JP2006232929A - Stretched film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stretched film consisting mainly of a plant-derived raw material and having a good transparency, impact resistance and bend-whitening resistance. <P>SOLUTION: This stretched film is obtained by stretching a film consisting of a resin composition containing a lactic acid-based resin and a silicone acrylic compounded rubber in at least one direction is provided by blending ≥1 and ≤40 mass% range silicone acrylic compounded rubber based on the total mass of the lactic acid-based resin and the silicone acrylic compounded rubber. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a stretched film containing a lactic acid-based resin, and particularly relates to a stretched film having good transparency, impact resistance, and bending whitening resistance.

  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. Therefore, there is a demand for materials that do not adversely affect the global environment even when discarded.

  In addition, since petroleum, which is a raw material for ordinary plastics, is a depleting resource, the use of renewable resources is required. For example, plant-derived plastics can be obtained by using renewable non-depleting resources, so it is possible to conserve petroleum-depleting resources such as oil, and after use, they are biodegraded and return to nature. Recyclable.

  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, in particular, lactic acid-based resins are attracting attention as an alternative material for polystyrene and polyethylene terephthalate in the field of injection molding for film packaging materials, home appliances, OA equipment, automobile parts, and the like.

  However, lactic acid-based resins are very brittle materials and difficult to use in fields where impact resistance is required.

  Various studies have been conducted to improve the impact resistance of lactic acid resins. For example, JP-A-9-169896 discloses a biodegradable polymer composition mainly composed of a mixture of two or more of biodegradable polymers of polylactic acid, glycol / aliphatic dicarboxylic acid copolymer and polycaprolactone. JP-A-9-316310 discloses a composition comprising polylactic acid and a modified olefin compound, and JP-A-2000-191895 discloses lactic acid as a main component. A plasticized polylactic acid composition comprising a polymer and an aliphatic polyester plasticizer mainly composed of an aliphatic carboxylic acid and a chain molecular diol is disclosed. A biodegradable resin composition comprising lactic acid and an epoxidized diene block copolymer is disclosed, and Japanese Patent Application Laid-Open No. 2001-031853 discloses polymilk. And a lactic acid polymer composition comprising an aliphatic polyester and polycaprolactone, and Japanese Patent Application Laid-Open No. 2003-183488 discloses at least one rubber selected from crystalline polylactic acid, natural rubber and polyisoprene. A polylactic acid resin composition comprising components is disclosed. However, when a glycol / aliphatic dicarboxylic acid copolymer, polycaprolactone, modified olefin compound, epoxidized diene block copolymer, natural rubber, polyisoprene, etc. are mixed with a lactic acid resin, the impact resistance is improved. Although the effect is seen, the transparency is remarkably impaired, and for example, it is difficult to use it for applications such as packaging materials that require visual confirmation of the contents inside the package.

  Japanese Patent Application Laid-Open No. 2003-286400 discloses at least one selected from styrene units and butadiene units in the shell layer of diene rubber, natural rubber, silicone rubber, methyl methacrylate, or methyl acrylate as an impact modifier. A technique for improving impact resistance by blending a multilayer structure containing a lactic acid resin into a lactic acid resin or the like is disclosed. However, although the silicone rubber has a refractive index close to that of the lactic acid resin, it is difficult to uniformly finely disperse it in the lactic acid resin. Therefore, it is difficult to say that the obtained resin composition is transparent. Further, in a multilayer structure including methyl methacrylate or methyl acrylate in the shell layer and styrene units and / or butadiene units in the core layer, polymethyl methacrylate can be finely dispersed in polylactic acid, Since the refractive index of the styrene unit or butadiene unit and the refractive index of the lactic acid resin are greatly different, transparency is significantly impaired.

  Furthermore, if the resin component other than the lactic acid resin blended to improve the impact resistance is incompatible with the lactic acid resin, a remarkable whitening occurs when the film is bent, so an excellent appearance is required. It cannot be used for certain applications.

JP 09-169896 A JP 09-316310 A JP 2000-191895 A JP 2000-219803 A JP 2001-031853 A JP 2003-183488 A JP 2003-286400 A

  As described above, the conventional method for imparting impact resistance to lactic acid-based resins cannot sufficiently satisfy all of transparency, impact resistance and bending whitening resistance, and a stretched film having all these characteristics. Was desired.

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to have plant-derived raw materials as the main components, have impact resistance, transparency, and whitening due to bending. There is no stretched film to provide.

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 stretched film of the present invention is a stretched film obtained by stretching a film comprising a resin composition containing a lactic acid resin and a silicone acrylic composite rubber in at least one direction, and is a total of the lactic acid resin and the silicone acrylic composite rubber. The silicone acrylic composite rubber is blended in the range of 1% by mass to 40% by mass with respect to 100% by mass.

  The stretched film of the present invention is preferably stretched so that the area ratio is 1.1 times or more and 16.0 times or less.

  The stretched film of the present invention preferably has a haze value of 15% or less at a film thickness of 50 μm and a hydroshot value of 20 kgf · mm or more.

  According to the present invention, a stretched film having improved impact resistance of a lactic acid resin and excellent in transparency and bending whitening property is provided by blending and stretching a silicone acrylic composite rubber with a lactic acid resin. can do.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described below.
The stretched film of the present invention uses a resin composition containing a lactic acid resin and a silicone acrylic composite rubber.

  The lactic acid-based resin 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, and structural units of L-lactic acid and D-lactic acid. These are poly (DL-lactic acid) and 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. 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. In consideration of availability, etc., L-form: D-form = 99.5: 0.5 to 94: 6, or L-form: D-form = 0.5: 99.5 to 6:94. It is preferable.

  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.

Further, if necessary, such as improving heat resistance, a small amount of copolymer component within a range that does not impair the essential properties of the lactic acid resin, for example, within a range containing 90% by mass or more of the lactic acid resin component. Can be added. As a small amount of the copolymer 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.

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

  In the present invention, it is important to blend a silicone acrylic composite rubber in order to improve the impact resistance of the lactic acid resin. Silicone rubber is excellent in low temperature characteristics and has a high effect of imparting impact resistance. Silicone rubber can be finely dispersed in lactic acid resin by compounding with acrylic, so adding silicone acrylic composite rubber to lactic acid resin can greatly improve the impact resistance of lactic acid resin. it can. Examples of the silicone acrylic composite rubber used in the present invention include those commercially available from Mitsubishi Rayon Co., Ltd. under the trade name “Metabrene S-2001”.

  The compounding amount of the silicone acrylic composite rubber is such that the proportion of the silicone acrylic composite rubber is 1% by mass or more and 40% by mass or less, and 5% by mass or more and 30% by mass in the total mass of the lactic acid resin and the silicone acrylic composite rubber. The content is preferably 10% by mass or more and more preferably 20% by mass or less. When the compounding amount of the silicone acrylic composite rubber is 1% by mass or more and 40% by mass or less, impact resistance can be improved without substantially impairing the transparency of the lactic acid resin.

  In the present invention, addition of a heat stabilizer, an antioxidant, a UV absorber, a light stabilizer, a pigment, a colorant, a lubricant, a plasticizer, a nucleating agent, an inorganic filler, etc. within the range not impairing the effects of the present invention. An agent can be blended.

Next, a method for forming a stretched film using a resin composition containing a lactic acid resin and a silicone acrylic composite rubber will be described.
A film can be formed by putting lactic acid resin, silicone acrylic composite rubber, and, if necessary, raw materials such as additives into the same extruder, directly kneading and molding. Alternatively, the dry blended raw material is extruded into a strand shape using a twin-screw extruder to produce pellets, and the pellets are again placed in an extruder to form a film. In addition, since lactic acid-type resin is easy to raise | generate a hydrolysis at the time of melt molding, it is preferable to dry beforehand or pass through a vacuum vent extrusion process.

  Regardless of which method is employed, it is necessary to consider a decrease in molecular weight due to decomposition of the raw material, but the latter is preferably selected in order to uniformly mix the raw materials. For example, lactic acid-based resin and silicone acrylic composite rubber, and if necessary, other additives, etc. are sufficiently dried to remove moisture, and then melt-mixed using a twin screw extruder to form a strand. Extrude to produce pellets. Note 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, and the viscosity of the mixed resin changes depending on the mixing ratio of the lactic acid resin, vegetable oil, cross-linking agent, and other additives. In view of the above, it is preferable to appropriately select the melt extrusion temperature. In practice, a temperature range of 160 ° C. to 230 ° C. is usually selected.

  After pellets prepared by the above method are sufficiently dried to remove moisture, film formation is performed using the method described below.

  That is, a film or a sheet can be formed by a roll stretching method, a tenter stretching method, a tubular method, an inflation method, or the like. In addition, a film or sheet having a thickness greater than that formed by roll stretching or the like can be formed by a T die casting method, a pressing method, or the like.

  In addition, a sheet | seat is a product which is thin on the definition in JIS, and generally the thickness is small and flat instead of length and width. By the way, a film is a thin flat product whose thickness is extremely small compared to the length and width and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll (JIS K 6900). ). Therefore, it can be said that a film having a particularly small thickness among the sheets is a film, but the boundary between the sheet and the film is not clear and is difficult to distinguish clearly. Even when the term “film” is used, “sheet” is also included.

The stretched film of the present invention needs to stretch the film or sheet obtained by the above method in at least one direction. Stretching may be simultaneously performed when a film or sheet is produced by the above method.
In the present invention, “MD” refers to the longitudinal direction of the film (the flow direction of the film), and “TD” refers to the direction orthogonal to the MD. In the present invention, when the film is stretched in only one direction, the stretching direction may be either MD or TD.

  The stretch ratio of the stretched film of the present invention is preferably in the range of 1.1 times or more and 16.0 times or less, more preferably 2.0 times or more and 9.0 times or less in terms of area magnification. . If the area magnification is 1.1 times or more, excellent bending whitening resistance can be imparted by molecular orientation. If the area magnification is 16.0 times or less, the film will not break during stretching.

  The stretched film of the present invention is preferably transparent. For example, the haze value of a film having a thickness of 50 μm measured in accordance with Japanese Industrial Standard JIS K7105 is preferably 15% or less, more preferably 10% or less. It is. If the haze value is 15% or less, the contents can be visually confirmed through the stretched film.

  The stretched film of the present invention preferably has an impact strength by hydroshot method of 20 kgf · mm or more, more preferably 40 kgf · mm or more. If the impact strength is 20 kgf · mm or more, sufficient impact resistance can be exhibited.

The stretched film of the present invention does not whiten when bent. “Excellent bending whitening resistance” means that when the film is bent so that the angle formed by the film is 180 degrees in the same direction as TD, no whitening is visually observed in the bent portion.
Thus, since the stretched film formed using the resin composition of the present invention has excellent transparency, impact resistance, and resistance to bending whitening, transparency, impact resistance, etc. are required. Can be widely used for applications such as transparent bags and packaging materials.

  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, each Example and each comparative example evaluated by the method shown below.

(1) Haze Based on Japanese Industrial Standard JIS K7105, total light transmittance and diffuse transmittance were measured for a stretched film having a thickness of 50 μm, and a haze value was calculated based on the following formula. A film having a haze value of 15% or less in a 50 μm thick film is acceptable.

Haze value = (diffuse transmittance / total light transmittance) × 100

(2) Hydroshot Using a hydroshot impact tester HTM-1 manufactured by Shimadzu Corporation, a 0.5 inch diameter impact core is formed into a stretched film at a speed of 3 m / sec under the condition of a temperature of 23 ° C. The energy required for the collision was calculated. A sheet having a hydroshot value of 20 kgf · mm or more for a sheet having a thickness of 50 μm was regarded as acceptable.

(3) Bending whitening resistance A stretched film was cut into a size of 10 cm × 10 cm to prepare a sample film. This sample film was bent so that the angle formed by the film was 180 degrees in the same direction as TD. At this time, the whitening state of the bent portion was visually observed, the case where whitening was not observed in the bent portion was indicated by the symbol “◯”, and the case where whitening was observed in the bent portion was indicated by the symbol “×”. .

Example 1
Using 95% by mass of Nature Works 4032D (L-lactic acid / D-lactic acid = 98.6 / 1.4, weight average molecular weight 200,000) manufactured by Cargill Dow as a lactic acid-based resin, Mitsubishi Rayon ( 5% by mass of Methbrene S-2001 manufactured by Co. A mixture of Nature Works 4032D and Metabrene S-2001 in a mass ratio of 95% by mass: 5% by mass was kneaded at 200 ° C. using a 40 mmφ single screw extruder, and then extruded from the die. Subsequently, it was rapidly cooled by being brought into contact with a casting roll at 45 ° C. to produce a 200 μm thick sheet. The obtained sheet was passed through a sequential biaxial tenter manufactured by Mitsubishi Heavy Industries, Ltd. and stretched at 75 ° C. in TD at a stretch ratio of 4 to obtain a stretched film having a thickness of 50 μm.
The obtained stretched film was evaluated for haze, hydroshot, and bending whitening resistance. The results are shown in Table 1.

(Example 2)
Example 1 except that the blending ratio of the lactic acid-based resin and the silicone acrylic composite rubber in Example 1 was changed so that the mass ratio would be: Nature Works 4032D: Metablene S-2001 = 90% by mass: 10% by mass A film was prepared in the same manner as described above. Moreover, it extended | stretched similarly to Example 1 and produced the 50-micrometer-thick stretched film.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 1.

(Example 3)
Example 1 except that the blending ratio of the lactic acid-based resin and the silicone acrylic composite rubber in Example 1 was changed so that the mass ratio would be Nature Works 4032D: Metabrene S-2001 = 85% by mass: 15% by mass. A film was prepared in the same manner as described above. Moreover, it extended | stretched similarly to Example 1 and produced the 50-micrometer-thick stretched film.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 1.

Example 4
Example 1 except that the blending ratio of the lactic acid-based resin and the silicone acrylic composite rubber in Example 1 was changed so that the mass ratio would be Nature Works 4032D: Metabrene S-2001 = 70% by mass: 30% by mass. A film was prepared in the same manner as described above. Moreover, it extended | stretched similarly to Example 1 and produced the 50-micrometer-thick stretched film.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 1.

(Example 5)
In Example 1, the lactic acid resin was changed to Nature Works 4060D (L-lactic acid / D-lactic acid = 87.3 / 12.7, weight average molecular weight 200,000), and a blend of the lactic acid resin and the silicone acrylic composite rubber A film was produced in the same manner as in Example 1 except that the ratio was changed so that the ratio was as follows: Nature Works 4060D: Metablene S-2001 = 85 mass%: 15 mass%. Moreover, it extended | stretched similarly to Example 1 and produced the 50-micrometer-thick stretched film.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 1.

(Example 6)
A sheet having a thickness of 450 μm was prepared with the same composition as in Example 1. Subsequently, the obtained film was stretched in the same manner as in Example 1 except that the stretching ratio was changed to TD 3.0 times and MD 3.0 times to produce a stretched film having a thickness of 50 μm.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 1.

(Comparative Example 1)
A film was produced from Nature Works 4032D in the same manner as in Example 1 except that the silicone acrylic composite rubber was not blended in Example 1. Using this film, a stretched film having a thickness of 50 μm was produced in the same manner as in Example 1.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 2.

(Comparative Example 2)
In Example 1, instead of silicone acrylic composite rubber, Bionore 3003 (polybutylene succinate / adipate) manufactured by Showa High Polymer Co., Ltd. was used, and these were in a mass ratio, Nature Works 4032D: Bionore 3003 = 85% by mass: A film was produced in the same manner as in Example 1 except that the content was changed to 15% by mass. Moreover, it extended | stretched similarly to Example 1 and produced the 50-micrometer-thick stretched film.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 2.

(Comparative Example 3)
In Example 1, Ecoflex F (polybutylene adipate / terephthalate) manufactured by BASF was used in place of the silicone acrylic composite rubber, and these were in a mass ratio, Nature Works 4032D: Ecoflex F = 85 mass%: 15 mass% A film was produced in the same manner as in Example 1 except that the change was made. Moreover, it extended | stretched similarly to Example 1 and produced the 50-micrometer-thick stretched film.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 2.

(Comparative Example 4)
In Example 1, Cell Green P-H7 (polycaprolactone) manufactured by Daicel Chemical Industries, Ltd. was used instead of silicone acrylic composite rubber, and these were in a mass ratio, Nature Works 4032D: Cell Green P-H7 = 85 mass %: A film was produced in the same manner as in Example 1 except that the content was changed to 15% by mass. Moreover, it extended | stretched similarly to Example 1 and produced the 50-micrometer-thick stretched film.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 2.

(Comparative Example 5)
In Example 1, instead of silicone acrylic composite rubber, Plumate PD-150 (a copolymer of diol / dicarboxylic acid and polylactic acid) manufactured by Dainippon Ink & Chemicals, Inc. was used, and these were used in a mass ratio, and Nature Works. 4032D: Plamate PD-150 = 85% by mass: A film was produced in the same manner as in Example 1 except that the amount was changed to 15% by mass. Moreover, it extended | stretched similarly to Example 1 and produced the 50-micrometer-thick stretched film.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 2.

(Comparative Example 6)
In Example 1, instead of the silicone acrylic composite rubber, Mitsubishi Rayon Co., Ltd. metabrene C-323A (core-shell type acrylic / butadiene rubber) was used, and these were in a mass ratio, Nature Works 4032D: Metabrene C-323A = 85% by mass: A film was produced in the same manner as in Example 1 except that the content was changed to 15% by mass. Moreover, it extended | stretched similarly to Example 1 and produced the 50-micrometer-thick stretched film.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 2.

(Comparative Example 7)
In Example 1, instead of silicone acrylic composite rubber, Bond First E (ethylene / glycidyl methacrylate copolymer) manufactured by Sumitomo Chemical Co., Ltd. was used, and these were in a mass ratio, Nature Works 4032D: Bond First E = 85 mass. %: A film was produced in the same manner as in Example 1 except that the content was changed to 15% by mass. Moreover, it extended | stretched similarly to Example 1 and produced the 50-micrometer-thick stretched film.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 2.

(Comparative Example 8)
In Example 1, except that the blending ratio of the lactic acid-based polymer and the silicone acrylic composite rubber was changed so that these were in the mass ratio, Nature Works 4032D: Metablene S-2001 = 50 mass%: 50 mass%. A film was produced in the same manner as in Example 1. Moreover, it extended | stretched similarly to Example 1 and produced the 50-micrometer-thick stretched film.
About the obtained stretched film, evaluation similar to Example 1 was performed. The results are shown in Table 2.

(Comparative Example 9)
In Example 3, a film was prepared in the same manner as in Example 3 by using a mass ratio of Nature Works 4032D: methabrene = 85% by mass: 15% by mass, but stretching was not performed.
About the obtained unstretched film, evaluation similar to Example 1 was performed. The results are shown in Table 2.

  As is clear from Table 1, the stretched films of Examples 1 to 6 were found to have a haze value of 15% or less, a hydroshot value of 20 kgf · mm or more, and no whitening when bent. That is, it turned out that the stretched film of Examples 1-6 satisfy | fills all the passing lines of these evaluations.

  On the other hand, as is clear from Table 2, the stretched films of Comparative Example 1 and Comparative Example 5 have a haze value of 15% or less and good folding whitening property, but the hydroshot value is less than 20 kgf · mm. It was found to be inferior in impact resistance.

  Although the stretched film of Comparative Example 2 and Comparative Example 4 gave good results with respect to bending whitening, the hydroshot value was less than 20 kgf · mm, and the impact resistance was poor. Therefore, it was found that not all the characteristics of transparency, impact resistance and bending whitening resistance were satisfied at the same time.

  The stretched films of Comparative Examples 3, 6, 7, and 8 did not whiten when bent, but the haze value was larger than 15% and the transparency was inferior. Therefore, it was found that not all the characteristics of transparency, impact resistance and bending whitening resistance were satisfied at the same time.

The unstretched film of Comparative Example 9 had a haze value of 15% or less and a hydroshot value of 20 kgf · mm or more, but whitening occurred during bending.
Thus, the stretched films of Comparative Examples 1 to 9 did not satisfy all of the above evaluations at the same time, and had practical problems.

The stretched film of the present invention has a plant-derived raw material as a main component, has impact resistance, and is transparent and does not cause bending whitening. Therefore, a sheet, a packaging material, which requires transparency, It can be widely used for applications such as packaging bags.

Claims (3)

  A stretched film obtained by stretching a film composed of a resin composition containing a lactic acid resin and a silicone acrylic composite rubber in at least one direction, and a total mass of the lactic acid resin and the silicone acrylic composite rubber is 100% by mass The stretched film is characterized in that the silicone acrylic composite rubber is blended in the range of 1% by mass to 40% by mass.   The stretched film according to claim 1, wherein the stretched film is stretched so that the area magnification is 1.1 times or more and 16.0 times or less. The stretched film according to claim 1 or 2, wherein the film has a haze value of 15% or less and a hydroshot value of 20 kgf · mm or more at a thickness of 50 µm.