or the like is known.

  A biaxially stretched film made of polylactic acid, which is one of such biodegradable resins, has begun to be used as a packaging film because of its excellent transparency, but it is inferior in heat resistance as it is.

On the other hand, as a method for improving the heat resistance of polylactic acid, many methods for forming a stereocomplex by blending poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA) have been proposed (for example, Patent Document 1, Patent Document 2, Non-Patent Document 1).
However, even if a composition obtained by simply melt-kneading PLLA and PDLA is formed into a film, a stereocomplex is not easily formed, and the formed film is brittle, although the heat resistance is improved, It is difficult to use as a packaging film.

Japanese Patent Laid-Open No. 9-25400 JP 2000-17164 A

Macromolecules, 20, 904 (1987)

  An object of this invention is to develop the polylactic acid-type stretched film which has biodegradability, and is excellent in transparency and heat resistance.

  The present invention comprises a polylactic acid-based composition containing poly-L-lactic acid and poly-D-lactic acid, and has a peak endothermic peak height (peak 1) in the range of 150 to 200 ° C. in DSC measurement. And a peak ratio (peak 1 / peak 2) between the maximum endothermic peak height (peak 2) of the endothermic peak in the range of 205 to 240 ° C. is 0.2 or less, and is a polylactic acid stretch A film is provided.

  The polylactic acid-based stretched film of the present invention can be used up to 180 ° C., while the usable temperature of the conventional polylactic acid biaxially stretched film is up to 140 ° C., and the biodegradability is not impaired and is transparent. Also excellent.

1 is a chart showing a DSC measurement chart of the first temperature increase of the stretched film of Example 1. FIG. 2 is a chart showing a DSC measurement chart of the first temperature drop of the stretched film of Example 1. FIG. 3 is a chart showing a DSC measurement chart of the second temperature increase of the stretched film of Example 1. FIG. 4 is a diagram showing a DSC measurement chart of the first temperature increase of the stretched film of Comparative Example 1. FIG. FIG. 5 is a diagram showing a DSC measurement chart of the first temperature drop of the stretched film of Comparative Example 1. 6 is a chart showing a DSC measurement chart of the second temperature increase of the stretched film of Comparative Example 1. FIG. 7 is a chart showing a DSC measurement chart of the first temperature drop of a sheet (unstretched) made of the polylactic acid-based composition of Example 1. FIG. FIG. 8 is a diagram showing a DSC measurement chart of the second temperature increase of a sheet (unstretched) made of the polylactic acid-based composition of Example 1. FIG. 9 is a chart showing a DSC measurement chart of the first temperature drop of a sheet (unstretched) made of the polylactic acid-based composition of Comparative Example 1. FIG. 10 is a diagram showing a DSC measurement chart of the second temperature rise of a sheet (unstretched) made of the polylactic acid-based composition of Comparative Example 1. FIG. 11 shows the results of wide-angle X-ray diffraction measurement of the stretched film of Example 1. FIG. 12 is a view showing a wide-angle X-ray diffraction measurement result of the stretched film of Comparative Example 1. FIG. 13 is a chart showing a DSC measurement chart of the first temperature rise of the stretched film of Example 2. 14 is a chart showing a DSC measurement chart of the first temperature drop of the stretched film of Example 2. FIG. FIG. 15 is a chart showing a DSC measurement chart of the second temperature increase of the stretched film of Example 2. 16 is a chart showing a DSC measurement chart of the first temperature drop of a sheet (unstretched) made of the polylactic acid-based composition of Example 2. FIG. FIG. 17 is a diagram showing a DSC measurement chart of second temperature increase of a sheet (unstretched) made of the polylactic acid composition of Example 2. 18 is a chart showing a DSC measurement chart of first temperature increase of the stretched film of Example 3. FIG. 19 is a chart showing a DSC measurement chart of the first temperature drop of the stretched film of Example 3. FIG. FIG. 20 is a diagram showing a DSC measurement chart of the second temperature increase of the stretched film of Example 3. 21 is a chart showing a DSC measurement chart of the first temperature drop of a sheet (unstretched) made of the polylactic acid-based composition of Example 3. FIG. FIG. 22 is a diagram showing a DSC measurement chart of the second temperature increase of a sheet (unstretched) made of the polylactic acid-based composition of Example 3. FIG. 23 is a diagram showing a DSC measurement chart of the first temperature increase of the stretched film of Example 4. FIG. 24 is a chart showing a DSC measurement chart of the first temperature drop of the stretched film of Example 4. 25 is a chart showing a DSC measurement chart of second temperature increase of the stretched film of Example 4. FIG. 26 is a chart showing a DSC measurement chart of the first temperature drop of a sheet (unstretched) made of the polylactic acid composition of Example 4. FIG. FIG. 27 is a chart showing a DSC measurement chart of second temperature increase of a sheet (unstretched) made of the polylactic acid-based composition of Example 4. 28 is a chart showing a DSC measurement chart of the first temperature increase of the stretched film of Example 5. FIG. FIG. 29 is a chart showing a DSC measurement chart of the first temperature drop of the stretched film of Example 5. 30 is a chart showing a DSC measurement chart of second temperature increase of the stretched film of Example 5. FIG. FIG. 31 is a chart showing a DSC measurement chart of the first temperature drop of a sheet (unstretched) made of the polylactic acid-based composition of Example 5. FIG. 32 is a diagram showing a DSC measurement chart of second temperature increase of a sheet (unstretched) made of the polylactic acid-based composition of Example 5. FIG. 33 is a diagram showing a DSC measurement chart of first temperature increase of the stretched film of Example 6. FIG. 34 is a chart showing a DSC measurement chart of the first temperature drop of the stretched film of Example 6. FIG. 35 is a diagram showing a DSC measurement chart of second temperature increase of the stretched film of Example 6. 36 is a chart showing a DSC measurement chart of the first temperature drop of a sheet (unstretched) made of the polylactic acid-based composition of Example 6. FIG. FIG. 37 is a diagram showing a DSC measurement chart of second temperature increase of a sheet (unstretched) made of the polylactic acid-based composition of Example 6. 38 is a diagram showing a DSC measurement chart of the first temperature increase of the stretched film of Comparative Example 2. FIG. FIG. 39 is a diagram showing a DSC measurement chart of the first temperature drop of the stretched film of Comparative Example 2. 40 is a diagram showing a DSC measurement chart of second temperature increase of the stretched film of Comparative Example 2. FIG. 41 is a chart showing a DSC measurement chart of the first temperature drop of a sheet (unstretched) made of the polylactic acid-based composition of Comparative Example 2. FIG. FIG. 42 is a diagram showing a DSC measurement chart of the second temperature increase of a sheet (unstretched) made of the polylactic acid-based composition of Comparative Example 2. FIG. 43 is a diagram showing a DSC measurement chart of the first temperature increase of the stretched film of Comparative Example 3. FIG. 44 is a diagram showing a DSC measurement chart of the first temperature drop of the stretched film of Comparative Example 3. 45 is a chart showing a DSC measurement chart of second temperature increase of the stretched film of Comparative Example 3. FIG. 46 is a diagram showing a DSC measurement chart of the first temperature drop of a sheet (unstretched) made of the polylactic acid-based composition of Comparative Example 3. FIG. 47 is a diagram showing a DSC measurement chart of second temperature increase of a sheet (unstretched) made of the polylactic acid-based composition of Comparative Example 3. FIG. FIG. 48 is a diagram showing a DSC measurement chart of the first temperature increase of the stretched film of Comparative Example 4. 49 is a chart showing a DSC measurement chart of the first temperature drop of the stretched film of Comparative Example 4. FIG. 50 is a diagram showing a DSC measurement chart of second temperature increase of the stretched film of Comparative Example 4. FIG. 51 is a diagram showing a DSC measurement chart of the first temperature drop of a sheet (unstretched) made of the polylactic acid-based composition of Comparative Example 4. FIG. 52 is a diagram showing a DSC measurement chart of second temperature increase of a sheet (unstretched) made of the polylactic acid-based composition of Comparative Example 4. FIG. 53 is a diagram showing a DSC measurement chart of first temperature increase of a stretched film of Comparative Example 5. FIG. FIG. 54 is a diagram showing a DSC measurement chart of the first temperature drop of the stretched film of Comparative Example 5. 55 is a chart showing a DSC measurement chart of second temperature increase of the stretched film of Comparative Example 5. FIG. FIG. 56 is a diagram showing a DSC measurement chart of the first temperature drop of a sheet (unstretched) made of the polylactic acid-based composition of Comparative Example 5. FIG. 57 is a diagram showing a DSC measurement chart of second temperature increase of a sheet (unstretched) made of the polylactic acid-based composition of Comparative Example 5. 58 is a diagram showing the results of wide-angle X-ray diffraction measurement of the stretched film of Example 2. FIG. FIG. 59 shows the results of wide-angle X-ray diffraction measurement of the stretched film of Example 3. FIG. 60 shows the results of wide-angle X-ray diffraction measurement of the stretched film of Example 4. 61 is a view showing a wide-angle X-ray diffraction measurement result of the stretched film of Example 5. FIG. FIG. 62 is a view showing a wide-angle X-ray diffraction measurement result of the stretched film of Example 6. FIG. 63 is a view showing a wide-angle X-ray diffraction measurement result of the stretched film of Comparative Example 2. FIG. 64 is a view showing a wide-angle X-ray diffraction measurement result of the stretched film of Comparative Example 3. 65 is a view showing a wide-angle X-ray diffraction measurement result of the stretched film of Comparative Example 4. FIG. 66 is a view showing a wide-angle X-ray diffraction measurement result of the stretched film of Comparative Example 5. FIG. 67 is a chart showing DSC measurement chart of first temperature increase of the stretched film of Example 10. FIG. 68 is a chart showing DSC measurement chart of first temperature drop of the stretched film of Example 10. FIG. FIG. 69 is a chart showing a DSC measurement chart of second temperature rise of the stretched film of Example 10. 70 is a chart showing DSC measurement chart of first temperature increase of the stretched film of Example 11. FIG. 71 is a chart showing DSC measurement chart of first temperature drop of the stretched film of Example 11. FIG. 72 is a chart showing DSC measurement chart of second temperature increase of the stretched film of Example 11. FIG. 73 is a chart showing DSC measurement chart of first temperature increase of the stretched film of Example 12. FIG. 74 is a chart showing DSC measurement chart of first temperature drop of the stretched film of Example 12. FIG. 75 is a chart showing DSC measurement chart of second temperature increase of the stretched film of Example 12. FIG. 76 is a chart showing DSC measurement chart of first temperature increase of a stretched film of Example 13. FIG. 77 is a chart showing DSC measurement chart of first temperature drop of the stretched film of Example 13. FIG. 78 is a chart showing DSC measurement chart of second temperature increase of the stretched film of Example 13. FIG. FIG. 79 is a chart showing DSC measurement chart of first temperature increase of the stretched film of Example 14. 80 is a chart showing DSC measurement chart of first temperature drop of the stretched film of Example 14. FIG. FIG. 81 is a chart showing DSC measurement chart of second temperature increase of the stretched film of Example 14. 82 is a view showing a wide-angle X-ray diffraction measurement result of the stretched film of Example 10. FIG. FIG. 83 is a view showing a wide-angle X-ray diffraction measurement result of the stretched film of Example 11. 84 is a view showing a wide-angle X-ray diffraction measurement result of the stretched film of Example 12. FIG. 85 is a view showing a wide-angle X-ray diffraction measurement result of the stretched film of Example 13. FIG. FIG. 86 is a view showing a wide-angle X-ray diffraction measurement result of the stretched film of Example 14.

<Poly-L-lactic acid>
Poly-L-lactic acid (PLLA), which is one component of the polylactic acid composition according to the present invention, is a polymer containing L-lactic acid as a main constituent, preferably 95 mol% or more. A polymer having an L-lactic acid content of less than 95 mol% has a heat resistance of a stretched film obtained by stretching a polylactic acid-based composition obtained by melt-kneading with poly-D-lactic acid (PDLA) described later. May be inferior.

The molecular weight of PLLA is not particularly limited as long as the polylactic acid-based composition mixed with poly-D-lactic acid described later has formability as a layer such as a film. Usually, the weight average molecular weight (Mw) is 6,000 to 300. Poly-L lactic acid in the range of 10,000, preferably 6,000 to 2,000,000 is suitable. If the weight average molecular weight is less than 6,000, the strength of the resulting stretched film may be inferior. On the other hand, if it exceeds 3 million, the melt viscosity is large and the film processability may be inferior.
<Poly-D-lactic acid>
Poly-D-lactic acid (PDLA), which is one component of the polylactic acid composition layer according to the present invention, is a polymer containing D-lactic acid as a main constituent, preferably 95 mol% or more. A polymer having a D-lactic acid content of less than 95 mol% may be inferior in heat resistance of a stretched film obtained by stretching a polylactic acid-based composition obtained by melt-kneading with the poly-L-lactic acid described above. is there.

  The molecular weight of PDLA is not particularly limited as long as the polylactic acid composition mixed with the aforementioned PLLA has formability as a film. Usually, the weight average molecular weight (Mw) is 6,000 to 3,000,000, preferably 6,000 to Poly-D lactic acid in the range of 2 million is preferred. If the weight average molecular weight is less than 6,000, the strength of the resulting stretched film may be inferior. On the other hand, if it exceeds 3 million, the melt viscosity is large and the film processability may be inferior.

In the present invention, PLLA and PDLA contain a small amount of other copolymer components such as polycarboxylic acid or ester thereof, polyhydric alcohol, hydroxycarboxylic acid, lactone, etc. within the range not impairing the object of the present invention. It may be polymerized. Specific examples of the polyvalent carboxylic acid include succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, suberic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, sebacic acid, diglycolic acid, ketopimelic acid, Examples thereof include aliphatic dicarboxylic acids such as malonic acid and methylmalonic acid, and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid.
Specific examples of the polyvalent carboxylic acid ester include dimethyl succinate, diethyl succinate, dimethyl glutarate, diethyl glutarate, dimethyl adipate, diethyl adipate, dimethyl pimelate, dimethyl azelate, and dimethyl suberate. , Aliphatic dicarboxylic acid diesters such as diethyl suberate, dimethyl sebacate, diethyl sebacate, dimethyl decanedicarboxylate, dimethyl dodecanedicarboxylate, dimethyl diglycolate, dimethyl ketopimelate, dimethyl malonate and dimethyl methylmalonate, and terephthalic acid And aromatic dicarboxylic acid diesters such as dimethyl and dimethyl isophthalate.
Specific examples of the polyhydric alcohol include ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,3-butanediol, 2-methyl-propanediol, and 1,4-butanediol. , Neopentyl glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, dodecamethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, dipropylene glycol, triethylene glycol , Tetraethylene glycol, pentaethylene glycol, polyethylene glycol having a molecular weight of 1000 or less, and the like.
Specific examples of the hydroxycarboxylic acid include glycolic acid, 2-methyllactic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, Examples include 2-hydroxy-2-methylbutyric acid, 2-hydroxy-3-methylbutyric acid, hydroxypivalic acid, hydroxyisocaproic acid, and hydroxycaproic acid. Specific examples of lactones include β-propiolactone, β-butyrolactone, γ-butyrolactone, β or γ-valerolactone, δ-valerolactone, δ-caprolactone, ε-caprolactone, and 4-methylcaprolactone. Various methylated caprolactones such as 3,5,5-trimethylcaprolactone and 3,3,5-trimethylcaprolactone; cyclic monomeric esters of hydroxycarboxylic acids such as β-methyl-δ-valerolactone, enanthlactone and laurolactone A cyclic dimer ester of the above hydroxycarboxylic acid such as glycolide, L-lactide, D-lactide and the like.
Further, PLLA and PDLA according to the present invention may each contain a small amount of D-lactic acid or L-lactic acid as long as it is within the above range.

<Polylactic acid-based stretched film>
The stretched polylactic acid film of the present invention comprises a polylactic acid-based composition containing the poly-L-lactic acid and poly-D-lactic acid, and has a maximum endothermic peak of 150 to 200 ° C. in the DSC measurement. The peak ratio (peak 1 / peak 2) between the peak height (peak 1) and the peak endothermic peak height (peak 2) of the endothermic peak in the range of 205-240 ° C. is 0.2 or less, preferably 0 1. A polylactic acid-based stretched film characterized by being 1 or less.

  In addition to the above characteristics, the polylactic acid-based stretched film of the present invention has an endothermic peak endothermic amount (ΔHm) in the range of 205 to 240 ° C. of 40 J / g or more, more preferably 50 J / g or more. After measuring the endothermic peak, the calorific value (ΔHc) when the temperature is lowered is 40 J / g or more, more preferably 50 J / g or more.

In addition to the above characteristics, the polylactic acid-based stretched film of the present invention has a total sum of peak areas (S _SC ) in the vicinity of 12 °, 21 ° and 24 ° of wide angle X-ray measurement of 20% or more with respect to the entire area. The total sum of the peak areas (S _PL ) in the vicinity of 25% or more and 2θ of around 17 degrees and 19 degrees (S _PL ) is 5% or less, preferably 3% or less.
In such wide-angle X-ray measurement, peaks around 2 ° of 17 ° and 19 ° are peaks based on PLLA and PDLA crystals (P _PL ), and peaks around 12 °, 21 °, and 24 ° are the same for PLLA and PDLA. It is a peak ( _PSC ) based on crystal of so-called stereocomplex crystallized. The diffraction peak (2θ) by wide-angle X-ray in the present invention is the angle (degree) of the diffraction peak detected and measured by using an X-ray diffractometer (automatic X-ray diffractometer RINT-2200 or RINT-2500 manufactured by Rigaku Corporation). ). Each diffraction peak area based on a crystal is defined as a total area (total area) of 10 to 30 degrees of diffraction angle (2θ) surrounded by the base line (intensity; 0 cps) of the recording paper and the X-ray diffraction intensity curve. Cut out the areas of diffraction peaks (2θ) around 17 degrees and 19 degrees for (S _PL ), and the diffraction peaks (2θ) around 12 degrees, 21 degrees and 24 degrees for (S _SC ) from the recording paper. It was calculated by measuring its weight. Moreover, the broad part resulting from an amorphous part was made into (amorphous part). When measuring (S _PL ) and (S _SC ), the diffraction curve associated with the amorphous portion was used as a baseline and the portion above it was measured. In addition, when there exists air scattering, it is contained in the broad part resulting from an amorphous part.

  The heat melting characteristics of the polylactic acid-based stretched film in the present invention were measured using a Q100 manufactured by TA Instruments Inc. as a DSC (Differential Scanning Calorimeter), and approximately 5 mg of a sample was precisely weighed, and JIS K 7121 and JIS K In accordance with 7122, the DSC curve was obtained by raising the temperature from 0 ° C. to 250 ° C. at a heating rate of 10 ° C./min under the condition of nitrogen gas inflow rate: 50 ml / min. From the melting point (Tm) of the stretched film, the endothermic amount (ΔHm) of the endothermic peak in the range of 205 to 240 ° C., the peak height (peak 1) of the maximum endothermic peak of the endothermic peak in the range of 150 to 200 ° C. Obtain the peak ratio (peak 1 / peak 2) to the peak height (peak 2) of the endothermic peak in the range of 205-240 ° C. and maintain it at 250 ° C. for 10 minutes. Thereafter, the cooling rate is 10 ° C./min, and the temperature is lowered to 0 ° C. for crystallization to obtain a DSC curve at the time of cooling. From the obtained DSC curve, the calorific value (Hc) at the time of crystallization of the stretched film is obtained. Asked.

  In addition, the peak height was calculated | required by the height from the base line obtained by connecting the base line near 65 to 75 degreeC and the base line near 240 to 250 degreeC.

  The thickness of the stretched polylactic acid film of the present invention is usually in the range of 5 to 500 μm, preferably 10 to 100 μm.

The polylactic acid-based stretched film of the present invention may be subjected to primer coating, corona treatment, plasma treatment, flame treatment, or the like, as necessary, in order to improve the adhesion with other layers or printing layers.
The polylactic acid-based stretched film of the present invention may be laminated with other base materials depending on the application. Other substrates include, for example, polyolefins such as polyethylene, polypropylene, polybutene and polymethylpentene, polyesters such as polyethylene terephthalate and polycarbonate, nylon, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, and ethylene / vinyl alcohol. Polymer, polymethyl methacrylate, ethylene / vinyl acetate copolymer, polylactic acid, film made of thermoplastic resin such as biodegradable polyester such as aliphatic polyester, sheet, cup, tray, or foam thereof, or Glass, metal, aluminum foil, paper, etc. are mentioned. The film made of the thermoplastic resin may be unstretched or may be a uniaxial or biaxially stretched film. Of course, the substrate may be a single layer or two or more layers.

<Polylactic acid-based composition>
In order to obtain a polylactic acid-based stretched film having the above characteristics of the present invention, a polylactic acid-based composition having the following heat melting characteristics is used as a polylactic acid-based composition containing poly-L-lactic acid and poly-D-lactic acid. It is preferable to prepare and stretch.

The polylactic acid composition according to the present invention preferably has a calorific value (ΔHc) of 20 J when the temperature is lowered after the polylactic acid composition is melted at 250 ° C. for 10 minutes (at the first temperature drop) in DSC measurement. It is desirable to have thermal characteristics that are greater than / g.
Furthermore, the polylactic acid-based composition according to the present invention was measured at the second temperature increase of the DSC (after 10 minutes at 250 ° C., the temperature was decreased at 10 ° C./minute, and then increased again from 0 ° C. at 10 ° C./minute. Of the endothermic peak in the range of 150 to 200 ° C. of the DSC curve obtained at (temperature) (peak 10) and the peak height of the endothermic peak of the endothermic peak in the range of 205 to 240 ° C. It is desirable that the peak ratio of (Peak 20) (Peak 10 / Peak 20) is preferably 0.5 or less, more preferably 0.3 or less, and particularly preferably 0.2 or less. This is presumably because this composition selectively forms stereocomplex crystals.
If the peak ratio (peak 10 / peak 20) is greater than 0.5, the amount of PLLA and PDLA single crystals formed after crystallization is large, and poly-L-lactic acid and poly-D-lactic acid are not sufficiently kneaded. There is a fear. A composition having a peak ratio (Peak 10 / Peak 20) greater than 0.5 has a large amount of α-crystals (PLLA or PDLA single crystal) formed after crystallization. .
The polylactic acid-based composition according to the present invention preferably has an endothermic amount (ΔHm) of an endothermic peak of 205 to 240 ° C. at the time of the second DSC temperature increase of 35 J / g or more.
The heat melting characteristics of the polylactic acid-based composition according to the present invention are the same as the methods for determining the heat-melting characteristics of the above-mentioned stretched polylactic acid film, and DSA (Differential Scanning Calorimeter) is used. About 100 mg of a sample was precisely weighed using Q100 manufactured by Ment Co., Ltd., and determined according to JIS K7121 and JIS K7122. In addition, the heat melting characteristic of the polylactic acid-type composition calculated | required the characteristic at the time of temperature fall and the time of the 2nd temperature rise.

  The polylactic acid composition according to the present invention is preferably 25 to 75 parts by weight of the PLLA, more preferably 35 to 65 parts by weight, particularly preferably 45 to 55 parts by weight, and particularly preferably 47 to 53 parts by weight. PDLA is preferably composed of 75 to 25 parts by weight, more preferably 65 to 35 parts by weight, particularly preferably 55 to 45 parts by weight, and most preferably 53 to 47 parts by weight (PLLA + PDLA = 100 parts by weight). That is, it is prepared.

  In the polylactic acid-based composition according to the present invention, the poly-L-lactic acid and the poly-D-lactic acid each have a weight average molecular weight in the range of 6,000 to 3,000,000, and It is desirable to prepare by kneading from poly-L-lactic acid and poly-D-lactic acid, each having a weight average molecular weight of 30,000 to 2,000,000.

The polylactic acid composition according to the present invention can be obtained, for example, by melt-kneading these PLLA and PDLA at 230 to 260 ° C. with a twin-screw extruder, twin-screw kneader, Banbury mixer, plast mill or the like. it can.
Even if a composition having an amount of PLLA outside the above range is kneaded by the above-described method, a film formed by stretching the obtained composition contains α-crystals and may have insufficient heat resistance.
The reason why the polylactic acid composition according to the present invention is excellent in heat resistance is that the composition forms a stereocomplex structure, and the stereocomplex structure is composed of equal amounts of PLLA and PDLA. .
In order to obtain the polylactic acid composition according to the present invention, the temperature at which PLLA and PDLA are melt-kneaded is preferably 230 to 260 ° C, more preferably 235 to 255 ° C. If the melt kneading temperature is lower than 230 ° C, the stereocomplex structure may be unmelted, and if it is higher than 260 ° C, polylactic acid may be decomposed.

  Moreover, when preparing the polylactic acid-type composition concerning this invention, it is desirable to melt-knead PLLA and PDLA fully. The melt-kneading time is usually 5 minutes or longer, although it depends on the melt-kneader used. The longer the melt kneading time of PLLA and PDLA is, for example, 20 minutes or more, or 30 minutes or more, the resulting polylactic acid-based composition has a temperature of 205 to 240 at the second temperature increase of DSC. The endothermic amount (ΔHm) of the endothermic peak at 45 ° C. is 45 J / g or more, or 50 J / g or more, and the endothermic amount of the endothermic peak in the range of 150 to 200 ° C. is 3.5 J / g or less, or 0 J / g, The steric complex can be crystallized more quickly, and a polylactic acid-based composition in which a single crystal (α crystal) of PLLA or PDLA is difficult to form can be obtained, and the clarity of the resulting polylactic acid-based stretched film is increased.

  The polylactic acid-based composition according to the present invention is considered to be difficult to produce a single crystal (α crystal) of PLLA or PDLA because the stereocomplex is rapidly crystallized and the stereocomplex crystallizable region is large.

  As described above, the polylactic acid-based composition according to the present invention has a peak due to crystallization (a calorific value ΔHc) of 20 J when measured by DSC at a temperature drop after 10 minutes at 250 ° C. (10 ° C./min). When it is at least / g, crystallization of the polylactic acid-based composition occurs rapidly.

  On the other hand, if the calorific value due to crystallization is less than 20 J / g, the crystallization rate is low and the kneading may not be sufficient.

  The weight average molecular weight of the polylactic acid composition according to the present invention is not particularly limited. However, the polylactic acid composition according to the present invention preferably has a weight average molecular weight in the range of 10,000 to 1,500,000, and more preferably in the range of 50,000 to 500,000. If the weight average molecular weight deviates from the above range to the polymer side, stereocomplexation may not be sufficient and heat resistance may not be obtained, and if it deviates to the low molecular side, the strength of the polylactic acid composition layer obtained is sufficient There is a possibility that it is not.

<Method for producing a polylactic acid-based stretched film>
The polylactic acid-based stretched film of the present invention is a film or sheet obtained by extrusion molding using the polylactic acid-based composition containing poly-L-lactic acid and poly-D-lactic acid, preferably in one direction. A stretched film having excellent heat resistance and transparency can be obtained by stretching at least twice, more preferably 2 to 12 times, and even more preferably 3 to 6 times. The upper limit of the stretching ratio is not particularly limited as long as it can be stretched. However, if it exceeds 12 times, the film may be broken or the film may not be stably stretched.

Further, the film or sheet obtained by extrusion molding is preferably at least 2 times in the vertical direction and at least 2 times in the horizontal direction, more preferably 2 to 7 times in the vertical direction and 2 to 7 times in the horizontal direction, still more preferably. Is stretched 2.5 to 5 times in the longitudinal direction and 2.5 to 5 times in the lateral direction, whereby a stretched film (biaxially stretched film) having excellent heat resistance and transparency is obtained. The upper limit of the stretching ratio is not particularly limited as long as it can be stretched. However, if it exceeds 7 times, the film may be broken and may not be stably stretched.
Moreover, in the range which can be extended | stretched favorably, it exists in the tendency for the rigidity and heat resistance of the film obtained to increase, so that it is oriented strongly so that a draw ratio is high.
Further, biaxial stretching may be performed in two stages, MD → TD → MD, to increase the degree of orientation in the MD direction, and to increase the rigidity and heat resistance in the MD direction. Naturally, conversely, it may be stretched in two stages in the TD direction.

  After stretching, the polylactic acid-based stretched film of the present invention is preferably 140 to 220 ° C, more preferably 150 to 200 ° C, preferably 1 second or more, more preferably 3 to 60 seconds, Heat resistance is improved.

  EXAMPLES Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples unless it exceeds the gist.

The polylactic acid used in Examples, Comparative Examples and Reference Examples is as follows.
(A) Poly-L-lactic acid (PLLA-1):
D form amount: 1.9% Mw: 222,000 (g / mol), Tm: 163 ° C.
(B) Poly-L-lactic acid (manufactured by PURAC: PLLA-2):
D body amount: 0.0% Mw: 395,000 (g / mol), Tm: 184 ° C,
Inherent viscosity (chloroform, 25 ° C., 0.1 g / dl): 3.10 (dl / g)
(C) Poly-L-lactic acid (manufactured by PURAC: PLLA-3):
D body amount: 0.0% Mw: 14.3 million (g / mol), Tm: 186 ° C.,
Inherent viscosity (chloroform, 25 ° C., 0.1 g / dl): 7.11 (dl / g)
(2) Poly-D-lactic acid (manufactured by PURAC: PDLA-1):
D body amount: 100.0% Mw: 298,000 (g / mol), Tm: 176 ° C,
Inherent viscosity (chloroform, 25 ° C., 0.1 g / dl): 2.46 (dl / g)
(E) Poly-D-lactic acid (manufactured by PURAC: PDLA-2):
D body amount: 100.0% Mw: 1.35 million (g / mol), Tm: 180 ° C.,
Inherent viscosity (chloroform, 25 ° C., 0.1 g / dl): 7.04 (dl / g)

  The measuring method in the present invention is as follows.

(1-1) Weight average molecular weight (Mw)
The poly-L-lactic acid and poly-D-lactic acid of (i) to (e) were measured by the following method.
To 20 mg of the sample, 10 ml of GPC eluent was added, and the mixture was allowed to stand overnight and then gently stirred by hand. This solution was filtered through an amphiphilic 0.45 μm-PTFE filter (ADVANTEC DISMIC-25HP045AN) to obtain a GPC sample solution.
Measuring device; Shodex GPC SYSTEM-21
Analysis device; data analysis program: SIC480 data station II
Detector: Differential refraction detector (RI)
Column; Shodex GPC K-G + K-806L + K-806L
Column temperature; 40 ° C. Eluent; Chloroform flow rate; 1.0 ml / min Injection volume; 200 μL molecular weight calibration; Monodisperse polystyrene

(1-2) Weight average molecular weight (Mw)
A polylactic acid composition obtained by melt-kneading poly-L-lactic acid and poly-D-lactic acid was measured by the following method.
A 20 mg sample was dissolved in the mobile phase (concentration 0.5%), and filtered through a 0.45 μm hydrophilic PTFE filter (Millex-LH; Nihon Millipore) to obtain a GPC sample solution.
Column; 2 PL HFIPgel (300 × 7.5 mm) (Polymer laboratories)
Column temperature; 40 ° C. mobile phase; HFIP + 5 mM TFANa flow rate; 1.0 ml / min detection; RI
Injection volume: 50 μL
Measuring device: 510 high pressure pump, U6K
Water injection system, 410 differential refractometer (Japan Waters)
Molecular weight calibration; monodisperse PMMA (Easy Cal PM-1; Polymer laboratories)
(2) DSC measurement It measured by the method of the said description.
(3) Transparency The haze (HZ) and parallel light ray transmittance (PT) of the film were measured using a haze meter 300A manufactured by Nippon Denshoku Industries Co., Ltd.
(4) Surface roughness The center surface average roughness (SRa) of the film surface was measured using a three-dimensional surface roughness measuring instrument SE-30K manufactured by Kosaka Laboratory.
(5) Tensile test A strip-shaped test piece (length: 50 or 150 mm, width: 15 mm) is sampled from the film in the MD direction and TD direction, respectively, and a tensile tester (Orientec Tensilon Universal Tester RTC) is obtained. -1225), a tensile test was performed at a distance between chucks of 20 mm or 100 mm, a crosshead speed of 300 mm / min (however, Young's modulus was measured at 5 mm / min), and tensile strength (MPa), Elongation (%) and Young's modulus (MPa) were determined.
However, in Example 1 and Comparative Example 1, the distance between chucks was 100 mm, but in Examples 2 to 6 and Comparative Examples 2 to 6, the distance between chucks was 20 mm.
(6) Heat resistance A test piece with a width of 4 mm is cut out from the film using a thermal analyzer (thermal / application / strain measuring device TMA / SS120 manufactured by Seiko Instruments Inc.), and a load of 0.25 MPa is applied to the test piece with a gap of 5 mm between chucks. The temperature was raised from 100 ° C. (starting temperature) at 5 ° C./min, and the deformation (elongation or shrinkage) of the test piece at each temperature was measured.
(7) Wide-angle X-ray measurement Measurement of Example 1 and Comparative Example 1 Measuring device: X-ray diffractometer (Rigaku Corporation automatic X-ray diffractometer RINT-2200)
Reflective X-ray target; Cu
K-α output: 40 kV x 40 mA
Rotation angle: 4.0 degrees / minute Step: 0.02 degrees Scanning range: 10-30 degrees Measurement of Examples 2-6, Examples 10-14 and Comparative Examples 2-5 Measuring apparatus: X-ray diffractometer (stock) Rigaku Automatic X-ray Diffractometer RINT-2500)
Transmission X-ray target: Cu
K-α output: 50 kV x 300 mA
Rotation angle: 2.0 degrees / minute Step: 0.01 degrees Scanning range: 5 to 30 degrees (8) Moisture permeability (water vapor permeability)
It calculated | required based on JISZ0208. The film was collected to make a bag with a surface area of about 100 cm ² , and after putting an appropriate amount of calcium chloride, it was sealed. This was left in an atmosphere of 40 ° C. and 90% RH (relative humidity) for 3 days, and the moisture permeability (water vapor permeability) was determined from the weight increase.
(9) Oxygen permeability Based on JIS K7126, the oxygen permeability was measured using an oxygen permeation measuring instrument (manufactured by MOCON, OXTRAN2 / 21 ML) under the conditions of 20 ° C. and 0% RH (relative humidity).
(10) Plane orientation degree of film It measured at 23 degreeC using Abbe refractometer DR-M2 type | mold made by Atago Co., Ltd.
Example 1
PLLA-1: PDLA-2 was weighed at a ratio of 50:50 (parts by weight), and melted and kneaded at a melting temperature of 250 ° C. and a kneading time of 1 minute using a twin-screw kneading extruder. After obtaining the product, a sheet made of a polylactic acid-based composition having a thickness of about 300 μm was obtained with a T-die sheet molding machine.
This twin-screw kneading extruder has a capacity of 40 kg / h, but the amount of extrusion is about several tens of seconds. Since kneading was insufficient, the kneading time was increased to 6 minutes by reducing the extrusion rate to 7 kg / h.
The heat melting characteristics of the polylactic acid composition were measured by the method described above.
Next, the sheet was stretched in a longitudinal direction by a biaxial stretching machine manufactured by Bruckner; 3 times at 65 ° C., a stretching temperature in the transverse direction; 3 times at 70 ° C., and about 180 ° C. in a tenter. Heat setting was performed for 40 seconds to obtain a polylactic acid-based stretched film. The physical properties of the obtained polylactic acid-based stretched film were measured by the method described above.
The measurement results are shown in Table 1, and the thermal melting characteristics are shown in FIGS.
Comparative Example 1
Instead of PLLA-1 and PDLA-1 used in Example 1, PLLA-1 is used alone, except that heat setting of the biaxially stretched film is performed at 150 ° C. for about 40 seconds, and performed in the same manner as in Example 1. A sheet of PLLA-1 and a biaxially stretched film were obtained.
The measurement results are shown in Table 1, and the thermal melting characteristics are shown in FIGS.

表１から明らかなように、実施例１で得られたポリ乳酸系組成物からなる二軸延伸フィルムは、熱融解特性において、１５０〜２００℃の範囲の吸熱ピーク（吸熱量）は僅かで、２０５〜２４０℃の範囲の吸熱ピークは大きく、吸熱量（ΔＨｍ）も６６．１Ｊ／ｇと多く、降温した際の発熱量（ΔＨｃ）も４９．７Ｊ／ｇある。
また、二軸延伸フィルムの素材となるポリ乳酸系組成物（シート）の熱融解特性は、第１回降温時の発熱量（ΔＨｃ）が２０．３Ｊ／ｇ、第２回昇温時には、１５０〜２００℃の範囲には吸熱ピークはみられず、２０５〜２４０℃の範囲の吸熱ピークの吸熱量（ΔＨｍ）は５１．０Ｊ／ｇである。
さらに、実施例１で得られたポリ乳酸系組成物からなる二軸延伸フィルムは、透明性、耐熱性に優れ、透湿度及び酸素透過度も低く、バリア性能を有し、広角Ｘ線測定における１２度、２１度、２４度近辺のピーク面積（Ｓ_SC）が全体の面積に対して５０．９％と２０％以上であり、かつ２θが１７度、１９度近辺のピーク面積（Ｓ_PL）が全体の面積に対して０．０％と５％以下である。そのため結晶化した部分はステレオコンプレックス構造物となっており、その比率が大きいことが分かる。

As is clear from Table 1, the biaxially stretched film made of the polylactic acid composition obtained in Example 1 has a slight endothermic peak (endothermic amount) in the range of 150 to 200 ° C. in the heat melting characteristics. The endothermic peak in the range of 205 to 240 ° C. is large, the endothermic amount (ΔHm) is as large as 66.1 J / g, and the calorific value (ΔHc) when the temperature is lowered is 49.7 J / g.
The heat melting characteristics of the polylactic acid-based composition (sheet) used as the material for the biaxially stretched film are as follows. The calorific value (ΔHc) at the first temperature drop is 20.3 J / g, and at the second temperature rise, 150 to No endothermic peak is observed in the range of 200 ° C., and the endothermic amount (ΔHm) of the endothermic peak in the range of 205 to 240 ° C. is 51.0 J / g.
Furthermore, the biaxially stretched film made of the polylactic acid-based composition obtained in Example 1 is excellent in transparency and heat resistance, has low moisture permeability and oxygen permeability, has barrier performance, and is used in wide-angle X-ray measurement. The peak areas around 12 degrees, 21 degrees, and 24 degrees (S _SC ) are 50.9% and 20% or more of the entire area, and the peak areas around 2 degrees 17 degrees and 19 degrees (S _PL ) Are 0.0% and 5% or less of the entire area. Therefore, it can be seen that the crystallized portion has a stereo complex structure, and the ratio is large.

On the other hand, the biaxially stretched film made of PLLA-1 obtained in Comparative Example 1 has only an endothermic peak in the range of 150 to 200 ° C, no endothermic peak in the range of 205 to 240 ° C, and exotherm when the temperature is lowered. The amount (ΔHc) is 0.4 J / g, which is smaller than that of the biaxially stretched film made of the polylactic acid composition obtained in Example 1.
In addition, the thermal melting characteristics of PLLA-1 (sheet), which is a material of the biaxially stretched film, has a calorific value (ΔHc) of 0 at the first temperature drop, and a range of 205 to 240 ° C. at the second temperature rise. No endothermic peak was observed, only a peak in the range of 150 to 200 ° C., and the endothermic amount (ΔHm) was 32.1 J / g.
Furthermore, the biaxially stretched film made of PLLA-1 obtained in Comparative Example 1 is excellent in transparency but inferior in heat resistance and barrier performance, and has diffraction peaks of 12 degrees, 21 degrees and 24 degrees in wide angle X-ray measurement. The peak area around S degrees (S _SC ) is 0.0% of the whole area, and 2θ is 17 degrees and the peak area around 19 degrees (S _PL ) is 57.3% of the whole area. It is. Therefore, it can be seen that the crystallized portion does not contain a stereocomplex structure.
Example 2
<Manufacture of press sheet made of polylactic acid-based composition>
PLLA-1: PDLA-2 was weighed at a ratio of 50:50 (parts by weight) at 80 g, and melted for 20 minutes at 250 ° C. and 120 rpm using a Toyo Seiki Laboplast Mill C model (biaxial kneader). A polylactic acid composition was obtained by kneading.
Subsequently, the polylactic acid composition was press-molded to obtain a press sheet made of the polylactic acid composition having a thickness of 500 μm.
<Manufacture of biaxially stretched film>
The press sheet was preheated with 75 ° C. hot air for 60 seconds using a pantograph batch biaxial stretching apparatus (Brookner), and then stretched 3.0 times in the longitudinal and transverse directions at a speed of 2.1 m / min (simultaneous). Biaxially stretched) to obtain a biaxially stretched film having a thickness of about 50 μm.
Next, the obtained biaxially stretched film was fixed to a metal frame with a clip, heat-set (heat treated) at 200 ° C. for 15 minutes, and then sufficiently cooled at room temperature to obtain a polylactic acid-based biaxially stretched film.

The press sheet and polylactic acid biaxially stretched film which consisted of the obtained polylactic acid-type composition were measured by the method of the said description. The measurement results are shown in Table 2.
Example 3
A polylactic acid composition and a polylactic acid biaxially stretched film were obtained in the same manner as in Example 2 except that PLLA-3 was used instead of PLLA-1 used in Example 2.

The press sheet and polylactic acid biaxially stretched film which consisted of the obtained polylactic acid-type composition were measured by the method of the said description.
The measurement results are shown in Table 2.
Example 4
A polylactic acid-based composition was prepared in the same manner as in Example 2 except that PLLA-3 was used instead of PLLA-1 used in Example 2, and PDLA-1 was used instead of PDLA-2 used in Example 2. And the polylactic acid-type biaxially stretched film was obtained.

The press sheet and polylactic acid biaxially stretched film which consisted of the obtained polylactic acid-type composition were measured by the method of the said description.
The measurement results are shown in Table 2.
Example 5
A polylactic acid-based composition and a polylactic acid-based biaxially stretched film were obtained in the same manner as in Example 2 except that PLLA-2 was used instead of PLLA-1 used in Example 2.

The press sheet and polylactic acid biaxially stretched film which consisted of the obtained polylactic acid-type composition were measured by the method of the said description.
The measurement results are shown in Table 2.
Example 6
A polylactic acid-based composition was prepared in the same manner as in Example 2 except that PLLA-2 was used instead of PLLA-1 used in Example 2, and PDLA-1 was used instead of PDLA-2 used in Example 2. And the polylactic acid-type biaxially stretched film was obtained.

The press sheet and polylactic acid biaxially stretched film which consisted of the obtained polylactic acid-type composition were measured by the method of the said description. The measurement results are shown in Table 2.
Comparative Example 2
The composition and the biaxially stretched film were prepared in the same manner as in Example 2, except that the polylactic acid composition used in Example 2 was replaced by a kneaded product obtained by setting the kneading time in the lab plast mill to 3 minutes. Obtained.

The obtained press sheet and biaxially stretched film were measured by the method described above. The measurement results are shown in Table 2.
Comparative Example 3
The composition and the biaxially stretched film were prepared in the same manner as in Example 2 except that the kneaded product obtained by changing the polylactic acid-based composition used in Example 4 to 3 minutes in the lab plast mill was used. Obtained.

The obtained press sheet and biaxially stretched film were measured by the method described above.
The measurement results are shown in Table 2.
Comparative Example 4
The composition and the biaxially stretched film were prepared in the same manner as in Example 2 except that the kneaded material obtained by replacing the polylactic acid-based composition used in Example 6 with a lab plast mill for 3 minutes was used. Obtained.

The obtained press sheet and biaxially stretched film were measured by the method described above.
The measurement results are shown in Table 2.

表２の実施例２〜６に示すように、本発明のポリ乳酸系延伸フィルムはいずれも、ＤＳ

Ｃ測定における１５０〜２００℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク１）と２０５〜２４０℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク２）とのピーク比（ピーク１／ピーク２）が０．０６〜０．１８といずれも０．２以下であり、２０５〜２４０℃の範囲にある吸熱ピークの吸熱量は４５．０〜６２．４Ｊ／ｇといずれも４０J／ｇ以上であり、降温時の発熱量は４６．１〜７１．４Ｊ／ｇといずれも４０J／g以上であり、耐熱性に優れることが分かる。
また、かかる熱融解特性を有するポリ乳酸系延伸フィルムを得るには、ポリ乳酸系組成物の第１回降温時の発熱量が多く、第２回昇温時における１５０〜２００℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク１０）と２０５〜２４０℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク２０）とのピーク比（ピーク１０／ピーク２０）が０．５以下のポリ乳酸系組成物を用いることが好ましいことが分かる。
また実施例２〜６は広角Ｘ線測定における１２度、２１度、２４度近辺のピーク面積（Ｓ_SC）が全体の面積に対して２４〜３２％と２０％以上であり、かつ２θが１７度、１９度近辺のピーク面積（Ｓ_PL）が全体の面積に対して０％と５％以下である。
そのため結晶化した部分はステレオコンプレックス構造物となっており、その比率は大きいことが分かる。
一方、実施例２、４、５、６と同じ混合比を有するポリ−Ｌ−乳酸とポリ−Ｄ−乳酸を用いても、比較例２〜５の延伸フィルムは、ＤＳＣ測定における１５０〜２００℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク１）と２０５〜２４０℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク２）とのピーク比（ピーク１／ピーク２）が０．７３〜１．３９と０．２を超え、耐熱性に劣ることが分かる。
また、比較例２〜４の延伸フィルムの素材として用いた混練物（プレスシート）の第２回昇温時における１５０〜２００℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク１０）と２０５〜２４０℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク２０）とのピーク比（ピーク１０／ピーク２０）は、１．５０〜４．００と０．５を超えている。
また比較例２〜５は広角Ｘ線測定における１２度、２１度、２４度近辺のピーク面積（Ｓ_SC）が全体の面積に対して５〜１９％と２０％未満であり、かつ２θが１７度、１９度近辺のピーク面積（Ｓ_PL）が全体の面積に対して比較例２は１８％と５％よりも大きく、比較例３〜５は０％である。そのため結晶化した部分が十分にステレオコンプレックス構造物化してなかったり、していてもその比率が小さいことが分かる。
実施例７
実施例２で用いたＰＤＬＡ―２に代えてＰＤＬＡ―１を用い、また混練時間を３０分とする以外は、実施例２と同様に行い、ポリ乳酸系組成物及びポリ乳酸系ニ軸延伸フィルムを得た。
得られたポリ乳酸系組成物からなるプレスシート及びポリ乳酸ニ軸延伸フィルムを前記記載の方法で測定した。
測定結果を表３に示す。
実施例８
実施例２で用いたＰＤＬＡ―２に代えてＰＤＬＡ―１を用い、また混練時間を４０分とする以外は、実施例２と同様に行い、ポリ乳酸系組成物及びポリ乳酸系ニ軸延伸フィルムを得た。
得られたポリ乳酸系組成物からなるプレスシート及びポリ乳酸ニ軸延伸フィルムを前記記載の方法で測定した。
測定結果を表３に示す。
実施例９
混練時間を３０分とする以外は、実施例２と同様に行い、ポリ乳酸系組成物及びポリ乳酸系ニ軸延伸フィルムを得た。
得られたポリ乳酸系組成物からなるプレスシート及びポリ乳酸ニ軸延伸フィルムを前記記載の方法で測定した。
測定結果を表３に示す。

表３の実施例７〜９に示すように、本発明のポリ乳酸系延伸フィルムは混練時間が長く

なることで、更にＤＳＣ測定における１５０〜２００℃の範囲にある吸熱ピークの最大吸

熱ピーク（ピーク１）と２０５〜２４０℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク２）とのピーク比（ピーク１／ピーク２）が小さくなり、２４０℃の範囲にある吸熱ピークの吸熱量、降温時の発熱量が大きくなることが分かる。
また、かかる熱融解特性を有するポリ乳酸系延伸フィルムを得るには、ポリ乳酸系組成物の第１回降温時の発熱量も混練時間が長くなると大きく、第２回昇温時における１５０〜２００℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク１０）と２０５〜２４０℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク２０）とのピーク比（ピーク１０／ピーク２０）が小さくなることが分かる。
また実施例７、８、９のフィルムを並べて目から３０ｃｍの場所に位置し、８ｍ先にある蛍光灯の灯りを見たところ、混練時間が３０分の実施例７はやや蛍光灯の像の輪郭がぼやけているのに対して、混練時間が４０分の実施例８は蛍光灯の像の輪郭がはっきり見える。
またこの見え方は分子量が高いＰＤＬＡ２を用いた混練時間３０分の実施例９と同程度である。
このことから混練時間を長くすればフィルムの明澄性が向上するのは明らかである。
また分子量の高いＤＰＬＡを用いたフィルムの明澄性が向上するのも明らかである。
実施例１０
実施例１で得られた厚さ約３００μｍのポリ乳酸系組成物からなるシートを用いて前記のパンタグラフ式バッチ二軸延伸装置（ブルックナー社製）を用い行った。
予熱：７５℃×１分（ホットエアー）
延伸倍率：３×３
方法：同時２軸
延伸速度：２．１ｍ／分
緩和率：２．５％
ヒートセット：２００℃×１分
得られたニ軸延伸フィルムを前記記載の方法で測定した。測定結果を表４に示す。
実施例１１
延伸方法を逐次２軸の倍率３×３（ＭＤ→ＴＤ）とした以外は、実施例１０と同様に行い、ニ軸延伸フィルムを得た。
得られたニ軸延伸フィルムを前記記載の方法で測定した。測定結果を表４に示す。
実施例１２
延伸方法を同時２軸の倍率４×４とした以外は、実施例１０と同様に行い、ニ軸延伸フィルムを得た。
得られたニ軸延伸フィルムを前記記載の方法で測定した。測定結果を表４に示す。
実施例１３
延伸方法を逐次２軸の倍率４×４（ＭＤ→ＴＤ）とした以外は、実施例１０と同様に行い、ニ軸延伸フィルムを得た。
得られたニ軸延伸フィルムを前記記載の方法で測定した。測定結果を表４に示す。
実施例１４
延伸方法を２段逐次２軸の倍率３×４×１．３（ＭＤ→ＴＤ→ＭＤ）とした以外は、実施例１０と同様に行い、ニ軸延伸フィルムを得た。
得られたニ軸延伸フィルムを前記記載の方法で測定した。測定結果を表４に示す。

表４の実施例１０〜１４に示すように、本発明のポリ乳酸系延伸フィルムはいずれも、ＤＳＣ測定における１５０〜２００℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク１）と２０５〜２４０℃の範囲にある吸熱ピークの最大吸熱ピーク（ピーク２）とのピーク比（ピーク１／ピーク２）が０．０９〜０．１２といずれも０．２以下であり、２０５〜２４０℃の範囲にある吸熱ピークの吸熱量は５７．２〜６３．２Ｊ／ｇであり、ＳＣ構造の結晶が優先的に形成され耐熱性に優れることが分かる。
また実施例１０〜１４の中で比べると延伸倍率の高い実施例１２〜１４が実施例１０〜１２に比べて面配向度が大きく、フィルム剛性、破断強度が高い、またＭＤ方向のＴＭＡ伸度も１００〜１６０℃の実用的な使用範囲では変化率が実施例１０、１１に比べて小さかった。特に逐次２軸、２段階２軸で成形した実施例１３、１４は１００〜１６０℃の変化量が１％以下と耐熱性に優れていることが分かる。

As shown in Examples 2 to 6 in Table 2, all of the polylactic acid-based stretched films of the present invention are DS.

Peak ratio (peak 1 / peak 2) between the maximum endothermic peak (peak 1) in the range of 150 to 200 ° C. and the maximum endothermic peak (peak 2) in the range of 205 to 240 ° C. in C measurement ) Is 0.06 to 0.18 and both are 0.2 or less, and the endothermic peak in the range of 205 to 240 ° C. is 45.0 to 62.4 J / g and both are 40 J / g or more. In addition, the calorific value when the temperature is lowered is 46.1 to 71.4 J / g, which is 40 J / g or more, and it is understood that the heat resistance is excellent.
Moreover, in order to obtain the polylactic acid-type stretched film which has this heat melting characteristic, the calorific value at the time of the 1st temperature fall of a polylactic acid-type composition is large, and the endotherm in the range of 150-200 degreeC at the time of the 2nd temperature rise. A polylactic acid-based composition having a peak ratio (peak 10 / peak 20) between the maximum endothermic peak (peak 10) and the endothermic peak (peak 20) in the range of 205 to 240 ° C. of 0.5 or less. It can be seen that it is preferable to use.
In Examples 2 to 6, the peak areas (S _SC ) in the vicinity of 12 degrees, 21 degrees, and 24 degrees in the wide-angle X-ray measurement are 24 to 32%, 20% or more, and 2θ is 17%. The peak area (S _PL ) around 19 degrees is 0% and 5% or less with respect to the entire area.
Therefore, it can be seen that the crystallized portion has a stereo complex structure, and the ratio is large.
On the other hand, even if poly-L-lactic acid and poly-D-lactic acid having the same mixing ratio as in Examples 2, 4, 5, and 6 were used, the stretched films of Comparative Examples 2 to 5 were 150 to 200 ° C. in DSC measurement. The peak ratio (peak 1 / peak 2) of the maximum endothermic peak (peak 1) in the endothermic range to the maximum endothermic peak (peak 2) in the range from 205 to 240 ° C. is 0.73 to 1 .39 and 0.2 are over and it turns out that it is inferior to heat resistance.
Moreover, the maximum endothermic peak (peak 10) and 205-240 of the endothermic peak in the range of 150-200 degreeC in the time of the 2nd temperature rise of the kneaded material (press sheet) used as the raw material of the stretched film of Comparative Examples 2-4. The peak ratio (peak 10 / peak 20) of the endothermic peak in the range of ° C to the maximum endothermic peak (peak 20) is 1.50 to 4.00, which exceeds 0.5.
In Comparative Examples 2 to 5, the peak areas (S _SC ) around 12 degrees, 21 degrees, and 24 degrees in the wide-angle X-ray measurement are 5 to 19% and less than 20% with respect to the entire area, and 2θ is 17 In Comparative Example 2, the peak area (S _PL ) in the vicinity of 19 degrees and 19 degrees is 18% and larger than 5% with respect to the entire area, and Comparative Examples 3 to 5 are 0%. Therefore, it can be seen that the crystallized portion does not have a sufficient stereocomplex structure, or the ratio is small.
Example 7
A polylactic acid-based composition and a polylactic acid-based biaxially stretched film were obtained in the same manner as in Example 2 except that PDLA-1 was used instead of PDLA-2 used in Example 2, and the kneading time was 30 minutes. Got.
The press sheet and polylactic acid biaxially stretched film which consisted of the obtained polylactic acid-type composition were measured by the method of the said description.
Table 3 shows the measurement results.
Example 8
A polylactic acid composition and a polylactic acid biaxially stretched film were prepared in the same manner as in Example 2 except that PDLA-1 was used instead of PDLA-2 used in Example 2 and the kneading time was 40 minutes. Got.
The press sheet and polylactic acid biaxially stretched film which consisted of the obtained polylactic acid-type composition were measured by the method of the said description.
Table 3 shows the measurement results.
Example 9
A polylactic acid composition and a polylactic acid biaxially stretched film were obtained in the same manner as in Example 2 except that the kneading time was 30 minutes.
The press sheet and polylactic acid biaxially stretched film which consisted of the obtained polylactic acid-type composition were measured by the method of the said description.
Table 3 shows the measurement results.

As shown in Examples 7 to 9 in Table 3, the polylactic acid-based stretched film of the present invention has a long kneading time.

Thus, the maximum absorption of the endothermic peak in the range of 150 to 200 ° C. in DSC measurement.

The peak ratio (Peak 1 / Peak 2) between the thermal peak (Peak 1) and the maximum endothermic peak (Peak 2) of the endothermic peak in the range of 205-240 ° C is reduced, and the endothermic peak in the range of 240 ° C is absorbed. It can be seen that the amount of heat and the amount of heat generated when the temperature falls are large.
Moreover, in order to obtain the polylactic acid-type stretched film which has this heat melting characteristic, the calorific value at the time of the 1st temperature fall of a polylactic acid-type composition will become large when kneading | mixing time becomes long, 150-200 degreeC in the time of the 2nd temperature rise. It can be seen that the peak ratio (peak 10 / peak 20) between the maximum endothermic peak (peak 10) in the endothermic peak range and the maximum endothermic peak (peak 20) in the endothermic peak range (205 to 240 ° C.) is small. .
Further, when the films of Examples 7, 8, and 9 were placed side by side and located at a position 30 cm from the eyes and the lamp of a fluorescent lamp 8 m ahead was viewed, Example 7 was slightly mixed with a fluorescent lamp image of 30 minutes. In contrast to the blurred outline, in Example 8 where the kneading time is 40 minutes, the outline of the fluorescent lamp image is clearly visible.
This appearance is similar to that in Example 9 in which the kneading time is 30 minutes using PDLA2 having a high molecular weight.
From this, it is clear that the clarity of the film is improved if the kneading time is increased.
It is also clear that the clarity of the film using DPLA having a high molecular weight is improved.
Example 10
Using the sheet made of the polylactic acid composition having a thickness of about 300 μm obtained in Example 1, the pantograph batch biaxial stretching apparatus (manufactured by Bruckner) was used.
Preheating: 75 ° C x 1 minute (hot air)
Stretch ratio: 3 × 3
Method: Simultaneous biaxial stretching speed: 2.1 m / min Relaxation rate: 2.5%
Heat set: 200 ° C. × 1 minute The obtained biaxially stretched film was measured by the method described above. Table 4 shows the measurement results.
Example 11
A biaxially stretched film was obtained in the same manner as in Example 10 except that the stretching method was sequentially changed to a biaxial magnification of 3 × 3 (MD → TD).
The obtained biaxially stretched film was measured by the method described above. Table 4 shows the measurement results.
Example 12
A biaxially stretched film was obtained in the same manner as in Example 10 except that the stretching method was simultaneously biaxial magnification 4 × 4.
The obtained biaxially stretched film was measured by the method described above. Table 4 shows the measurement results.
Example 13
A biaxially stretched film was obtained in the same manner as in Example 10 except that the stretching method was successively changed to biaxial magnification 4 × 4 (MD → TD).
The obtained biaxially stretched film was measured by the method described above. Table 4 shows the measurement results.
Example 14
A biaxially stretched film was obtained in the same manner as in Example 10 except that the stretching method was changed to a two-stage sequential biaxial magnification of 3 × 4 × 1.3 (MD → TD → MD).
The obtained biaxially stretched film was measured by the method described above. Table 4 shows the measurement results.

As shown in Examples 10 to 14 of Table 4, all of the polylactic acid-based stretched films of the present invention have a maximum endothermic peak (peak 1) and 205 to 240 of the endothermic peak in the range of 150 to 200 ° C. in DSC measurement. The peak ratio (peak 1 / peak 2) of the endothermic peak in the range of ° C to the maximum endothermic peak (peak 2) is 0.09 to 0.12, both being 0.2 or less, and the range of 205 to 240 ° C. The endothermic amount of the endothermic peak is 57.2 to 63.2 J / g, and it can be seen that crystals having an SC structure are formed preferentially and have excellent heat resistance.
Moreover, compared with Examples 10-14, Examples 12-14, which have a higher draw ratio, have a higher degree of plane orientation, higher film rigidity and breaking strength than Examples 10-12, and TMA elongation in the MD direction. In the practical use range of 100 to 160 ° C., the rate of change was smaller than those in Examples 10 and 11. In particular, Examples 13 and 14 formed by sequential biaxial and two-stage biaxial are excellent in heat resistance with a change amount of 100 to 160 ° C. being 1% or less.

The composition of the present invention has specific thermal properties. This is presumably because the stereocomplex structure is easily and selectively formed.
For this reason, the stretched film is superior in heat resistance and toughness as compared to a molded product such as a conventional polylactic acid-based stretched film, and is further excellent in surface smoothness, transparency, and thermal stability.

  This is because a stereocomplex structure is selectively formed upon crystallization from an amorphous state, and the crystallization treatment is easy with the composition of the present invention.

Claims (11)

  Poly-L-lactic acid and poly-D-lactic acid, 75 to 25 parts by weight of the poly-L-lactic acid, and 25 to 75 parts by weight of the poly-D-lactic acid (poly-L-lactic acid and The poly-D-lactic acid is a polylactic acid composition obtained by melt-kneading and heat-treating after stretching, and having a ΔHc of 20 J / g or more in the DSC measurement. Of the endothermic peak in the range of 150 ° C. to 200 ° C. (peak 1) and the maximum endothermic peak height of the endothermic peak in the range of 205 ° C. to 240 ° C. (peak 2). A polylactic acid-based stretched film having a peak ratio (peak 1 / peak 2) of 0.2 or less and a degree of plane orientation of 0.006 or more.   The stretched polylactic acid film according to claim 1, wherein the heat treatment temperature is 140 ° C to 200 ° C, and the heat treatment time is 1 second or longer.   The stretched polylactic acid film according to claim 1, wherein the heat treatment temperature is 150 ° C to 200 ° C, and the heat treatment time is 3 seconds to 60 seconds.   The polylactic acid-based stretched film according to any one of claims 1 to 3, wherein the endothermic amount of the endothermic peak in the range of 205 ° C to 240 ° C is 40 J / g or more.   The polylactic acid-based stretched film according to any one of claims 1 to 4, wherein after the endothermic peak measurement in the DSC measurement, the calorific value when the temperature is lowered is 40 J / g or more.   The sum of peak areas (SSC) in the vicinity of 12 °, 21 °, and 24 ° in wide-angle X-ray measurement is 20% or more of the entire area, and 2θ is the peak area in the vicinity of 17 ° and 19 °. The polylactic acid-based stretched film according to any one of claims 1 to 5, wherein the total sum (SPL) is 5% or less with respect to the entire area.   The polylactic acid-based stretching according to any one of claims 1 to 6, wherein in the DSC measurement, a polylactic acid-based composition having a calorific value of 20 J / g or more when stretched at 250 ° C for 10 minutes has been stretched. the film.   In the DSC measurement, the peak endothermic peak height (peak 10) in the range of 150 ° C. to 200 ° C. at the second temperature increase and the peak endothermic peak in the range of 205 ° C. to 240 ° C. The polylactic acid-based composition according to any one of claims 1 to 6, wherein a polylactic acid-based composition having a peak ratio (peak 10 / peak 20) to a peak height (peak 20) of 0.5 or less is stretched. Stretched film.   7. The polylactic acid composition obtained by stretching a polylactic acid-based composition having an endothermic amount of 35 J / g or more in the range of 205 ° C. to 240 ° C. in the second temperature increase in DSC measurement. 2. A polylactic acid-based stretched film described in 1.   The stretched polylactic acid film according to any one of claims 1 to 9, wherein the stretched film is stretched at least twice in one direction.   The stretched polylactic acid film according to any one of claims 1 to 9, which is stretched twice or more in the longitudinal direction and twice or more in the transverse direction.

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