JP2006326858A - Biodegradable non-stretched laminated film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable non-stretched laminated film having biodegradability, flexibility, impact resistance and sealing strength and suitable as a packaging film high in haze, low in glossiness and having a matte appearance. <P>SOLUTION: The biodegradable non-stretched laminated film has a surface layer (1), an intermediate layer (2) and a back layer (3) or the surface layer (1) and the back layer (3). The surface layer (1) contains a lactic acid type polymer, an aliphatic polyester and an inorganic filler and the ratio of the lactic acid type polymer and the aliphatic polyester is 25-40/75-60 wt.%. The back layer (3) comprises at least one kind of the aliphatic polyester with a glass transition temperature of -20°C or below and its glass transition temperature Tn is -50°C≤Ta≤-20°C (Ta: the sum total of the glass transition temperatures corresponding to the weight ratio of aliphatic polyesters different in glass transition temperature). The intermediate layer (2) comprises at least one kind of an aliphatic polyester with a glass transition temperature of -20°C or below. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention has high haze, low gloss, matte appearance and soft texture, and has flexibility, impact resistance and sealing strength suitable for packaging films (matte) biodegradable non-stretched The present invention relates to a laminated film.

  In general, films using resin materials such as polypropylene, polyethylene, and polyethylene terephthalate are devised to print specific characters and patterns using printing ink to enhance the display effect of products. in use. These applications have different performance requirements, and films suitable for them have been developed. For example, it is said that a matte film with a matte appearance with reduced gloss has a moist and soft texture in the packaging industry and has the effect of enhancing the attractiveness and willingness to purchase products. Is required by. Matte film has a sandblasting method in which hard granular sand is sprayed on the film surface, a method in which the film surface is eroded and roughened with an acid or alkali solvent, a method in which inorganic particles or organic synthetic resins are contained in the film resin, etc. It was general. However, resins such as polypropylene and polyethylene terephthalate can only be disposed of by incineration or landfill after use. From the viewpoint of environmental protection in recent years, the amount of combustion heat is low, biodegradation by microorganisms, etc., and composting treatment in compost is possible. There is a need to switch to a resin with a low environmental impact.

  Among the biodegradable resins, polylactic acid is a plant-derived raw material obtained by polymerizing lactic acid obtained by fermenting various starches and sugars, and has low combustion heat. As a polymer raw material that can be recycled on a scale, it is attracting attention for various uses. In such a biodegradable resin, a hard type having a glass transition temperature represented by polylactic acid having a glass transition temperature of room temperature or higher is a very hard and brittle material and does not satisfy the performance as a packaging film. In order to improve the flexibility and impact resistance required during packaging and transportation, a soft biodegradable resin with a glass transition temperature of 0 ° C or less is blended with a polylactic acid polymer to improve flexibility and impact resistance. An attempt has been made.

For example, it is a laminated film A layer made of a polylactic acid polymer, and at least one of the outer layers is B made of a polylactic acid polymer (60 to 90% by mass) and a biodegradable aliphatic polyester (10 to 40% by mass). A polylactic acid-based biaxially stretched laminated film having a high haze and a matte tone containing a layer is disclosed (see, for example, Patent Document 1).
However, the laminated film needs to be biaxially stretched. This is because the main component is a polylactic acid-based polymer, and it is very hard and brittle as it is, so that it is necessary to impart flexibility and impact resistance by biaxial stretching.
Products using polylactic acid polymers and biodegradable aliphatic polyester blends, specifically, a laminated film that has a high haze, low gloss, matte appearance, and is suitable for packaging with flexibility and resistance. A biodegradable unstretched laminated film having impact properties and seal strength has not yet been obtained.

JP 2004-306286 A

  The present invention can be disposed of in the soil after use and easily biodegraded and processed, has flexibility, impact resistance and sealing strength, and has a high tone, low gloss and matte tone. Another object of the present invention is to provide a biodegradable unstretched laminated film suitable as a packaging film.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that at least one or more specific raw materials are present in the surface layer composed of a lactic acid-based polymer, a biodegradable aliphatic polyester, and an inorganic filler, and the back surface layer. An unstretched film obtained by laminating a layer composed of degradable aliphatic polyester, the same aliphatic polyester as the back layer, or an intermediate layer composed of at least one specific aliphatic polyester by a coextrusion method. The inventors have found that this can be solved, and have completed the present invention.

  That is, the present invention has a surface layer (1) and an intermediate layer (2) and a back layer (3), or has a surface layer (1) and a back layer (3), and the surface layer (1 ) Contains a lactic acid-based polymer, an aliphatic polyester, and an inorganic filler, and the ratio of the lactic acid-based polymer / the aliphatic polyester is 25 to 40/75 to 60% by weight. ) Comprises at least one aliphatic polyester having a glass transition temperature of -20 ° C. or lower, and a glass transition temperature Tn of −50 ° C. ≦ Ta ≦ −20 ° C. (Ta: an aliphatic polyester having a different glass transition temperature) Biodegradable unstretched laminate, wherein the intermediate layer (2) is made of at least one aliphatic polyester having a glass transition temperature of -20 ° C or lower. Related to film.

  The biodegradable laminated film of the present invention not only exhibits flexibility and impact resistance characteristics, but also has high haze, low gloss, matte appearance, and soft texture, and has the commercial value of packaging articles. In particular, when used as a packaging film, packaging with good sealing strength is possible, the bag is not torn during transportation from the packaging, and the contents are excellently protected.

  In the biodegradable laminated film of the present invention, the surface layer (1) used contains a lactic acid polymer, an aliphatic polyester, and an inorganic filler, and the lactic acid polymer / the aliphatic polyester. The weight percent ratio is 25-40 / 75-60, preferably 30-35 / 70-65. When the content ratio of the lactic acid-based polymer is in the above range, a laminated film having high haze and low gloss, mat-like flexibility and impact resistance can be obtained. The surface layer (1) is a resin layer having a single layer structure or a multilayer structure.

  The lactic acid-based polymer is not particularly limited, but poly (D-lactic acid), poly (L-lactic acid), a copolymer of D-lactic acid and L-lactic acid, D-lactic acid and other hydroxycarboxylic acids. Examples thereof include copolymers with acids, copolymers of L-lactic acid with other hydroxycarboxylic acids, and blends thereof, and poly (L-lactic acid) whose main structural unit is highly crystalline in view of film formation stability. The lactic acid-based polymer preferably has a melt flow rate of 0.5 to 20 g / 10 min, more preferably 2 to 10 g / 10 min because it is necessary to impart good fluidity to the surface layer (1).

The aliphatic polyester is not particularly limited, but is a polyester obtained by ester reaction of hydroxycarboxylic acid, diol and dicarboxylic acid.
Examples of the hydroxycarboxylic acid, diol, and dicarboxylic acid include hydroxycarboxylic acids such as glycolic acid, hydroxybutyric acid, hydroxycaproic acid and the like, and cyclic lactones such as caprolactone and butyrolactone; ethylene glycol, propylene glycol, 1, Aliphatic diols such as 4-butanediol and 1,4-cyclohexanedimethanol; aliphatic dicarboxylic acids such as succinic acid, adipic acid, suberic acid, and sebacic acid.
The aliphatic polyester has a glass transition temperature of −20 ° C. or lower. Specifically, for example, polybutylene succinate, polybutylene succinate / adipate copolymer, polycaprolactone / butylene succinate copolymer Etc. In addition, from the viewpoint of kneadability with the lactic acid-based polymer and extrudability of the film, the aliphatic polyester preferably has a melt flow rate of about 0.5 to 20 g / 10 min, more preferably 1 to 10 g / min. is there. Such aliphatic polyesters may be used alone or in admixture of two or more.

In the surface layer (1), an inorganic filler such as talc is kneaded and mixed, thereby causing the crystallization promoting effect of the surface layer (1) at the time of film formation to suppress sticking to the cooling roll and the guide roll, The slipperiness on the roll is improved and a stable film forming property is obtained. Examples of the inorganic filler include general inorganic materials such as talc, silica, calcium carbonate, kaolin, oxidized zeolite, and clay.
The inorganic filler is preferably used in an amount of 2 to 15 parts by weight, more preferably 5 to 10 parts by weight, based on a total of 100 parts by weight of the lactic acid-based polymer and the aliphatic polyester. If the content of the inorganic filler is in the above range, the crystallization promotion effect becomes remarkable, and problems in film formation such as stickiness to the cooling roll can be reduced, and the flexibility and resistance of the whole unstretched laminated film can be reduced. Since it is excellent in impact properties, it is more practical as a packaging film.

The back layer (3) of the biodegradable laminated film of the present invention contains at least one aliphatic polyester having a glass transition temperature of −20 ° C. or lower and a glass transition temperature Ta of −50 ° C. ≦ Ta ≦ −20 ° C. (Ta: the sum of glass transition temperatures depending on the weight ratio of aliphatic polyesters having different glass transition temperatures), preferably a single layer configuration or a multilayer configuration of −45 ° C. ≦ Ta ≦ −30 ° C. It is a resin layer. In the present invention, when the back layer is composed of a plurality of aliphatic polyesters having a glass transition temperature of −20 ° C. or lower and different glass transition temperatures, the weight percentage of each aliphatic polyester is multiplied by the respective glass transition temperature. The total glass transition temperature is defined as the glass transition temperature Ta of the back layer (3). Therefore, when only one type of aliphatic polyester is used, the amount is 100%, and Ta is the glass transition temperature of the aliphatic polyester.
If the glass transition temperature Ta is less than −50 ° C., the cooling roll and other guide rolls become sticky and the like becomes difficult to form, and if it exceeds −20 ° C., the back layer (3) is flexible. The impact resistance strength of the whole unstretched laminated film is lowered. Moreover, the sealing start temperature rises and the packaging temperature range becomes narrow, which is inconvenient as a packaging film.

  The aliphatic polyester used in the back surface layer (3) has a constituent component and a melt flow rate in the range described in the surface layer (1), and is used so as to have the glass transition temperature Ta. In order to obtain flexibility as a whole unstretched laminated film and sealing strength as a back layer, those having a low glass transition temperature are preferred. For example, polybutylene succinate, polybutylene succinate / adipate copolymer, polycaprolactone, polycaprolactone / Butylene succinate copolymer and the like. Such aliphatic polyesters may be used alone or in combination.

The intermediate layer (2) of the biodegradable laminated film of the present invention contains at least one aliphatic polyester having a glass transition temperature of −20 ° C. or lower, and preferably has a glass transition temperature Tb. −65 ° C. ≦ Tb ≦ −20 ° C. (Tb: sum of glass transition temperatures according to the weight ratio of aliphatic polyesters having different glass transition temperatures), more preferably a single unit consisting of −60 ° C. ≦ Tb ≦ −35 ° C. It is a resin layer having a layer structure or a multilayer structure. When the intermediate layer is composed of a plurality of aliphatic polyesters having a glass transition temperature of −20 ° C. or lower and having different glass transition temperatures, the weight percentage of each aliphatic polyester is multiplied by the respective glass transition temperatures and summed. When the glass transition temperature is defined as the glass transition temperature Tb of the intermediate layer (2) and only one kind of aliphatic polyester is used, it is 100%, and Tb is the glass transition temperature of the aliphatic polyester. . The intermediate layer (2) is preferably provided when adjusting the physical properties of the obtained laminated film, that is, higher flexibility and strength, and can be omitted.

  The aliphatic polyester used in the intermediate layer (2) has a component and a melt flow rate in the range described in the surface layer (1), and is used so as to have the glass transition temperature Tb. The same resin as phase (3), or a different resin is used alone or as a mixture. In order to obtain flexibility and impact resistance, the intermediate layer of the unstretched laminated film is preferably one having a relatively low crystallization temperature, such as polybutylene succinate / adipate copolymer, polycaprolactone, polycaprolactone / butylene succinate. A copolymer is mentioned. Further, an aliphatic-aromatic polyester-based polybutylene adipate / terephthalate copolymer may be mixed and used within a range not detracting from the object of the present invention.

The thickness (total thickness) of the biodegradable laminated film of the present invention is not particularly limited and may be appropriately set depending on the application, required performance, etc., but the total thickness of about 20 to 100 μm is preferable as the packaging film. . The thickness of the surface layer (1) comprising a lactic acid polymer, an aliphatic polyester and an inorganic filler is preferably 3 μm or more in order to obtain high haze and matting properties. From the standpoint of maintaining impact, 3 to 30 μm is more preferable.
Moreover, the thickness of the intermediate layer (2) is preferably 8 μm to 60 μm, and the thickness of the back surface layer (3) is preferably 4 μm to 40 μm.
The laminated film of the present invention preferably has a haze of 50% or more, more preferably 55 to 80%. The laminated film of the present invention desirably has an appropriate gloss so as not to impair the printability, and the gloss is preferably 5 to 20%, more preferably 8 to 16%.

The biodegradable laminated film of the present invention has another thermoplastic resin, a nucleating agent, a heat stabilizer, a charge on any or all of the surface layer (1), intermediate layer (2), and back layer (3). You may add an inhibitor, an antiblocking agent, a lubricant, an antifogging agent, etc. in the range which does not impair the objective of this invention.

  The 1% secant modulus according to ASTM-D882 of the biodegradable laminated film of the present invention is preferably 0.3 GPa or more and 0.9 GPa or less, and more preferably 0.4 to 0.8 GPa. If the 1% secant modulus is smaller than the above range, the film will lose its elasticity, and the packaging speed will be reduced on the packaging / bag making machine. If it exceeds the above range, it will become hard and brittle as an unstretched laminated film, and during packaging and transportation. Bag breakage is likely to occur.

  In the production of the biodegradable laminated film of the present invention, the surface layer (1) and the intermediate layer (2) and the back layer (3) or the surface layer (1) and the back layer (3) are laminated adjacently. A so-called coextrusion method is preferred. For example, each resin layer is laminated in a molten state by a known coextrusion method such as a coextrusion multilayer die method, a feed block method, etc., which is melt extruded using a plurality of extruders, an inflation method, a T die / cast roll method, etc. A processing method of continuously forming a film by a known method is preferable, and a coextrusion method using a T die is more preferable. The temperature conditions at that time vary depending on the components of the surface layer (1), the intermediate layer (2) and the back layer (3) to be used. For example, the extruder cylinder temperature is 150 to 230 ° C and the T die temperature is 230 ° C. Then, the mixture is melt-kneaded, co-extruded, cooled with a cast roll controlled at 20 to 50 ° C., and then wound up.

In the production of the biodegradable coextruded laminated film of the present invention, the surface layer (1) may be subjected to a surface treatment in order to improve printability and adhesiveness.
The surface treatment method is preferably a corona discharge treatment that can continuously treat the coextruded laminated film of the present invention, can be easily carried out before winding during film formation, and can arbitrarily adjust the degree of treatment. As for the surface treatment, an effect promoting method such as corona discharge or plasma discharge may be used under heating or in an inert gas atmosphere.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these. In the examples, all parts and% are based on weight.

Example 1
The biodegradable resin layer has a three-layer structure of a surface layer (1), an intermediate layer (2), and a back layer (3), and L-lactic acid is mainly used as a lactic acid-based polymer for the surface layer (1) [Mitsui Chemicals, Inc. Laissia H-100 manufactured by Co., Ltd .: Polybutylene succinate / adipate copolymer having a glass transition temperature of −45 ° C. [Bionor # 3001: Showa Polymer Bionore # 3001: Melt Flow Rate 1.4 g / 10 min] is mixed at a weight ratio of 34/66, and 10 parts by weight of talc (manufactured by Matsumura Sangyo) is blended with 100 parts by weight of this mixture. It was melt kneaded and a polylactic acid-aliphatic polyester compound raw material was prepared at an extrusion temperature of 230 ° C. Further, the polybutylene succinate / adipate copolymer [Bionole # 3001 manufactured by Showa Polymer Co., Ltd.] was used as the aliphatic polyester for the intermediate layer (2) and the back phase (3).

  Next, the polylactic acid-aliphatic polyester compound raw material is dried and supplied to the surface layer (1) extruder (caliber 30 mm), and the intermediate layer (2) extruder (caliber 40 mm) and the back layer ( 3) Each raw material is supplied to an extruder for extrusion (diameter 30 mm), and the thickness of each layer (1) / (2) / (3) from the T die at an extrusion temperature of 230 ° C. is 4. Extruded to 5 μm / 16.5 μm / 9 μm, cooled and solidified with a cast roll having a surface temperature of 30 ° C., wound around a paper tube, and aged in a ripening room at 35 ° C. for 48 hours. A biodegradable coextruded unstretched laminated film was obtained.

Example 2
Polycaprolactone / butylene succinate copolymer [Daicel Chemical Industries Cell Green CBS171: Melt Flow Rate 0.9 g / 10 min] and glass transition temperature as aliphatic polyester of the back layer (3) having a glass transition temperature of −41 ° C. (1) / (2) / (3) using polycaprolactone at a temperature of -64 ° C. [Daicel Chemical Industry Cell Green PH7: Melt Flow Rate 1.7 g / min] in a dry blend ratio of 70/30. A coextruded unstretched laminated film of Example 2 was obtained in the same manner as in Example 1 except that the layers were extruded so that the thickness of each layer was 7.5 μm / 13.5 μm / 9 μm /.

Comparative Example 1
As the resin used for the surface layer (1), the same polylactic acid mainly composed of L-lactic acid as in Example 1 [Lacia H-100 manufactured by Mitsui Chemicals, Inc.] and polybutylene succinate / adipate copolymer [Showa Polymer Coextruded unstretched laminated film of Comparative Example 1 was obtained in the same manner as Example 1 except that the mixing ratio with Bionole # 3001] was 60/40.

Comparative Example 2
The coextrusion non-extrusion of Comparative Example 2 was carried out in the same manner as in Example 1 except that polycaprolactone having a glass transition temperature of -64 ° C. [Cell Green PH7 manufactured by Daicel Chemical Industries, Ltd.] was used as the aliphatic polyester of the back layer (3). A laminated film was obtained.

Comparative Example 3
Implemented except that the same polylactic acid (Mitsui Chemicals, Inc., Lacia H-100), which is mainly composed of L-lactic acid as used for the front surface layer (1), was used for the intermediate layer (2) and the back surface layer (3). The biodegradable co-pressed unstretched laminated film of Comparative Example 3 was obtained in the same manner as Example 1.

  The glass transition temperature (Tg) of the aliphatic polyester was measured according to JIS-K7121 using a differential scanning calorimeter (DSC6200) manufactured by Seiko Instruments Inc.

The haze, glossiness, 1% secant modulus at 23 ° C., impact strength at 0 ° C. and film formability of the obtained coextruded unstretched laminated film were evaluated and measured by the following methods.
(1) Haze: JIS-K7105
(2) Glossiness: JIS-K7105
(3) 1% secant modulus: ASTM-D882
(4) Impact strength: A film conditioned for 6 hours in a temperature-controlled room adjusted to 0 ° C. was measured on the spot by the film impact method.
(5) Film formability: A film breakage or film wrapping occurred during film formation was marked with x, and a film with good film formability was marked with ◯.
These results are shown in Table 1.

The resins used in the table are as follows.
Lactic acid-based polymer: A (Laissia H-100 manufactured by Mitsui Chemicals)
Aliphatic polymer: B (Bionore # 3001 manufactured by Showa Polymer)
C1 (Daicel Chemical Industries Cell Green CBS171)
C2 (Daicel Chemical Industries Cell Green PH7)

* Glass transition temperature Ta = (− 41 ° C. × 70%) + (− 64 ° C. × 30%)
100%

  The biodegradable laminated film of the present invention has flexibility and impact resistance characteristics, and also has a high-haze, low-gloss, matte appearance and soft texture, so it can be used for packaging foods, pharmaceuticals, industrial products, etc. It can be suitably used as a material for use.

Claims (8)

It has a surface layer (1) and an intermediate layer (2) and a back surface layer (3), or has a surface layer (1) and a back surface layer (3), and the surface layer (1) is a lactic acid-based polymer. It contains an aliphatic polyester and an inorganic filler, and the ratio of the lactic acid polymer / the aliphatic polyester is 25 to 40/75 to 60% by weight, and the back layer (3) has a glass transition temperature − It is composed of at least one aliphatic polyester having a temperature of 20 ° C. or less, and has a glass transition temperature Tn of −50 ° C. ≦ Ta ≦ −20 ° C. (Ta: glass corresponding to the weight ratio of the aliphatic polyester having a different glass transition temperature) A biodegradable unstretched laminated film, wherein the intermediate layer (2) is made of at least one aliphatic polyester having a glass transition temperature of -20 ° C or lower. The biodegradable unstretched laminated film according to claim 1, wherein the aliphatic polyester in the surface layer (1) has a glass transition temperature of -20 ° C or lower. The biodegradable unstretched laminated film according to claim 1 or 2, wherein the lactic acid polymer / aliphatic polyester weight percent ratio is 25 to 40/75 to 60. The intermediate layer (2) has a glass transition temperature represented by −65 ° C. ≦ Tb ≦ −20 ° C. (Tb: sum of glass transition temperatures depending on the weight ratio of aliphatic polyesters having different glass transition temperatures) The biodegradable unstretched laminated film according to any one of claims 1 to 3, which exhibits Tb). The biodegradable unstretched laminate according to any one of claims 1 to 4, wherein the inorganic filler is contained in an amount of 2 to 15 parts by weight with respect to a total of 100 parts by weight of the lactic acid-based polymer and the aliphatic polyester. the film. The raw polyester according to any one of claims 1 to 5, wherein the aliphatic polyester in the intermediate layer (2) and the back layer (3) is a polyester obtained by ester reaction of hydroxycarboxylic acid, diol and dicarboxylic acid. Degradable unstretched laminated film. The biodegradable unstretched laminated film according to any one of claims 1 to 6, wherein the surface layer (1) has a thickness of 3 µm or more. The biodegradable unstretched laminated film according to any one of claims 1 to 7, wherein a 1% secant modulus according to ASTM-D882 is 0.3 to 0.9 GPa.