JPH08198955A - Oriented polylactic acid film and sheet and their production - Google Patents

Abstract

PURPOSE: To provide an oriented polylactic acid film or sheet having strength and dimensional stability sufficient for ordinary use and provide a process for the production of the film or sheet. CONSTITUTION: This oriented polylactic acid film or sheet has a planar orientation degree ΔP of >=3.0×10<-3> and satisfies the formulas (ΔHm-ΔHc)>=20J/g and (ΔHm-ΔHc)/ΔHm>=0.75 wherein ΔHm is heat of crystal fusion generated by raising the temperature of the film or sheet and ΔHc is heat of crystallization generated by the crystallization during temperature increase. The film or sheet is produced by heat-treating a film or sheet of a polylactic acid polymer having a planar orientation degree ΔP of >=3.0×10<-3> under conditions to satisfy (1) the heat-treatment temperature T( deg.C) is between 70 deg.C and the melting point Tm of the polymer and (2) the heat-treatment period t(sec) satisfies the formula Log(t)>=-4.6Log(T)+11. The shrinkage of the film or sheet at 80 deg.C is <=3%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film and sheet made of a polylactic acid polymer and a method for producing them.

[0002]

2. Description of the Related Art At present, polyethylene terephthalate stretched film, polypropylene stretched film and the like are known as materials having excellent transparency and high mechanical strength.
While this film can be given dimensional stability by heat treatment due to its crystallinity, it is also used as a shrink film by reducing the crystallinity by copolymerization or by selecting stretching / heat treatment conditions. . The proportion of these films used in the packaging field is also high. However, since these plastic films are chemically and biologically stable, they do not decompose when scattered in the natural environment and pollute the living environment of birds and animals. Further, even if the waste is collected and landfilled, it remains without being decomposed and shortens the life of the landfill.

Therefore, there is a demand for a material composed of a decomposable polymer that does not cause these problems.
Development is being done. One example is polylactic acid. It is known that polylactic acid undergoes spontaneous hydrolysis in soil or water, does not remain in its original form in soil or water, and then becomes a harmless decomposed product by microorganisms.

However, a film or sheet made of polylactic acid is a fragile material having low elongation as it is. By stretching and orienting the polylactic acid polymer, the strength and elongation is improved,
It is known that the brittleness is improved, but as it is, the dimensional stability is poor in an atmosphere above the glass transition point, and the range of use must be limited depending on the application.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an oriented polylactic acid-based film or sheet having strength and dimensional stability that do not hinder normal use and a method for producing the same.

[0006]

Means for Solving the Problems For the above-mentioned purpose, the present inventors have made earnest studies and, as a result, have made a film or sheet comprising a polylactic acid-based polymer and having a plane orientation degree ΔP of 3.0 × 10 ⁻³ or more. The difference (ΔHm-ΔHc) between the heat of crystal fusion ΔHm when the film / sheet is heated and the heat of crystallization ΔHc generated by crystallization during heating is 20 J.
/ G or more and (ΔHm-ΔHc) / ΔHm is 0.7
If it is 5 or more, the shrinkage at 80 ° C is at most 3%
I found it within.

Further, for the above-mentioned purpose, the present inventor has made earnest studies and, as a result, made up of a polylactic acid-based polymer and had a plane orientation degree ΔP.
Of a molded product such as a film or sheet having a heat treatment temperature of 3.0 × 10 ⁻³ or more, a heat treatment temperature T (° C.) within a range of 70 ° C. to (melting point Tm of polymer), and a heat treatment temperature t (second) Logt
The present invention has been completed by discovering that the shrinkage rate at 80 ° C. is within 3% by heat treatment under the condition of satisfying ≧ −4.6 LogT + 11.

That is, the oriented polylactic acid-based film or sheet according to the first solution of the present invention has a plane orientation degree ΔP of 3.0 × 10 ⁻³ or more, and the heat of crystal fusion when the film or sheet is heated. Difference between ΔHm and heat of crystallization ΔHc generated by crystallization during heating (ΔHm-ΔHc)
Is 20 J / g or more, and (ΔHm-ΔHc) / ΔHm
Is 0.75 or more.

The oriented polylactic acid-based film or sheet according to the second solution of the present invention is the film or sheet according to the above-mentioned first solution, wherein the lactic acid is L-lactic acid or D-lactic acid, or a mixture thereof. , The ratio is within the range of 100: 0 to 94: 6 or 0: 100.
It is characterized by comprising a copolymer or a mixture thereof within the range of to 6:94.

A method for producing an oriented polylactic acid-based film or sheet according to the third solution of the present invention is a method for producing a polylactic acid-based polymer film or sheet having a degree of plane orientation ΔP of 3.0 × 10 ⁻³ or more at a heat treatment temperature. T (° C) is 70 ° C to (melting point T of polymer
m), heat treatment time t (seconds) is Logt ≧ −4.6LogT
It is characterized in that the heat treatment is performed under the condition that +11 is satisfied.

The method for producing an oriented polylactic acid-based film or sheet according to the fourth solution of the present invention is the method according to the third solution, wherein lactic acid is L-lactic acid or D-lactic acid.
Lactic acid, or a mixture thereof, with a ratio of 10
Within the range of 0: 0 to 94: 6 or 0: 100 to 6:94
It is characterized by comprising a copolymer within the range of or a mixture thereof.

The present invention will be described in detail below.

The polylactic acid-based polymer used in the production of the film / sheet in the present invention is polylactic acid or a copolymer of lactic acid and another hydroxycarboxylic acid, or a mixture thereof, and the effect of the present invention is obtained. Other polymer materials may be mixed in such a range that does not hinder it. In addition, molding processability,
For the purpose of adjusting the physical properties of the film, it is possible to add additives such as a plasticizer, a lubricant, an inorganic filler and an ultraviolet absorber, and a modifier.

Examples of lactic acid include L-lactic acid and D-lactic acid. Other hydroxycarboxylic acids include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid and 3-hydroxybutyric acid.
Representative examples thereof include hydroxyvaleric acid, 4-hydroxyvaleric acid, and 6-hydroxycaproic acid.

As the polymerization method, any known method such as condensation polymerization method and ring-opening polymerization method can be adopted, and a small amount of a chain extender such as diisocyanate is used for the purpose of increasing the molecular weight. A compound, an epoxy compound, an acid anhydride, etc. may be used. The weight average molecular weight of the polymer is preferably 50,000 to 1,000,000, and practical physical properties are hardly expressed below this range.
If it exceeds, the melt viscosity becomes too high and the moldability becomes poor.

The polylactic acid-based film / sheet in the present invention is obtained by melting these polymers by a general melt-molding method such as an extrusion method, a calender method, a pressing method or the like to obtain a flat or cylindrical unstretched sheet or a sheet-shaped melt. Body and then
This can be obtained by stretching by a roll method, a tenter method, a tubular method, an inflation method or the like.

Film forming conditions for the unstretched film / sheet will be described. The polylactic acid polymer is sufficiently dried to remove water, and then melted by an extruder. Since the melting temperature changes depending on the composition, it is preferable to appropriately select the melting temperature. In practice, a temperature range of 140 ° C to 250 ° C is usually chosen. The melted polylactic acid polymer is formed into a film or sheet. The thickness of the sheet is usually 5 μm
It is 500 μm.

The polymer melt-formed into a film or sheet is preferably brought into contact with a rotating casting drum (cooling drum) to be rapidly cooled. The temperature of the casting drum is suitably 60 ° C. or lower. If it is higher than this, the polymer sticks to the casting drum and cannot be removed.Also, crystallization is promoted, and spherulites develop and it becomes impossible to stretch.Therefore, it is set to the above temperature range and rapidly cooled to become substantially amorphous. Preferably.

The stretching method may be uniaxial stretching, sequential biaxial stretching or simultaneous biaxial stretching. In the above-described stretching of the unstretched sheet / film, the stretching ratio is appropriately selected in the range of 1.5 to 5 times in the longitudinal direction and the transverse direction, and the stretching temperature is appropriately selected in the range of 50 ° C to 90 ° C. In the present invention, it is important to increase the plane orientation degree ΔP, which is 1.0 × 10 ⁻³ or less in the unstretched non-oriented sheet / film, to 3.0 × 10 ⁻³ or more. Hereinafter, the characteristics of the film / sheet will be described taking the film as an example, but the same applies to the case of the sheet.

In the present invention, the degree of plane orientation ΔP of the film is determined by the balance between the composition of the polymer and the molding processing conditions.
And the difference between the heat of crystal fusion and the heat of crystallization of the film (ΔH
m-ΔHc) and (ΔHm-ΔHc) / ΔHm,
It is most important that each be a certain value or more.

That is, in the polylactic acid-based film, the inherent brittleness of the material is improved by increasing ΔP, and the thermal dimensional stability that decreases with an increase in ΔP is defined as (ΔHm-ΔHc). (ΔHm-ΔHc) /
It can be improved by increasing ΔHm and ΔHm, respectively.

ΔP represents the degree of orientation in the plane direction with respect to the thickness direction of the film, and is usually calculated by the following formula by measuring the bending ratio in the directions of three orthogonal axes.

[0023]

## EQU1 ## ΔP = {(γ + β) / 2} -α (α <β <γ) where γ and β are biaxial refractive indices parallel to the film surface, and α is a refractive index in the film thickness direction. Is.

ΔP depends on the crystallinity and crystal orientation, but largely depends on the molecular orientation in the film plane. That is, the increase in ΔP leads to an increase in the molecular orientation in the plane of the film, particularly in the flow direction of the film and / or a direction orthogonal thereto, thereby increasing the strength of the film and improving the brittleness.

As a method for increasing ΔP, a molecular orientation method using an electric field or a magnetic field can be adopted in addition to any known film stretching method.

However, if ΔP is 3.0 × 10 ⁻³ or more, the thermal dimensional stability of the film becomes poor, and the film shrinks during the hot summer months, making it unusable as a film. Therefore, it is important whether or not the original shape can be obtained without shrinking in an atmosphere of slightly higher than room temperature and 50 ° C. or higher, and preferably dimensional stability at 80 ° C. or higher (for example, shrinkage ratio within 3%). If there is, it can sufficiently withstand normal use.

In the case of a polylactic acid-based film having a ΔP of 3.0 × 10 ⁻³ or more, the (ΔHm-ΔHc) of the film is 20 J / g or more in order to obtain practical thermal dimensional stability.
In addition, it is important to control (ΔHm-ΔHc) / ΔHm to 0.75 or more. By satisfying this condition, 80
The shrinkage rate at ° C can be suppressed within 3%.

ΔHm and ΔHc are the heat of fusion of crystal and the heat of crystallization, respectively, and are determined by differential scanning calorimetry (DSC) of a film sample. That is, ΔHm
Is the amount of heat required to dissolve all the crystals when the temperature is raised at a heating rate of 10 ° C./minute, and is calculated from the area of the endothermic peak due to crystal melting that appears near the crystal melting point of the polymer. Further, ΔHc is obtained from the area of the exothermic peak generated during crystallization that occurs during the temperature rising process.

ΔHm mainly depends on the crystallinity of the polymer itself, and takes a large value for a polymer having high crystallinity. By the way, the complete homopolymer of L-lactic acid or D-lactic acid is 60 J / g or more, and in the copolymer of these two types of lactic acid, ΔHm changes depending on the composition ratio. ΔHc is an index relating to the crystallinity of the film at that time with respect to the crystallinity of the polymer, and when ΔHc is large, the crystallization of the film is progressing in the temperature rising process. That is, it means that the crystallinity of the film was relatively low based on the crystallinity of the polymer. On the contrary, when ΔHc is small, it means that the crystallinity of the film was relatively high based on the crystallinity of the polymer.

From the aspect of the manufacturing method of the film / sheet, the heat treatment to impart the dimensional stability is to increase the crystallinity of the film / sheet (hereinafter, simply referred to as “film”).

That is, one direction for increasing (ΔHm-ΔHc) is to form a film having a relatively high degree of crystallinity from a polymer having a high crystallinity as a raw material. The crystallinity of the film depends to a large extent on the composition of the polymer and it is necessary to select a polymer with a relatively high degree of crystallinity.
Polylactic acid has a structural unit composed of L-lactic acid and a structural unit composed of D-lactic acid, and is composed of either a simple substance (homopolymer) or a mixture (copolymer) or a mixture thereof. In some cases, the crystallinity may be lost due to the difference in crystallinity depending on the composition ratio of the L-lactic acid structural unit and the D-lactic acid structural unit. An amorphous polymer or a polymer having crystallinity but low crystallinity cannot impart dimensional stability by heat treatment, and depending on the conditions, the imparted orientation may be relaxed and the strength may be greatly reduced.

In order to increase the crystallinity of the polymer, it is necessary that ΔHm of the polymer itself is 20 J / g or more. In this case, the composition ratio of L-lactic acid and D-lactic acid is 10
Within the range of 0: 0 to 94: 6 or 0: 100 to 6:94
It is preferably within the range of. That is, if the mixing ratio of L-lactic acid or D-lactic acid exceeds 6%, the crystallinity is too low, so the mixing ratio is preferably 6% or less.

Further, in order to reduce ΔHc, that is, in order to increase the crystallinity of the film, it is important to select the film processing conditions.

Further, (ΔHm-ΔHc) / ΔHm is 0.
It is important that it is 75 or more. If this value is less than 0.75, the shrinkage ratio at 80 ° C., which is a practical index of thermal dimensional stability, cannot be suppressed to within 3%.

The film forming conditions are as follows: polylactic acid film having ΔP of 3.0 × 10 ⁻³ or more.
In order to obtain practical thermal dimensional stability, it is important to perform heat treatment at a film crystallization temperature or higher. However, the higher the degree of orientation of the film, the lower the crystallization temperature tends to be, and the heat treatment temperature can be appropriately selected depending on the degree of orientation. The effect can be obtained if the heat treatment is performed at least at 70 ° C. or higher. However, if the heat treatment time is short, the effect of imparting dimensional stability is low. That is, if the heat treatment time is short, the shrinkage rate at 80 ° C. or higher cannot be suppressed. It is necessary to select the heat treatment temperature and heat treatment time in consideration of the correlation between the two.

In order to increase the thermal dimensional stability of the film in the molding process step, particularly in the biaxial stretching by the tenter method, it is useful to increase the stretching ratio to promote oriented crystallization, and then heat-treat in an atmosphere having a crystallization temperature or higher. Is.

In the case of polylactic acid, the crystallization temperature tends to decrease as ΔP increases, and as a result of intensive studies, heat treatment was carried out at a heat treatment temperature T (° C) in the range of 70 ° C to (melting point Tm of polymer). Time t (seconds) is Logt ≧ −4.6Lo
80 by heat treatment under the condition that gT + 11 is satisfied
It was found that the heat shrinkage rate at 0 ° C can be suppressed to 3% or less.

For example, thermal dimensional stability can be imparted by heat-treating at least 70 ° C. or higher, more preferably 90 to 170 ° C. for 3 seconds or longer. Within this range, the higher the heat treatment temperature and the longer the heat treatment time, the better the thermal dimensional stability.

[0039]

EXAMPLES Examples will be shown below, but the present invention is not limited thereto. The measured values shown in the examples were measured and calculated under the following conditions.

(1) ΔP The refractive index (α, β,
γ) was measured and calculated by the following formula.

[0041]

## EQU2 ## ΔP = {(γ + β) / 2} -α (α
<Β <γ) γ: Maximum refractive index in the film plane β: Refractive index in the film in-plane direction orthogonal thereto α: Refractive index in the film thickness direction (2) ΔHm-ΔHc Using Perkin Elmer DSC-7, Based on JIS-K7122, a heat quantity of crystal fusion ΔHm and a heat quantity of crystallization ΔHc of crystal fusion were calculated from thermograms when the temperature of the film sample was raised at a temperature rising rate of 10 ° C./min.

(3) Tensile strength Tensile strength of Toyo Seiki Tensilon II machine was used for the tensile strength according to JIS.
-Measured based on K7127. Tensile strength is 100
mm / min. MD indicates the flow direction of the film, and TD indicates the direction orthogonal to the flow of the film.

(4) Shrinkage rate The film sample is 100 mm × 1 along MD and TD.
After cutting it out to 00 mm and immersing it in a hot water bath at 80 ° C. for 5 minutes, the vertical and horizontal dimensions were measured, and each shrinkage rate was calculated according to the following formula.

[0044]

(Equation 3)

Experimental Example 1 Polylactic acid having a glass transition temperature of 58 ° C. and a weight average molecular weight of 180,000 was used in a 30 mmφ uniaxial extension with the ratio of the structural unit consisting of L-lactic acid and the structural unit consisting of D-lactic acid being approximately 98: 2. In the ruder, T at 200 ℃
It was extruded from a die and quenched with a casting roll to obtain an unstretched sheet having a thickness of 250 μm. The plane orientation degree ΔP of this sheet is 0.1 × 10 ⁻³ , and the tensile strengths in the longitudinal direction and its width direction are 720 kgf / cm ² and 700 k, respectively.
It was gf / cm ² .

Subsequently, roll stretching was carried out in the longitudinal direction so that the degree of plane orientation ΔP was 3 × 10 ⁻³ or more, then stretching was carried out with a tenter in the width direction, and heat treatment was carried out in the tenter. The stretching conditions and the subsequent heat treatment conditions were variously changed to obtain N shown in Table 1.
o. The film samples of Nos. 1 to 7 and No. 1 shown in Table 2.
8-9 film samples were obtained. The flow rate of the film is 2 m / min, and the passing time through each stretching / heat treatment zone is about 30 seconds.

Next, polylactic acid having a ratio of structural units of L-lactic acid and structural units of D-lactic acid of about 96: 4, a glass transition point of 57 ° C. and a weight average molecular weight of 140,000 is extruded by the same method as described above. Then, stretching and heat treatment are performed, and Table 2
No. shown in. 10 and 11 films were obtained. The degree of plane orientation ΔP of the sheet before stretching and heat treatment is 0.1 × 10 ⁻³
Hereinafter, the tensile strengths in the longitudinal direction and the width direction were 650 kgf / cm ² and 660 kgf / cm ² , respectively.

By the same method, the ratio of the structural unit composed of L-lactic acid to the structural unit composed of D-lactic acid was approximately 93: 7.
Polylactic acid having a glass transition temperature of 55 ° C. and a weight average molecular weight of 110,000 was extruded, followed by stretching and heat treatment.
o. 12 films were obtained. No. 2 in Table 2 When heat treatment was performed at 140 ° C. as shown in 13, melt flow occurred. The degree of plane orientation ΔP of the sheet before stretching and heat treatment is 0.1 ×
The tensile strength was 10 ⁻³ or less, and the tensile strength in each of the longitudinal direction and the width direction was 610 kgf / cm ² .

[0049]

[Table 1]

[0050]

[Table 2]

As is clear from the results of Tables 1 and 2, the plane orientation degree ΔP of the film is 3 × 10 by stretching.
^It can be seen that the strength becomes ^-3 or more and the strength is improved as compared with the non-stretched sheet. However, the heat treatment condition is outside the range of the present invention. 1, 3, 4 and 8 have high shrinkage rates.
In addition, No. No. 7 melted because it was heat-treated at a temperature higher than the melting point of the polymer. On the other hand, the heat treatment conditions within the range of the present invention No. 2, 5, 6 and 9 have excellent thermal dimensional stability.

Nos. L-lactic acid and D-lactic acid within the range of the present invention were used. No. 11 of the same composition also has excellent dimensional stability. 10 is (ΔHm-ΔH
c) is 20 J / g or more, but (ΔHm-ΔHc) /
It can be seen that ΔHm is outside the range of the present invention, and the heat shrinkage rate is high.

No. No. 12 has L-lactic acid and D-lactic acid outside the scope of the present invention, and the crystallinity of the polymer itself is low,
It can be seen that the thermal contraction rate is high even if (ΔHm−ΔHc) / ΔHm is 0.75 or more.

(Experimental Example 2) The ratio of the structural unit composed of L-lactic acid to the structural unit composed of D-lactic acid was approximately 98: 2, the glass transition point was 58 ° C., the melting point was 175 ° C., and the weight average molecular weight was 1
80,000 polylactic acid was extruded from a T-die at 200 ° C. in a 30 mmφ uniaxial extruder and rapidly cooled by a casting roll to obtain an unstretched sheet having a thickness of 250 μm.
The degree of plane orientation ΔP of this sheet is 0.1 × 10 ⁻³ or less, and the tensile strength in the longitudinal direction and its width direction is 720 kg.
f / cm ² and 700 kgf / cm ² .

Subsequently, roll stretching was carried out in the longitudinal direction so that the plane orientation degree ΔP became 3 × 10 ⁻³ or more, and then stretching was carried out in the width direction with a tenter, and heat treatment was carried out in the tenter. The stretching conditions and the subsequent heat treatment conditions were variously changed, and the No. 14 to 20 film samples and Nos. 21 film samples were obtained. The film flow speed is 1 to 20 m / min, the passage time in the heat treatment zone is 3
~ 60 seconds. However, No. shown in Table 4 For No. 21, after stretching, the film was heat treated as it was at 60 ° C. for 10 seconds in a tenter, the film was sandwiched between fixed frames, and heat treated in a hot air circulator kept at 80 ° C. atmosphere.

Polylactic acid having a ratio of structural units of L-lactic acid to structural units of D-lactic acid of about 96: 4, a glass transition point of 57 ° C., a melting point of about 152 ° C. and a weight average molecular weight of 140,000 is as described above. Extrusion was carried out in the same manner to prepare an unstretched film. Subsequently, stretching and heat treatment are performed, and No. 22 and 23 films were obtained. The degree of plane orientation ΔP of the sheet before stretching and heat treatment is 0.1 × 10 ⁻³ or less,
Tensile strength in the longitudinal direction and its width direction is 650
kgf / cm ^2, it was 660kgf / cm ^2.

In the same manner, the ratio of the structural unit composed of L-lactic acid to the structural unit composed of D-lactic acid was approximately 93: 7.
Then, polylactic acid having a glass transition point of 57 ° C. and a melting point of about 125 ° C. and a weight average molecular weight of 110,000 was extruded in the same manner as above to prepare an unstretched film. Then, stretching and heat treatment are performed.
No. shown in Table 4 Films of 24 and 25 were obtained. However, No. 25 is 70 in the tenter as it is after stretching
The film which was heat-treated at ℃ for about 13 seconds was sampled, the film was sandwiched in a fixed frame, and heat-treated in a hot air circulator kept at 80 ℃ atmosphere. The plane orientation degree ΔP of the sheet before stretching and heat treatment is 0.1 × 10 ⁻³ or less, and the tensile strengths in the longitudinal direction and its width direction are 610 kgf / cm ² and 610, respectively.
It was kgf / cm ² .

No. 1 shown in Table 3 was used. The relationship between the heat treatment time and the temperature of the film samples 14 to 20 is shown in FIG. The shaded area is the scope of the present invention, and No. 15, 1
7, 19 and 20 are examples of the present invention, and others are comparative examples.

[0059]

[Table 3]

[0060]

[Table 4]

As is clear from the results shown in Tables 3 and 4, the plane orientation degree ΔP of the film was 3 × 10 by stretching.
^It can be seen that the strength becomes ^-3 or more and the strength is improved as compared with the non-stretched sheet. However, the heat treatment conditions are outside the scope of the present invention. 14, 16 and 18 have relatively high shrinkage. On the other hand, the heat treatment conditions within the range of the present invention No.
15, 17 and 19-21 have excellent thermal dimensional stability.

Nos. L-lactic acid and D-lactic acid in which the ratio is within the range of the present invention. No. 23, which has the same composition, also exhibits excellent dimensional stability. No. 22 has a relatively high shrinkage rate because the heat treatment time is outside the range of the present invention.

No. It is understood that the heat treatment temperatures and times of 24 and 25 are within the range of the present invention, but the ratio of L-lactic acid and D-lactic acid is outside the range of the present invention, and the thermal dimensional stability is insufficient.

Although all of the above examples show the case where the ratio of L-lactic acid is high, the same result is obtained when the ratio of D-lactic acid is high.

[0065]

As a result of the present invention, a polylactic acid-based polymer having decomposability can be stretched and heat-treated to obtain a film or sheet excellent in practical strength and thermal dimensional stability.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between heat treatment time and temperature, which are the results of Table 3.

[Explanation of symbols]

 T heat treatment temperature (° C) t heat treatment time (seconds)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area C08L 67:04

Claims (4)

[Claims] 1. The degree of plane orientation ΔP is 3.0 × 10 ⁻³ or more, the heat of crystal fusion ΔHm when the film or sheet is heated, and the heat of crystallization Δ generated by crystallization during temperature increase.
An oriented polylactic acid-based film or sheet characterized by having a difference from Hc (ΔHm-ΔHc) of 20 J / g or more and (ΔHm-ΔHc) / ΔHm of 0.75 or more. 2. The lactic acid is L-lactic acid or D-lactic acid, or a mixture thereof, and the ratio thereof is 100: 0-9.
The oriented polylactic acid-based film or sheet according to claim 1, which is composed of a copolymer within the range of 4: 6 or within the range of 0: 100 to 6:94 or a mixture thereof. 3. A polylactic acid-based polymer film or sheet having a degree of plane orientation ΔP of 3.0 × 10 ⁻³ or more has a heat treatment temperature T (° C.) of 70 ° C. to (melting point T of polymer).
m), heat treatment time t (seconds) is Logt ≧ −4.6LogT
The method for producing an oriented polylactic acid-based film or sheet according to claim 1, wherein the heat treatment is performed under the condition that +11 is satisfied. 4. The lactic acid is L-lactic acid or D-lactic acid, or a mixture thereof, and the ratio thereof is 100: 0-9.
4. The method for producing an oriented polylactic acid-based film or sheet according to claim 3, which comprises a copolymer in the range of 4: 6 or in the range of 0: 100 to 6:94 or a mixture thereof.