JP2000302889A - Heat-shrinkable film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a film excellent in heat shrinkage characteristics and adhesion to a container and capable of being released by an alkaline aqueous solution by imparting a stretched film of a polymer composed mainly of a particle-containing polylactic acid with a heat shrinkage factor of a specific value or more and a maximum heat shrinkage stress of a specific value or less in hot air of a specific temperature. SOLUTION: There is provided a heat-shrinkable film having a thickness of 1-300 μm comprising a polymer composed mainly of a polylactic acid containing 0.01-1 wt.% of particles having an average particle size of 0.001-10 μm. The film has a heat shrinkage factor in at least one direction of at least 20% and a maximum heat shrinkage stress of 5.0 MPa or less in hot air of 120 deg.C and at least 50% of the film can be dissolved in an alkaline aqueous solution having a pH of at least 7. As the lactic acid polymer can be mentioned D-lactic acid polymers, L-lactic acid polymers, D-lactic acid/L-lactic acid copolymers, D-lactic acid/hydroxy carboxylic acid copolymers, and the like. As the particles are employed inorganic particles such as kaolin or the like, organic particles such as calcium oxalate or the like, crosslinked polymer particles such as styrene-divinylbenzene copolymers or the like, inner particles formed in a polymer, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention not only has solubility in an aqueous alkali solution and has excellent heat shrinkage properties,
The present invention relates to a heat-shrinkable film having excellent mechanical properties and heat resistance and used for shrink labels and food packaging.

[0002]

2. Description of the Related Art Conventionally, heat shrinkable films have been used as shrink labels for bottles, polyethylene terephthalate (hereinafter abbreviated as PET) bottles and the like.

[0003] In particular, as a shrink label for food packaging, a stretched film composed of, for example, an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, polyvinyl chloride, and polystyrene, which has a large shrinkage ratio due to heat, is mainly used. Has been used.

[0004]

However, in recent years, there has been a demand for a polyester-based heat-shrinkable film having excellent safety and hygiene properties, chemical resistance, and transparency. For example, neopentyl glycol or isophthalic acid is used for PET. A stretched film comprising a copolymerized polyester has been proposed (JP-A-63-156833, JP-A-63-2024).
No. 29, JP-B-63-7573).

[0005] However, these films cannot be said to have sufficiently reduced the heat shrinkage stress, and there has been a problem that some containers may be deformed, and if they are shrunk without deformation of the container, the heat shrinkage rate may be insufficient.

In recent years, it has been demanded to collect bottles and PET bottles. In order to collect those containers, it is necessary to remove the heat-shrinkable film attached to those containers. In the case of a label using a water-soluble paste, the label can be removed from the container by dipping in an aqueous solution, but in the case of a heat-shrinkable film, since the label is adhered to the container by heat shrinkage, It cannot be removed from the container by immersion. There is a problem that the heat-shrinkable film must be removed from each container in order to collect the containers.

Accordingly, it is an object of the present invention to provide a heat-shrinkable film which is excellent in heat shrinkage characteristics and container adhesion and which can be dissolved in an alkaline aqueous solution and peeled off from the container.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
A stretched film comprising a polymer mainly composed of polylactic acid containing 0.01 to 1% by weight of particles,
Heat shrinkage in at least one direction in hot air of 20 ° C. is 20
% Or more, and the maximum heat shrinkage stress of the film is 5.0MP.
This is achieved by a heat-shrinkable film characterized by being equal to or less than a.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described.

[0010] The particles used in the heat shrinkable film of the present invention are:
It is necessary to contain 0.01 to 1% by weight in a polymer mainly composed of polylactic acid. More preferably 0.01 to
0.5% by weight. The particles to be contained are not particularly limited as long as they are inert to the polylactic acid polymer,
As the particles, inorganic particles, organic particles, crosslinked polymer particles,
Internal particles generated in the polymerization system can be exemplified. Two or more of these particles may be contained.

The inorganic particles are not particularly limited.
Examples include calcium carbonate, kaolin, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, and lithium fluoride. Examples of the organic particles include calcium oxalate and terephthalates such as calcium, barium, zinc, manganese, and magnesium.

Examples of the crosslinked polymer particles include homopolymers or copolymers of vinyl monomers such as divinylbenzene, styrene, acrylic acid, and methacrylic acid. In addition, organic fine particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, and thermosetting phenol resin are also preferably used. As the internal particles produced in the polymerization system, those produced by a known method in which an alkali metal compound, an alkaline earth metal compound, or the like is added to the reaction system and a phosphorus compound is further added are used. If the particle content is less than 0.01% by weight, it is difficult to impart lubricity to the film, which is not preferable. Conversely, if it exceeds 1% by weight, PE
When the heat-shrinkable film is dissolved in an alkaline aqueous solution at the time of collecting the T bottle, the particles are likely to adhere to the PET bottle as a residual solution, and if the particles are contained in the collected PET, the water and lactic acid attached to the particles are likely to have an adverse effect. Not preferred. The average particle diameter contained is preferably 0.001.
10 μm, more preferably 0.01 to 2 μm
It is. If the average particle diameter is less than 0.01 μm, it is difficult to impart lubricity, and if it exceeds 10 μm, film defects are likely to occur, which is not preferable.

The polymer used in the heat shrinkable film of the present invention must be mainly composed of polylactic acid. Examples of the polymer mainly composed of polylactic acid include D-lactic acid homopolymer, L-lactic acid homopolymer, D-lactic acid / L-lactic acid copolymer, D-lactic acid / hydroxycarboxylic acid copolymer, and a mixture thereof. Further, the polymer mainly composed of polylactic acid is preferably composed mainly of an L-lactic acid component and has a D-lactic acid component content of 0 to 30% by weight in view of heat resistance and heat shrinkage characteristics. Preferably D
-The content of the lactic acid component is 0 to 20% by weight.

The polylactic acid-based polymer of the film in the present invention can be obtained by the following method. As a raw material, D-lactic acid and / or L-lactic acid can be mainly used, and hydroxycarboxylic acids such as glycolic acid, hydroxybutyric acid, hydroxyvaleric acid and hydroxycaproic acid can be used in combination. Further, dicarboxylic acids and glycols can also be used. The polymer mainly composed of polylactic acid can be obtained by a method of directly dehydrating and polycondensing the above raw material or a method of ring-opening polymerization of the above cyclic ester intermediate. For example, when produced by direct dehydration polycondensation, lactic acids or lactic acids and hydroxycarboxylic acids are preferably azeotropically dehydrated and condensed in the presence of an organic solvent, particularly a phenyl ether solvent, and particularly preferably polymerized by azeotropic distillation. This gives a high molecular weight polymer suitable for the present invention. The molecular weight of the polymer is preferably in the range of 10,000 to 1,000,000 from the viewpoint of moldability as a film.

In the film of the present invention, the polymer mainly composed of polylactic acid includes polyglycolic acid and polybutyric acid polyhydroxybutyrate containing a hydroxycarboxylic acid component, and a dicarboxylic acid component and a glycol component. Polyethylene terephthalate (P
ET), polypropylene terephthalate (PPT), polyethylene-2,6-naphthalate (PEN), polybutylene terephthalate (PBT), polyhexamethylene terephthalate (PHT), polyethylene isophthalate (PEI), polycyclohexane dimethylene terephthalate (PCT) Or a polyester such as polybutylene succinate, or a blend with a copolymer or the like mainly composed of these polyesters. In the case of a copolymer, it may be a random copolymer or a block copolymer. Further, another alkali water-soluble polymer may be added as long as the effects of the present invention are not impaired.

Other alkaline biodegradable polymers include:
For example, cellulose acetate, cellulose, starch, polyvinyl alcohol and the like can be mentioned. When the polymer used for the heat-shrinkable film is a polymer mainly composed of polylactic acid, it can have alkali solubility. The aforementioned polylactic acid-based polymer contains, as necessary, various additives other than particles as long as heat shrinkage, heat shrinkage stress, and alkali solubility are not impaired. Is also good. For example, an organic lubricant such as a flame retardant, an antioxidant, a weathering agent, a heat stabilizer, a lubricant, a crystal nucleating agent, an ultraviolet absorber, a coloring agent, a terminal blocking agent, a fatty acid ester, a wax, or a polysiloxane may be blended. it can.

Further, the heat-shrinkable film of the present invention comprises:
It must be a stretched film. As the stretching method, the inflation simultaneous biaxial stretching method, the stenter simultaneous biaxial stretching method, the biaxial stretching method by any of the stenter sequential biaxial stretching method, the film forming stability, thickness uniformity From the viewpoint, a film formed by a stenter sequential biaxial stretching method is preferable.

Further, the heat-shrinkable film of the present invention comprises:
Heat shrinkage in at least one direction at 120 ° C. is 20%
It is necessary to be above. It is preferably at least 40%. When the heat shrinkage is less than 20%, the heat shrinkage becomes insufficient and the film does not adhere sufficiently to the container, which is not preferable.

The film in the present invention needs to have a maximum heat shrinkage stress of 5.0 MPa or less. Preferably, the maximum heat shrinkage stress in the longitudinal direction is preferably 5.0 MPa or less. If it exceeds 5.0 MPa, the container is easily deformed, which is not preferable.

The heat shrinkable film of the present invention has a pH of 7
It is preferable to dissolve 50% or more in an aqueous solution exceeding 50%.
Preferably, the dissolution is 80% or more, more preferably 95% or more. If it is less than 50%, it is difficult to remove the adhered film at the time of collecting the container, which is not preferable. p
The aqueous solution exceeding H7 is an alkaline aqueous solution, for example, an alkaline aqueous solution such as sodium hydroxide, calcium hydroxide, and ammonium hydroxide. An aqueous solution having a strong alkalinity easily dissolves the film, but too strong an aqueous solution is not preferable because the working environment is deteriorated. Preferably it is pH 7.1-9. pH 7 neutral solution and p
An acidic aqueous solution of less than H7 is not preferable because the film is hardly dissolved. More preferably, an aqueous solution having a pH of more than 7 is heated to 50 ° C. or higher, since the solubility of the film is likely to progress.

In the heat-shrinkable film of the present invention, a polymer mainly composed of polylactic acid can be laminated on a substrate mainly composed of polyester or polyolefin resin.

Here, the polyester is a polymer having a dicarboxylic acid component and a glycol component as constituents.
For example, polyethylene terephthalate (PET), polypropylene terephthalate (PPT), polyethylene-
2,6-naphthalate (PEN), polybutylene terephthalate (PBT), polyhexamethylene terephthalate (PHT), polyethylene isophthalate (PE
Polyester such as I), polycyclohexane dimethylene terephthalate (PCT), polybutylene succinate, or a blend with a copolymer mainly containing these polyesters may be used. In the case of a copolymer, it may be a random copolymer or a block copolymer. The polyolefin resin is a polyethylene or polypropylene resin having an ethylene content of 0.
-6% by weight and propylene, butene-1, hexene-1,
It is a copolymer of 4-methylpentene-1 and octene-1. The copolymer of propylene, butene-1, and octene-1 may be a simple substance, a mixture, or a terpolymer such as propylene and butene-1. The substrate is preferably a polyester such as polyethylene terephthalate or a polyolefin-based resin such as polyethylene or polypropylene, particularly in view of cost and heat resistance. The substrate may be any of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film.
A biaxially stretched film is preferred for obtaining heat shrinkage stress.

In the heat-shrinkable film of the present invention, the base film (A) and the polymer (B) mainly composed of polylactic acid can be laminated in the order of B / A / B.

Although the thickness of the film of the present invention is not particularly limited, it is effectively used at 1 to 300 μm, preferably 5 to 100 μm.

The heat shrinkable film of the present invention is not particularly limited, but can be produced, for example, by the following method. For example, in the case of a biaxially stretched film, the polylactic acid polymer or the polylactic acid copolymer of the above-described composition of the present invention is sufficiently dried using a usual hopper dryer, paddle dryer, vacuum dryer or the like, and then extruded. And melted at 150 to 230 ° C., extruded onto a casting drum by T-die extrusion, and quenched to obtain an unstretched film. As a method to adhere to the casting drum,
Any of an electrostatic application method, an adhesion method using surface tension of water or the like, an air knife method, a press roll method, etc. may be used, but a method of obtaining a film having good flatness and few defects on a smooth surface. It is particularly preferable to use a contact casting method or an electrostatic application method using surface tension of water or the like, since a film having a uniform thickness can be obtained. At this time, the slit width of the die, the discharge amount of the polymer used for the film,
By adjusting the rotation speed of the casting drum, an unstretched film having a desired thickness can be obtained.

Next, a biaxially stretched film can be obtained by simultaneously or sequentially biaxially stretching the unstretched film. In the case of sequential biaxial stretching, the stretching order may be the longitudinal direction of the film, the width direction, or vice versa. Furthermore, in sequential biaxial stretching,
Stretching in the longitudinal direction or the width direction can be performed twice or more. The stretching ratio in the longitudinal direction and the width direction of the film can be arbitrarily set in accordance with the degree of orientation, strength, elastic modulus, and the like, of the heat shrinkage property, heat shrinkage stress property, and adhesion to the container of the target film. Preferably it is 2.0 to 7.0 times. Either the stretching ratio in the longitudinal direction or the stretching ratio in the width direction may be increased, and may be the same. The stretching method is not particularly limited, and methods such as roll stretching and tenter stretching are applied, and the shape may be any shape such as a flat shape and a tube shape. The stretching temperature can be set to a temperature in the range from the glass transition temperature of the polymer mainly composed of polylactic acid to the crystallization temperature. Usually 30-1
20 ° C. is preferred. Further, after the film is biaxially stretched, heat treatment may be performed for the purpose of improving strength, stability over time, and shrinkage characteristics. This heat treatment can be performed by an arbitrary method such as in an oven, on a heat-treated roll, or the like. The heat treatment temperature can be any temperature not lower than the stretching temperature and not higher than the melting point of the polymer mainly composed of polylactic acid, but is preferably not higher than 50 to 150 ° C. The heat treatment time can be arbitrarily set, but it is usually preferable to perform the heat treatment for 1 to 60 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction. The heat-treated film may be rapidly cooled to a glass transition temperature or lower after the heat treatment, or may be cooled stepwise.

[0027]

EXAMPLES Next, the effects of the present invention will be described with reference to examples, but the present invention is not limited to these examples. First, a method for measuring and evaluating a characteristic value will be described below. [Method of Measuring and Evaluating Characteristic Values] The characteristic values of the present invention are determined by the following measuring methods. (1) Slipperiness The slipperiness between the films was determined according to ASTM-D-1894.
The coefficient of static friction (μs) was measured. As a criterion, those with μs of 2.0 or more were evaluated as x, those in the range of 1.6 to 2.0 were evaluated as Δ, and those with less than 1.2 were evaluated as x. (2) Heat Shrinkage Rate and Appearance A sample was cut out in a strip shape of 250 mm in the longitudinal direction of the film and 10 mm in the width direction, and left in an atmosphere at 23 ° C. and a humidity of 60% for 30 minutes.
Two marks are made at intervals of 00 mm, and the distance between the marks is measured using a linear scale length measuring machine, and the value is set to LA. Next, after heating for 5 minutes using hot air of 120 ° C., 23 ° C.,
After cooling for 1 hour in an atmosphere of 60% humidity and controlling the humidity, measure the distance between the marks previously attached with a linear scale length measuring machine.
B. The heat shrinkage is determined by the following equation.

Heat shrinkage = (LA-LB) / LA × 100 Next, the heat shrinkage in the MD and TD directions having an average of 20% or more was evaluated as ○; Less than was evaluated as x. Further, those having appearance defects such as whitening after heat shrinkage were evaluated as x, and those having good appearance were evaluated as ○. (3) Maximum heat shrinkage stress The film was sampled into a strip having a width of 5 mm, and the temperature was increased from room temperature to the melting point of the film at a temperature of 10 ° C. by using a thermal analysis system MTS9000 type and a heat collection stress measuring device TM9400 type manufactured by Vacuum Riko Co. The shrinkage force generated when heated at a rate of / min was measured, and the heat shrinkage stress with respect to temperature was determined. When the maximum heat shrinkage stress is less than 5.0 MPa,
Δ in the range of 6.0 MPa, × in the range of 6.0 MPa or more
Was evaluated. (4) Adhesion to Container After the film was shrunk in a PET bottle (for 1000 ml) with a dryer and packaged, the appearance was evaluated by the following classification. If the film shrinks enough to wrap the container, and the container retains its original shape, ○ indicates that the film shrinks sufficiently to wrap the container, but indicates that the container has some deformed parts. When the shrinkage of the film was insufficient and the container could not be satisfactorily packaged, and when the film shrunk sufficiently to wrap the container but had a clearly deformed portion, the evaluation was evaluated as x. (5) Alkali solubility The film weight of about 5 g is accurately measured, and the value is defined as G1. After immersing in 200 ml of a 2% by weight aqueous sodium hydroxide solution at a temperature of 60 ° C. for 8 hours, the aqueous solution is filtered with filter paper, washed sufficiently with pure water, and the residue on the filter paper is dried at 110 ° C. × 1 hour, and then dried at 23 ° C. After cooling in an atmosphere with a humidity of 60% for 1 hour and humidity control, the weight of the residue is measured and the value is defined as G2. The alkali solubility is determined by the following equation. Alkali solubility = (G1−G2) / G1 × 100
% Or more and less than 95% were evaluated as ○, those of 50% or more to less than 80% as Δ, and those of less than 50% as ×, and the solubility in alkali was evaluated. (6) Container recoverability After shrinking the film into a PET bottle (for 1000 ml) with a drier and packing it, immersing the film in 5000 ml of a 2% by weight aqueous solution of sodium hydroxide at 60 ° C. for 8 hours to dissolve the film, and then dissolving the PET bottle Was removed and washed with water. The recoverability was evaluated by visually classifying the adhesion state of the particles to the PET bottle as follows. The sample having the particles attached to the container was evaluated as x, the sample without the particles was evaluated as ○, and the intermediate product was evaluated as Δ. (7) Comprehensive evaluation Regarding the heat shrinkage stress, heat shrinkage, adhesion to a container, and alkali solubility, practicality as a heat shrinkable film was evaluated as ○, slightly poor as Δ, and poor as ×. did.

Next, the effects of the present invention will be described with reference to examples.

Example 1 Polylactic acid having a weight-average molecular weight of 170,000 and a composition ratio of 95/5 L-lactic acid / D-lactic acid containing 0.15% by weight of wet-process silica particles having an average particle diameter of 1.1 μm After mixing A, the mixture was supplied to a twin-screw extruder and extruded at 200 ° C. into pellets. The pellets were dried at 120 ° C. for 3 hours under reduced pressure, guided to a T-die die using separate extruders, extruded at a temperature of 250 ° C., and cast on a cooling drum to produce a sheet-shaped unstretched film. Next, this sheet is stretched 2.0 times in the longitudinal direction between heating rolls at 65 ° C., cooled, and then guided to a tenter-type stretching machine, heated to a temperature of 60 ° C., and 3.0 times at 70 ° C. in the width direction. After stretching, the film was subjected to a heat treatment at a temperature of 85 ° C., blown with room temperature air onto the film, and cooled to a temperature of 40 ° C. The film is then stretched 1.5 times in the longitudinal direction at 75 ° C., subjected to a heat treatment at 85 ° C., cooled, and subsequently blown with normal temperature air onto the film, cooled to a temperature of 40 ° C., wound up in a roll, and thermally shrunk. Film. The average thickness of the film was 25 μm.

Example 2 0.15 colloidal silica particles having an average particle diameter of 1.1 μm
Weight-average molecular weight 1 wherein the composition ratio of L-lactic acid / D-lactic acid and hydroxycaproic acid is 80/5/15
A heat-shrinkable film was obtained in the same manner as in Example 1 except that 50,000 polylactic acid B was used. The average thickness of the film was 25 μm.

Example 3 Polylactic acid A / 3-hydroxybutyric acid (92 mol%)-3-hydroxyvaleric acid (8 mol%) copolymer containing 0.15% by weight of calcium carbonate particles having an average particle diameter of 1.1 μm With a weight average molecular weight of 170,0 having a blend ratio of 70/30.
A heat-shrinkable film was obtained in the same manner as in Example 1 except that the polylactic acid C of No. 00 was used. Average thickness of film is 25μm
Met.

Examples 4-5, Comparative Examples 1-2 No addition of wet-processed silica particles having an average particle diameter of 1.1 μm (Comparative Example 1), 0.02% by weight (Example 4), 0.8% by weight
(Example 5) A heat-shrinkable film was obtained in the same manner as in Example 1 using polylactic acid A contained at 2% by weight (Comparative Example 2). The average thickness of each film is 25μ
m.

Example 6 Polylactic acid having a weight average molecular weight of 180,000 and a composition ratio of 95/5 to L-lactic acid / D-lactic acid containing 0.15% by weight of wet-process silica particles having an average particle diameter of 1.1 μm A, using a stretching condition of 65 ° C., 2.0 times longitudinal stretching, 70 ° C.,
A film having an average thickness of 25 µm was obtained in the same manner as in Example 1 except that the film was stretched 3.0 times.

COMPARATIVE EXAMPLE 3 Example 1 was repeated except that copolymerized polyethylene terephthalate of 17.5 mol% of isophthalic acid having a weight average molecular weight of 32,000 and containing 0.15 wt% of wet-processed silica particles having an average particle diameter of 1.1 μm was used. In the same manner as in Example 1, a film having an average thickness of 25 μm was obtained.

Comparative Example 4 A film having an average thickness of 25 μm was obtained in the same manner as in Example 1, except that the stretching conditions were only 65 ° C., 1.4-fold longitudinal stretching, and heat treatment at 85 ° C.

Comparative Example 5 The same as Example 1 except that the stretching conditions were only 65 ° C., 1.2 times longitudinal stretching, 70 ° C., 1.5 times transverse stretching, and 85 ° C. heat treatment. To obtain a film having an average thickness of 25 μm. Table 1 summarizes the quality evaluation results of the above heat-shrinkable films.

[0038]

[Table 1]

As can be seen from the results in Table 1, the heat-shrinkable films obtained in Examples 1 to 6 are excellent in heat-shrinkability, heat-shrinkage stress, container adhesion and alkali-soluble. Was.

That is, from Table 1, in order to obtain the above film properties, a stretched film made of a polymer mainly composed of polylactic acid containing 0.01 to 1% by weight of particles,
It was found that the heat shrinkage in at least one direction in hot air at ℃ was 20% or more, and the maximum heat shrinkage stress of the film was 5.0 MPa or less.

On the other hand, the film obtained in Comparative Example 1 had good heat shrinkage and heat shrinkage stress, but was inferior in slipperiness. Although the film obtained in Comparative Example 2 has good heat shrinkage, heat shrinkage stress, and easy lubricity, when dissolved in an aqueous alkali solution at the time of container recovery, particles adhere to the container as residual residues, and The particles were mixed into the recovered PET, and the container was poor in recoverability. The film obtained in Comparative Example 3 had a large heat shrinkage stress, and a portion where the container was deformed was recognized. Comparative Example 4
-The film obtained in Comparative Example 5 did not have sufficient adhesion to the container. None of the films were preferred as heat shrink films.

[0042]

The heat-shrinkable film obtained by the present invention is a stretched film composed of a polymer mainly composed of polylactic acid containing 0.01 to 1% by weight of particles, and is heated in a hot air at 120 ° C. Heat shrinkage in at least one direction at 2
By setting the maximum heat shrinkage stress of the film to 0% or more and 5.0 MPa or less, a heat shrinkable film having excellent heat shrinkage, heat shrinkage stress, and container adhesion and having alkali solubility can be provided.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 67/04 C08L 67/04 // (C08L 67/04 101: 12) B29K 67:00 105: 02 B29L 7:00 F term (reference) 3E086 BA02 BA15 BA33 BA35 BB41 BB67 CA01 4F071 AA22 AA27 AA31 AA41 AA42 AA43 AA49 AB13 AB18 AB21 AB24 AB25 AB26 AC09 AE11 AF05Y AF61Y AH04 BB08 BB09 BC01 BC10 4F210 AA04 RG02 AB01 AB01 RG43 4J002 AB015 AB025 AB045 BC012 BC032 BD152 BE025 BG012 CC032 CC192 CC212 CD002 CF031 CF035 CF045 CF055 CF065 CF085 CF181 CF191 CF212 DD036 DE096 DE136 DE146 DE236 DG046 DG056 DH046 DJ016 DJ036 DJ046 FD 060 FD 050 FD 050 FD 050 FD 050 FD 050 FD 050 FD 050

Claims (8)

[Claims] 1. A stretched film comprising a polymer mainly composed of polylactic acid containing 0.01 to 1% by weight of particles, wherein the film has a heat shrinkage of at least one direction in hot air at 120 ° C. of 20%. %, And the maximum heat shrinkage stress of the film is 5.0 MPa or less. 2. The heat-shrinkable film according to claim 1, wherein the heat-shrinkage ratio of the film in hot air at 120 ° C. in at least one direction is 40% or more. 3. The heat-shrinkable film according to claim 1, wherein the heat-shrinkable film is a stretched film composed of a polymer mainly composed of polylactic acid containing 0.01 to 0.5% by weight of particles. 4. The heat-shrinkable film according to claim 1, wherein the heat-shrinkable film is dissolved in an aqueous solution having a pH of more than 7 by 50% or more. 5. The heat-shrinkable film according to claim 1, wherein the heat-shrinkable film is dissolved in an aqueous solution having a pH of more than 7 by 80% or more. 6. The heat-shrinkable film according to claim 1, wherein the heat-shrinkable film is dissolved in an aqueous solution having a pH of more than 7 by 95% or more. 7. The heat-shrinkable film according to claim 1, wherein the heat-shrinkable film is dissolved by 80% or more with a 2% aqueous sodium hydroxide solution. 8. The heat-shrinkable film according to claim 1, wherein 95% or more of the heat-shrinkable film is dissolved in a 2% aqueous sodium hydroxide solution.