JP4620980B2 - Heat-shrinkable pore-containing film - Google Patents

Description

The present invention relates to a heat-shrinkable film used for applications such as a shrinkable label coated on a plastic container, particularly a beverage PET bottle.

  Plastics are now widely used in every field such as daily life and industry, and the annual production of plastics around the world has reached about 100 million tons. Most of the plastic produced is discarded after use, and this has been recognized as one of the causes of the global environment.

  In recent years, as part of environmental measures, PET can be recycled by separating and recycling plastic containers, especially polyethylene terephthalate (hereinafter sometimes abbreviated as “PET”) containers used for soft drinks. Has become active. When recycling waste plastic, a liquid specific gravity separation method using a buoyancy difference with respect to water or a wind specific gravity separation method using a specific gravity difference of waste plastic is used to separate plastics of different materials. At present, as a material of a heat-shrinkable film widely used for shrink-wrapping plastic containers such as PET, shrink-labels, cap seals, etc., a polyvinyl chloride (hereinafter sometimes abbreviated as “PVC”) resin is used. , Polystyrene (hereinafter sometimes abbreviated as “PS”) resin, or PET resin. For example, even if an attempt is made to fractionate a PET container equipped with a heat-shrinkable film made of a PS resin, the specific gravity of the PET resin is about 1.4, and the specific gravity of the PS resin is 1.03 to 1.06. However, since both are heavier than water, the PET container and the heat-shrinkable film made of PS resin are both submerged in water and the PET container cannot be separated.

  For this reason, the heat-shrinkable film whose specific gravity is less than 1.0 is calculated | required. For example, Japanese Patent Application Laid-Open No. 2002-194110 discloses a heat-shrinkable film using a polyolefin resin such as an ionomer resin having a specific gravity of less than 1.0. According to this publication, separation from a PET container becomes possible, but the heat-shrinkable film thus separated becomes garbage, which promotes shortening of landfill life and damages the natural landscape and the living environment of wild animals and plants. Causes environmental problems. Therefore, there is a need for a heat shrinkable film that does not adversely affect the global environment even when discarded.

  In addition, since petroleum, which is a raw material for plastics such as polyolefin, is a depleting resource, it has become necessary to utilize renewable resources. For example, since plant raw material plastics are obtained by using renewable non-depleting resources, it is possible to save oil-depleting resources such as oil. Moreover, it decomposes back to nature and has excellent biodegradability.

Among plant raw material plastics, lactic acid resins are lactic acid obtained by fermentation of starch, can be mass-produced by chemical engineering, and are excellent in transparency, rigidity, heat resistance and the like. Therefore, lactic acid-based resins are attracting attention in the field of film packaging materials and injection molding as alternative materials such as polystyrene and polyethylene terephthalate.
Therefore, research has been conducted on the use of lactic acid-based resins as materials for heat-shrinkable films and on the weight reduction of these films.

JP 2002-194110 A

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a heat-shrinkable pore-containing film having biodegradability and a specific gravity of less than 1.0. There is.

As a result of intensive studies in view of such a current situation, the present inventors have completed the present invention with high effects.
The heat-shrinkable pore-containing film of the present invention comprises a lactic acid resin (A) and a thermoplastic resin (B) that is incompatible with the lactic acid resin, (A): (B) = 95-60 mass. %: A film formed using a resin composition blended in an amount of 5 to 40% by mass is stretched in at least one direction, and has a bulk specific gravity of 0.50 to 0.99.
Here, the thermoplastic resin (B) incompatible with the lactic acid resin is preferably a polyolefin resin having a storage elastic modulus at 80 ° C. of 0.25 GPa to 2 GPa.
Since the film of the present invention uses a biodegradable lactic acid resin, the utilization of biomass can be promoted and a recycling society can be aimed at.

  The heat-shrinkable pore-containing film of the present invention has a heat shrinkage ratio of 20% or more in the main shrinkage direction after treatment at 80 ° C. for 10 seconds, and a bulk specific gravity after heat shrinkage of 20% at 80 ° C. Is preferably 0.50 to 0.99. A film having such a configuration can be easily separated from PET resin or the like after use.

  According to the present invention, it was possible to provide a heat-shrinkable pore-containing film having biodegradability and a specific gravity of less than 1.0.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described below.
The heat-shrinkable pore-containing film of the present invention is a film made of a resin composition obtained by blending a lactic acid resin (A) and an incompatible thermoplastic resin (B) with the lactic acid resin. However, the blending ratio of the lactic acid resin (A) and the thermoplastic resin (B) needs to be (A) :( B) = 95-60% by mass: 5-40% by mass, and (A ): (B) = 90-70% by mass: 10-30% by mass is preferable. When the blending amount of the thermoplastic resin (B) is less than 5% by mass, the bulk specific gravity of the film after stretching in at least one direction may exceed 1.0, and when it exceeds 40% by mass, Mechanical properties may deteriorate and become brittle.

  The lactic acid-based resin (A) used in the present invention includes poly (L-lactic acid) having a structural unit of L-lactic acid, poly (D-lactic acid) having a structural unit of D-lactic acid, a structural unit of L-lactic acid, and Poly (DL-lactic acid) which is D-lactic acid, or a mixture thereof. Here, the constituent ratio of D-lactic acid (D-form) and L-lactic acid (L-form) in the lactic acid resin is L-form: D-form = 100: 0 to 90:10, or L-form: D-form = 0: 100. -10: 90, and L-form: D-form = 99.5: 0.5-94: 6, or L-form: D-form = 0.5: 99.5-6: 94 Is more preferable. Outside the range where the composition ratio of the L body and the D body is outside the range, the heat resistance of the molded body is difficult to obtain, and the application may be limited.

  As a polymerization method for the lactic acid-based resin, known methods such as a condensation polymerization method and a ring-opening polymerization method can be employed. For example, in the condensation polymerization method, L-lactic acid or D-lactic acid, or a mixture thereof can be directly subjected to dehydration condensation polymerization to obtain a lactic acid resin having an arbitrary composition.

  In the ring-opening polymerization method, a lactic acid-based resin can be obtained from lactide, which is a cyclic dimer of lactic acid, by selecting an appropriate catalyst and using a polymerization regulator as necessary. Lactide includes L-lactide, which is a dimer of L-lactic acid, D-lactide, which is a dimer of D-lactic acid, and DL-lactide composed of L-lactic acid and D-lactic acid. Accordingly, by mixing and polymerizing, a lactic acid resin having an arbitrary composition and crystallinity can be obtained.

Furthermore, a small amount of a copolymer component can be added as necessary to improve heat resistance, for example, within a range containing 90% by mass or more of a lactic acid resin component, A non-aliphatic dicarboxylic acid such as terephthalic acid and / or a non-aliphatic diol such as an ethylene oxide adduct of bisphenol A can be used.
Furthermore, for the purpose of increasing the molecular weight, a small amount of a chain extender such as a diisocyanate compound, an epoxy compound, or an acid anhydride can be used.

Even if the lactic acid-based resin is a copolymer with other hydroxycarboxylic acid units such as lactic acid and / or α-hydroxycarboxylic acid other than lactic acid, it is a copolymer with an aliphatic diol and / or an aliphatic dicarboxylic acid. It may be a polymer.
As other hydroxycarboxylic acid units, optical isomers of lactic acid (D-lactic acid for L-lactic acid, L-lactic acid for D-lactic acid), glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid Bifunctional aliphatic hydroxy-carboxylic acids such as 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, 2-hydroxycaproic acid, etc. Examples include lactones such as caprolactone, butyrolactone, and valerolactone.

  Examples of the aliphatic diol copolymerized with the lactic acid resin include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid.

  The lactic acid resin used in the present invention preferably has a weight average molecular weight in the range of 50,000 to 400,000, more preferably 100,000 to 250,000. When the weight average molecular weight of the lactic acid-based resin is smaller than 50,000, practical physical properties such as mechanical properties and heat resistance are hardly expressed. When it is larger than 400,000, the melt viscosity is too high and the molding processability is poor. Sometimes.

  The lactic acid resin used in the present invention preferably has a Vicat softening point of 50 ° C or higher and 95 ° C or lower. When the Vicat softening point is less than 50 ° C., when the obtained film is used at a temperature slightly higher than room temperature, for example, when used in summer, the film will shrink slightly before use, so-called natural shrinkage. Tends to be large and tends to be a film lacking in dimensional stability. On the other hand, when the Vicat softening point exceeds 95 ° C., it becomes difficult to stretch at a low temperature, and as a result, it becomes difficult to obtain good shrinkage characteristics.

  Typical examples of lactic acid-based resins preferably used in the present invention include commercially available “Lacia” series manufactured by Mitsui Chemicals, Inc., and “Nature Works” series manufactured by Cargill Dow. As mentioned.

  The thermoplastic resin incompatible with the lactic acid-based resin (B) blended in the resin composition according to the present invention has a storage elastic modulus of 0.25 GPa or more when measured at a frequency of 10 Hz and a strain of 0.1%. It is preferably a polyolefin-based resin in a range of 0.0 GPa or less. Examples thereof include highly crystalline homopolypropylene and polymethylpentene having a storage elastic modulus within the above range. When the storage elastic modulus is less than 0.25 GPa, the bulk specific gravity of the resulting heat-shrinkable pore-containing film may exceed 1.0, and when it exceeds 2.0 GPa, the crystallinity is high and the specific gravity is large. It is difficult to obtain.

Other elastomer components can be further blended in the resin composition according to the present invention for the purpose of imparting impact resistance, cold resistance, tear strength and the like. Examples of other elastomer components include styrene elastomers such as styrene-butadiene-styrene copolymers and hydrogenated styrene-butadiene-styrene copolymers, and ethylene / propylene olefin elastomers.
The resin composition according to the present invention may further contain, for example, an aliphatic polyester other than a lactic acid resin, an aromatic aliphatic polyester, and the like, as long as the effects of the present invention are not impaired. Examples of aliphatic polyesters other than lactic acid resins used in the present invention include polyhydroxycarboxylic acids excluding lactic acid resins, aliphatic polyesters obtained by condensing aliphatic diols and aliphatic dicarboxylic acids, and cyclic lactones. Examples include aliphatic polyesters obtained by ring-opening polymerization, synthetic aliphatic polyesters, and aliphatic polyesters biosynthesized in bacterial cells.

  The heat-shrinkable pore-containing film of the present invention needs to be stretched in at least one direction, and pores are formed in the film by stretching to achieve a bulk specific gravity of 0.50 to 0.99. be able to. If the bulk specific gravity of the heat-shrinkable pore-containing film is less than 0.50, the lactic acid-based resin may not be a matrix and a continuous phase may not be formed, and the film may not be stretched. It is. On the other hand, when the bulk specific gravity exceeds 0.99, it approximates the specific gravity of the resin constituting the container to be coated, so when, for example, a PET bottle is shrink-wrapped with a heat-shrinkable pore-containing film, Since it approximates the specific gravity of PET, it becomes difficult to separate by liquid specific gravity separation, and PET cannot be collected separately.

  The heat-shrinkable pore-containing film of the present invention preferably has a heat shrinkage rate at 80 ° C. for 10 seconds of 20% or more in at least one direction. When the heat shrinkage rate is less than 20%, there are cases where a practical function as a heat shrinkable film cannot be exhibited. In order to achieve a heat shrinkage rate of 20% or more, it is necessary to consider the draw ratio and the draw temperature. For example, it is necessary to appropriately adjust the process such as lowering the draw temperature and increasing the draw ratio. There is.

  The heat-shrinkable pore-containing film of the present invention preferably has a bulk specific gravity in the range of 0.50 to 0.99 after being shrunk by 20% at 80 ° C. When the heat-shrinkable pore-containing film of the present invention is used after being contracted by 20%, if the bulk specific gravity is less than 0.50, the lactic acid resin does not become a matrix and a continuous phase cannot be formed. On the other hand, if it exceeds 0.99, it approximates the specific gravity of the container to be coated, for example, the PET resin constituting the PET bottle. Therefore, the container and the heat-shrinkable pore-containing film are separated by liquid specific gravity separation. This is because it becomes difficult to separate and it becomes difficult to separate and collect PET.

  In the resin composition used in the present invention, additives such as a heat stabilizer, an antioxidant, a UV absorber, a light stabilizer, a pigment, and a dye can be formulated as long as the effects of the present invention are not impaired. .

The heat-shrinkable pore-containing film of the present invention can be produced by a film forming method by ordinary melt extrusion. Below, the manufacturing method of the heat shrinkable void | hole containing film of this invention is demonstrated in detail.
The heat-shrinkable pore-containing film of the present invention comprises a lactic acid-based resin, a thermoplastic resin incompatible with the lactic acid-based resin, and, if necessary, other raw materials such as other additives in the same direction biaxial extrusion. It can be produced by precompounding using a machine, a kneader, a Henschel mixer, etc., and then extruding and stretching. Alternatively, after each material is dry blended, it is put into a twin screw extruder, extruded and stretched, or the dry blended material is extruded into a strand shape using a twin screw extruder to produce pellets. Alternatively, the pellets can be put into a twin screw extruder or the like, extruded and stretched.

  Regardless of the method used to form the film, it is necessary to consider the decrease in molecular weight due to the decomposition of the raw materials. However, in order to uniformly mix the raw materials, it is preferable to select a method of dry blending the raw materials. . For example, lactic acid-based resins, thermoplastic resins that are incompatible with lactic acid-based resins, and, if necessary, raw materials such as additives, after sufficiently drying and removing moisture, using a twin screw extruder It is melt mixed and extruded into a strand shape to produce pellets. However, considering that the melting point of the lactic acid resin changes depending on the composition ratio of the L-lactic acid structure and the D-lactic acid structure, the melting point of the mixed resin changes depending on the mixing ratio of the lactic acid resin and other components. Thus, it is preferable to appropriately select the melt extrusion temperature. In practice, a temperature range of 160-230 ° C. is usually selected.

  As the extrusion method, any method such as a T-die method or a tubular method can be employed. The resin melt-extruded in this way is cooled with a cooling roll, air, water, etc., and then reheated by a suitable method such as hot air, hot air, ultraviolet light, carbon dioxide laser, microwave, etc. Stretched biaxially. Here, as a film stretching method, any method such as a roll method, a tenter method, a tubular method, or the like can be employed.

  For example, the pellets produced by the above method are sufficiently dried to remove moisture, and then melt-extruded using a twin screw extruder or the like, and the molten sheet-like resin is stretched with a tenter so that the cavity A heat-shrinkable pore-containing film containing can be produced. Here, since an incompatible thermoplastic resin is blended with the lactic acid-based resin, for example, a sea-island structure is formed in the lactic acid-based resin, and by stretching the sheet-like resin in a molten state, It is considered that voids are formed around the incompatible thermoplastic resin. The specific gravity of the film can be within a predetermined range by the voids formed in this way.

  The stretching temperature is preferably appropriately selected depending on the softening temperature of the lactic acid resin (A) or the thermoplastic resin (B) incompatible with the lactic acid resin, the use required for the film to be formed, etc. In general, the temperature is preferably 60 ° C to 80 ° C, and more preferably 60 ° C to 70 ° C. When the stretching temperature is less than 60 ° C., the elastic modulus of the material in the stretching process becomes too high, and the stretchability tends to decrease, causing the film to break or causing unevenness in thickness. On the other hand, when the stretching temperature is 80 ° C. or higher, desired shrinkage characteristics may not be exhibited, or the bulk specific gravity may be greater than 1.0.

  The draw ratio is preferably selected as appropriate according to the resin composition for forming the film, the stretching means, the stretching temperature, the form required for the resulting film, etc., but is generally 1.5 to 8 times. It is preferable to double. When the draw ratio is less than 1.5 times, appropriate shrinkage characteristics may not be obtained, or the bulk specific gravity often exceeds 1.0. Moreover, it is because the film which a draw ratio exceeds 8 times is hardly needed on actual performance.

Whether the film is uniaxially stretched or biaxially stretched is preferably determined depending on the use of the film to be obtained. For example, when the film is uniaxially stretched, the film is stretched 1.5 to 8 times in the transverse direction (perpendicular to the film flow direction) and 1.01 times in the longitudinal direction (film flow direction). You may perform weak extending | stretching about 1.8 times. When the film is weakly stretched in the machine direction, the mechanical properties of the film can often be improved.
In addition, it is important to quickly cool the film after it has been stretched within a time period in which the molecular orientation of the film does not relax.

  The heat-shrinkable pore-containing film of the present invention may be subjected to corona discharge treatment on one side or both sides as necessary. In addition, the heat-shrinkable pore-containing film of the present invention can be printed on one side or both sides, and any method such as gravure printing can be adopted as a printing method. In the present invention, after the heat-shrinkable pore-containing film is printed, it can be folded so that the printed surface becomes the outer surface, and center-sealed using an organic solvent.

Since the heat-shrinkable pore-containing film of the present invention uses a lactic acid-based resin having biodegradability, it has biodegradability and can protect the environment. In addition, since a film having a specific gravity of less than 1 can be realized, it can be separated from a resin having a specific gravity of more than 1, such as PET, and recycling of PET containers and the like is facilitated.

  The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples, and various applications are possible without departing from the technical scope of the present invention. In addition, the measured value and evaluation which are shown in each Example and each comparative example measured and evaluated by the method shown below.

(1) Bulk specific gravity A film is accurately cut into a size of 10 cm in length and 10 cm in width, and its weight (w) is accurately measured. Moreover, the thickness of the cut-out film is measured at 100 locations, and the average value is obtained as the thickness t (cm). The bulk specific gravity was calculated by dividing the measured weight (w) by the volume (10 × 10 × t) of the film obtained by calculation.

(2) Measurement of dynamic viscoelasticity A sheet made of a measurement target resin (ex. Thermoplastic resin incompatible with lactic acid resin) was accurately cut into a size of 4 mm in width and 60 mm in length to obtain a sample. Using a viscoelastic spectrometer DVA-200 (produced by IT Measurement Co., Ltd.), the measurement temperature was 10 Hz, the strain was 0.1%, the heating rate was 1 ° C./min, and the chuck was 2.5 cm. The dynamic viscoelasticity was measured in the longitudinal direction in the range of 40 ° C to 150 ° C. In addition, as a storage elastic modulus, the storage elastic modulus in 80 degreeC is shown in Table 1.

(3) Thermal contraction rate The film was cut into a size of 100 mm long × 100 mm wide. This was impregnated in a hot water bath at 80 ° C. for 10 seconds, and then the lateral shrinkage was measured. For the thermal shrinkage, the ratio of the amount of shrinkage in the horizontal direction to the original size (100 mm) in the horizontal direction before shrinkage was expressed in%.

(4) Specific gravity after heat shrinkage The film was shrunk by 20% at 80 ° C. and then pulverized. The crushed film piece was floated on water and it was determined whether it floated on water (specific gravity is less than 1). Those that float on the water are indicated by the symbol “◯”, and those that do not float are indicated by the symbol “X”.

(5) Biodegradability (simple compost test)
5 kg of dog food (commercial product) is mixed with 10 kg of horticultural humus in a household conposter (commercial product) set at a temperature of 60 ° C. It was.
On the other hand, a sample piece having a size of 40 mm × 100 mm was cut out from the obtained heat-shrinkable pore-containing film as a test sample and sandwiched between sample holders composed of two 60 mm × 150 mm wire meshes (33 mm eyes). In addition, a thin wire was passed through the mesh to bind the sample pieces. In this way, six test samples were prepared for each example and each comparative example, with the sample piece sandwiched between the sample holders. The six test samples were placed and embedded in the composter soil so that the six test samples were parallel to each other. However, the embedded depth of each test sample was embedded so that the lower bottom surface of the sample holder was 25 mm from the bottom surface of the buried soil, and the upper bottom surface of the sample holder was positioned 25 mm from the surface of the buried soil. . Moreover, 500 mL of water was replenished every day. In this way, the sample piece has been devised so as to suppress collapse and scattering as much as possible by contacting the outside. Two weeks after the embedment, the test sample was taken out, the collapsed state of the sample piece (heat-shrinkable pore-containing film) was observed, and evaluation was performed based on the following criteria.
Evaluation criteria:
〇 Collapsed and no trace.
Δ: There is a slight film residue.
× The shape is maintained without being disassembled.

Example 1
Nature Works 4032D (L-form: D-form = 99: 1, weight average molecular weight 200,000) manufactured by Cargill Dow as a lactic acid resin, and manufactured by Nippon Polypro Co., Ltd. as a thermoplastic resin incompatible with the lactic acid resin Polypropylene resin (trade name “FY6H”). The lactic acid-based resin and the thermoplastic resin were dry blended at a mass ratio of Nature Works 4032D: FY6H = 80 parts by mass: 20 parts by mass. Using a 40 mmφ small-size co-directional twin screw extruder manufactured by Mitsubishi Heavy Industries, Ltd., diisodecyl adipate manufactured by Taoka Chemical Industry Co., Ltd. (hereinafter also abbreviated as DIDA) as a plasticizer from the vent port. While adding 3 parts by mass of 100 parts by mass of the lactic acid resin and the thermoplastic resin, the mixture is kneaded at 200 ° C. and 100 rpm, extruded into a strand shape, rapidly cooled in a water tank, and then cut into pellets. Produced.

The obtained pellets were subjected to a sequential biaxially stretched film tenter manufactured by Mitsubishi Heavy Industries, Ltd. equipped with a 90 mmφ single screw extruder, and the extrusion temperature was 200 ° C., the stretching temperature was 65 ° C., and the direction perpendicular to the flow direction was quadrupled. A uniaxially stretched film having a thickness of 50 μm was obtained by stretching. In addition, weak stretching (1.03 times stretching) was performed in the flow direction (longitudinal direction).
The obtained heat-shrinkable pore-containing film was subjected to measurement and evaluation of bulk specific gravity, dynamic viscoelasticity, heat shrinkage rate, specific gravity after heat shrinkage, and biodegradability. The results are shown in Table 1.

(Example 2)
The lactic acid resin (Nature Works 4032D) used in Example 1 and polymethylpentene 1 (trade name “RT-18”) manufactured by Mitsui Chemicals, Inc. as a thermoplastic resin incompatible with the lactic acid resin. Using. Dry blending was performed at a mass ratio of the lactic acid resin and the thermoplastic resin at a ratio of Nature Works 4032D: RT-18 = 80 parts by mass: 20 parts by mass. Using the same equipment as in Example 1, this was kneaded at 250 ° C. and 100 rpm while injecting DIDA from the vent port with 3 parts by mass of 100 parts by mass of the total amount of lactic acid-based resin and thermoplastic resin. And extruded into a strand shape. This was quenched in a water tank and then cut to form pellets.

A heat-shrinkable pore-containing film having a thickness of 50 μm was produced in the same manner as in Example 1 except that the obtained pellets were used in the same equipment as in Example 1 and the extrusion temperature was changed to 250 ° C.
About the obtained film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

(Comparative Example 1)
The lactic acid-based resin (Nature Works 4032D) used in Example 1 and talc which is hydrous magnesium silicate were used. The lactic acid resin and talc were dry blended at a mass ratio of Nature Works 4032D: talc = 80% by mass: 20% by weight. A 50 μm film was produced from this in the same manner as in Example 1.
About the obtained film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1. In addition, the obtained film had a bulk specific gravity larger than 1.0.

(Comparative Example 2)
A lactic acid resin (Nature Works 4032D) used in Example 1 and a registered trademark Engage (engage 8200) manufactured by Dow Chemical Co., Ltd. were used as the polyolefin elastomer. A lactic acid-based resin and a polyolefin elastomer were dry blended at a mass ratio of Nature Works 4032D: Engage 8200 = 80% by mass: 20% by mass. A 50 μm film was produced from this in the same manner as in Example 1.
About the obtained film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1. In addition, although the shrinkage | contraction characteristic is favorable, the bulk specific gravity of the obtained film was 1.0 or more.

  As is clear from Table 1, the films of Example 1 and Example 2, which are heat-shrinkable pore-containing films of the present invention, have a specific gravity after shrinkage of less than 1, and are easily separated by a liquid specific gravity separation method. I was able to. It was also found to be excellent in biodegradability. Moreover, the film of Example 1 and Example 2 was excellent also in rigidity.

On the other hand, the film of Comparative Example 1 using an inorganic filler instead of a lactic acid resin incompatible with the thermoplastic resin had a specific gravity of the film after shrinkage of greater than 1, so it should be separated by a liquid specific gravity separation method. I couldn't. In addition, the film of Comparative Example 2 using a polyolefin elastomer having a storage elastic modulus of less than 0.25 GPa had a specific gravity after shrinkage of greater than 1 and poor biodegradability.

Claims (4)

Resin composition containing lactic acid resin (A) and thermoplastic resin (B) incompatible with lactic acid resin (A) :( B) = 95-60 mass%: 5-40 mass% Is stretched in the range of 1.5 times to 8 times in the horizontal direction and 1.01 times to 1.8 times in the longitudinal direction, and the heat shrinkage ratio after treatment at 80 ° C. for 10 seconds is A heat-shrinkable pore-containing film having a bulk shrinkage of 20% or more and a bulk specific gravity of 0.50 to 0.99 .   2. The heat-shrinkable empty resin according to claim 1, wherein the thermoplastic resin (B) incompatible with the lactic acid-based resin is a polyolefin-based resin having a storage elastic modulus at 80 ° C. of 0.25 GPa to 2 GPa. Hole-containing film.   The heat-shrinkable pore-containing film according to claim 1 or 2, wherein the thermoplastic resin (B) incompatible with the lactic acid resin is a polypropylene resin. A beverage container comprising the heat-shrinkable pore-containing film according to any one of claims 1 to 3 .