JP2006198931A - Biodegradable laminated film and sealed bag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable laminated film which not only indicates flexibility and impact resistance but also has an appearance excellent in transparency and glossiness, increases the commercial value of an article to be packaged, is capable of a good bag making aptitude by a bag making machine especially when used as a melt-cut sealed bag film for packaging, and prevents the breakage of the bag when contents is put in the obtained sealed bag and the sealed bag obtained by using the laminated film. <P>SOLUTION: The biodegradable laminated film comprises a layer containing poly(butylene succinate adipate) between layers containing polylactic acid. The sealed bag is obtained by melt-cutting/sealing the laminated film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a biodegradable laminated film that is transparent and suitable as a packaging film and has impact resistance and a sealing bag obtained from the laminated film.

  In general, a packaging film is made of a transparent polypropylene or polyethylene terephthalate film so that the contents can be seen well, and a transparent film with higher gloss is required to enhance the display effect of the product. However, the above-mentioned resins such as polypropylene and polyethylene terephthalate can only be disposed of by incineration or landfill after use, and from the viewpoint of environmental protection in recent years, conversion to a material with less environmental load is required.

From the viewpoint of consideration for the environment, biodegradable resins that are finally decomposed into carbon dioxide and water by hydrolysis or biodegradation in soil or water are drawing attention.
In such a biodegradable resin, a hard type having a glass transition point represented by polylactic acid having a glass transition temperature of room temperature or higher has good transparency and meets the requirements of the packaging film, but is a very hard and brittle material. Therefore, the performance as a packaging film is not satisfied.

In order to improve the brittle nature of this polylactic acid, a technique of softening by blending a plasticizer or the like is known (for example, see Patent Document 1). In addition, a technique for improving impact resistance by blending a polylactic acid polymer with a biodegradable aliphatic polyester having a glass transition point of 0 ° C. or less is known (see, for example, Patent Document 2).
However, since a film blended with a plasticizer deteriorates in slipperiness, the adaptability to a bag making machine or the like decreases, or transparency deteriorates due to bleeding of the plasticizer due to long-term storage, which is not practical. Further, when an aliphatic polyester having a glass transition point of 0 ° C. or lower is blended, transparency is impaired, and the requirements for the method film are not satisfied.

  On the other hand, relatively soft biodegradable resins such as aliphatic polyesters and aliphatic-aromatic polyesters having a glass transition point of 0 ° C. or lower, such as polybutylene succinate and polybutylene adipate-terephthalate copolymer, are flexible. However, since it becomes cloudy, it lacks transparency, and lacks cosmetics when applied as a packaging film.

JP-A-7-177826 (pages 1-7) JP-A-9-111107 (page 1-6)

  The present invention is to provide a laminated film having flexibility and impact resistance, suitable as a packaging film having transparency and high gloss, and having a biodegradability, and a sealing bag using the laminated film. is there.

As a result of intensive studies to solve the above problems, the present inventors have found that a film in which an intermediate resin layer made of a specific aliphatic polyester is laminated between layers made of a lactic acid polymer by a coextrusion method is transparent. The present invention is completed by finding a sealing bag that has good gloss, flexibility, impact resistance, can be easily made with a twist bag making machine, and has sufficient practicality. It came to.
That is, the present invention provides a biodegradable laminated film having a layer containing poly (butylene succinate-adipate) between layers containing a lactic acid polymer, and the laminated film is fused and sealed. A seal bag is provided.

  The laminated film of the present invention not only exhibits flexibility and impact resistance, but also has an excellent appearance in terms of transparency and gloss, enhances the commercial value of packaging articles, and is particularly used as a fusing seal bag film for packaging. If it is, the bag making machine can have good bag making suitability, and the bag is not torn when the contents are put into the obtained seal bag.

In the laminated film of the present invention, the resin layer containing a lactic acid polymer constitutes a surface layer and a back surface layer, and is a resin layer having a single layer structure or a multilayer structure, respectively. Such front and back layers are usually the same, but may be different as long as the object of the present invention is achieved. Further, even when the front surface layer and the back surface layer are each multi-layered, they may be different from each other as long as the object of the present invention is achieved.
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 hydroxys. A copolymer with a carboxylic acid or a copolymer of L-lactic acid with another hydroxycarboxylic acid, or a blend thereof, or a polyester component obtained by ester reaction of a dicarboxylic acid and a diol with a lactic acid component. Polymerized ones are mentioned, and polylactic acid whose main structural unit is L-lactic acid is particularly preferable from the viewpoint of film formation stability.
In addition, as a resin layer containing a lactic acid polymer, a polyester component obtained by subjecting a dicarboxylic acid and a diol to an ester reaction in addition to the above lactic acid polymer is used within a range not impairing the object of the present invention. Can do. The content of the polyester component at this time is preferably 30% by weight or less in the resin layer.

  Examples of the hydroxycarboxylic acid, diol, and dicarboxylic acid include hydroxycaproic acids such as glycolic acid, hydroxybutyric acid, and hydroxycaproic acid, and hydroxycarboxylic acids such as cyclic lactones such as caprolactone, butyrolactone, lactide, and glycolide; ethylene glycol, propylene glycol Aliphatic diols such as 1,4-butanediol and 1,4-cyclohexanedimethanol; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid; succinic acid, adipic acid, suberic acid and sebacic acid It is an aliphatic dicarboxylic acid.

  As a resin layer containing a lactic acid-based polymer, the melt flow rate is preferably 0.5 to 20 g / 10 min at 190 ° C., more preferably 2 to 10 g / 10 min, because it needs to have good fluidity during extrusion molding. . When the melt flow rate is within this range, extrusion molding is easy, and when co-extrusion multilayering is performed, a laminated film having good flowability with an adjacent layer and more excellent appearance can be obtained.

In the laminated film of the present invention, the resin layer containing the polybutylene succinate-adipate copolymer is laminated between the resin layers containing the lactic acid-based polymer, and is a resin layer having a single layer configuration or a multilayer configuration. . When the resin layer containing the polybutylene succinate-adipate copolymer is a multilayer, it may be different from each other as long as the object of the present invention is achieved. In addition, the resin layer does not substantially contain a lactic acid polymer, but the resin layer can contain a lactic acid polymer in an amount that does not impair the object of the present invention, that is, 30% by weight or less.
The melt flow rate (190 ° C.) of the resin layer containing the polybutylene succinate-adipate copolymer is preferably about 0.5 to 20 g / 10 min from the point of film extrusion moldability, more preferably 1 to 10 g. / 10 min.

  As the polybutylene succinate-adipate copolymer, for example, polybutylene succinate is copolymerized with adipic acid to reduce the crystallinity, but polybutylene succinate, polybutylene adipate / terephthalate copolymer Polymers and polyesters such as polycaprolactone may be mixed and used as long as the object of the present invention is not impaired. The content of the polybutylene succinate-adipate copolymer in the resin layer is at least 30% by weight.

About the thickness (total thickness) of the laminated film of the present invention, and the thickness of the resin layer containing the front and back layers and the polybutylene succinate-adipate copolymer by the resin layer containing the lactic acid-based polymer, Although it changes with uses etc. and it is not specifically limited, Since the total thickness can be used conveniently as a film for packaging, it is 15-150 micrometers normally, and 20-100 micrometers is especially preferable. The thickness of each of the surface layer and the back layer is preferably 2 to 20 μm, and more preferably 5 μm or more in order to maintain transparency. Further, the thickness of the resin containing the polybutylene succinate-adipate copolymer is essential to be 10 μm or more, and in particular, 10 to 90 μm is preferable from the viewpoint of impact resistance.
The laminated film of the present invention preferably has moderate transparency so as not to impair toughness, and the haze according to JIS K7105 is preferably 20% or less, more preferably 8 to 12%.

  In the laminated film of the present invention, other thermoplastic resins, nucleating agents, thermal stabilizers, antistatic agents, antiblocking agents, slip agents, antifogging agents, etc. are added to any or all of the above resin layers. You may add in the range which does not impair the objective of this invention.

  As a production method of the laminated film of the present invention, it is necessary to be a coextrusion lamination molding method in which the resin layers are laminated adjacent to each other, for example, melt extrusion using two or more extruders, After laminating each resin layer in a molten state by a known coextrusion method such as a coextrusion multilayer die method, a feed block method, etc., a method of processing into a long wound film by a method such as inflation, T-die chill roll method, A coextrusion method using a T die is more preferred.

In the production of the coextruded laminated film of the present invention, the outermost resin layer may be subjected to a surface treatment in order to improve the adhesiveness for printing and the adhesiveness with the adhesive.
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.

  Thus, a sealed bag can be produced by fusing and making the resulting laminated film of the present invention using a bag making machine, preferably a twist bag making machine. In this case, the laminated film is continuously folded in two, preferably by heating and adhering the sealing portion at a heating temperature of 280 to 320 ° C., and fusing. Of course, a sealing bag can be produced by stacking two laminated films appropriately cut out and heating the sealing portion.

  Since the laminated film of the present invention has flexibility and impact resistance characteristics, and has an appearance that is excellent in transparency and gloss, it can be suitably used for packaging articles, particularly packaging sealing bags.

  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
As the surface layer (a) and the back surface layer (c) by the resin layer containing a lactic acid-based polymer, L-lactic acid as a main component [Laisia H-100 manufactured by Mitsui Chemicals, Inc .: melt flow rate 8 g / 10 min] was used. The polybutylene succinate-adipate copolymer-containing resin layer (b) is a polybutylene succinate-adipate copolymer [Showon Polymer Bionore # 3001: Melt Flow Rate 1.4 g / 10 min], surface layer Resin is supplied to each of the extruder for (a) (diameter 30 mm), the extruder for resin layer (b) (diameter 40 mm), and the extruder for back layer (c) (diameter 30 mm), and the extrusion temperature is obtained by coextrusion method. Extrude at 230 ° C. from the T die so that the thickness of each layer (a) / (b) / (c) is 3 μm / 24 μm / 3 μm, cool with a 30 ° C. water-cooled metal cooling roll, Wound into Le, aged in maturing room 35 ° C. 48 h, total thickness was obtained coextruded laminated film of 30μm in the present invention.

Example 2
The coextruded laminated film of Example 2 was prepared in the same manner as in Example 1 except that each layer of (a) / (b) / (c) was extruded to have a thickness of 4.5 μm / 21 μm / 4.5 μm. Obtained.

Comparative Example 1
A coextruded laminated film of Comparative Example 1 was obtained in the same manner as in Example 1 except that polylactic acid mainly composed of L-lactic acid [Lacia H-100 manufactured by Mitsui Chemicals, Inc.] was used as the resin layer (b). .

Comparative Example 2
Example 1 except that polybutylene succinate-adipate copolymer [Bionole # 3001 manufactured by Showa Polymer Co., Ltd.] was used as the surface layer (a), resin layer (b) and back layer (c). A coextruded laminated film of Comparative Example 2 was obtained.

Comparative Example 3
As the surface layer (a), resin layer (b), and back layer (c), polylactic acid mainly composed of L-lactic acid [Lacia H-100 manufactured by Mitsui Chemicals, Inc.] and polybutylene succinate-adipate A coextruded laminated film of Comparative Example 3 was obtained in the same manner as in Example 1 except that the blend [Bionole # 3001 manufactured by Showa Polymer Co., Ltd.] was used by mixing at a weight ratio of 60/40.

The haze, rigidity, impact strength at 0 ° C. and film formability of the obtained coextruded multilayer film were evaluated and measured by the following methods.
(1) Cloudiness: JIS K7105
(2) Rigidity: 1% tangent modulus at 25 ° C. was measured according to ASTM-D882.
(3) 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.
(4) 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 ◯.

  The coextrusion multilayer film obtained was made into a bag-forming property and fusing seal strength by using a twist bag bag making machine HK-40V manufactured by Totani Giken Kogyo Co., Ltd. The bag was made at a fusing blade of 300 ° C. and a bag-making speed of 130 sheets / min to obtain a fusing seal bag. The fusing seal part was cut out to a width of 15 mm, and the fusing seal strength was measured at a tensile speed of 300 mm / min. These results are shown in Table 1.

Claims (5)

Biodegradable laminated film having a layer containing poly (butylene succinate-adipate) between layers containing a lactic acid polymer The biodegradable laminated film according to claim 1, wherein the lactic acid polymer has a melt flow rate of 1 to 20 g / 10 min. The biodegradable laminated film according to claim 1 or 2, wherein the poly (butylene succinate-adipate) has a melt flow rate of 2 to 10 g / 10 min. The biodegradable laminated film according to any one of claims 1 to 3, wherein the haze according to JIS K7105 is 20% or less. A sealed bag formed by fusing and sealing the laminated film according to any one of claims 1 to 4 into a bag shape.