JP2002234117A - Heat shrinkable film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable film-like article suitable for shrink packaging, shrink bundling packaging, a shrinkable label or the like and excellent in all of breaking resistance, impact resistance and transparency. SOLUTION: The heat-shrinkable film-like article comprises a laminate having a layer, which comprises a resin composition based on a polylactic acid type polymer and an aromatic/aliphtic polyester resin, and a layer based on the polylactic acid type polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable film, and more particularly to a heat-shrinkable film excellent in transparency and impact resistance, suitable for shrink wrapping, shrink-wrapping wrapping, shrink label, and the like. .

[0002]

2. Description of the Related Art Heat shrinkable films used for shrink wrapping, shrink bundling wrapping, shrink labels, etc. are made of polyvinyl chloride (PVC), styrene-butadiene block copolymer (SBS), It is known that a main material is a polyester resin or the like. These are widely used, but when they are discarded after use, they remain and accumulate without being substantially decomposed because they are chemically stable and have no biodegradability. Therefore, the capacity of the garbage disposal site is saturated in a short period of time. Therefore, a biodegradable material that has a low heat of combustion and is safe for the human body or the like has been demanded, and much research has been made. As one of them, polylactic acid is known. Polylactic acid has a combustion calorie less than half that of polyethylene, and hydrolyzes naturally in soil or water, and then becomes a harmless degradation product by microorganisms. JP-A-5-221790 discloses a heat-shrinkable film made of polylactic acid.
Since it is as high as 150 ° C., it can be used only for special purposes. Originally, polylactic acid films and sheets are brittle due to the inherent brittleness of the material and have poor impact resistance,
Difficult for practical use. In particular, when a shrinkable film is formed by uniaxial stretching, the brittleness in the direction in which the film is not stretched is not improved. In order to improve this, a method of blending an aliphatic polyester is known. According to such a method, although good results are obtained in rupture at low speeds (rupture resistance) such as a tensile test, it is weak against instantaneous impact (impact resistance) and tears. There was a problem. Therefore, a heat-shrinkable polylactic acid-based film having excellent impact resistance has been demanded for a substantially uniaxially stretched film containing polylactic acid as a main component.

[0003]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, have completed the present invention. That is, the heat-shrinkable film-like product of the present invention is a laminate having a layer composed of a resin composition mainly containing a polylactic acid-based polymer and an aromatic aliphatic polyester resin and a layer mainly containing a polylactic acid-based polymer. It is characterized by being a body. The heat-shrinkable film according to another embodiment of the present invention is a layer composed of a resin composition containing a polylactic acid-based polymer and an aromatic aliphatic polyester resin as a main component, and a layer containing a polylactic acid-based polymer as a main component. Characterized by being stretched in at least one direction. The heat-shrinkable film-like material of another embodiment of the present invention has, as an inner layer, at least one layer made of a resin composition containing a polylactic acid-based polymer and an aromatic aliphatic polyester resin as main components, and as an outer layer,
A laminate having at least one layer mainly composed of a polylactic acid-based polymer is stretched in at least one direction. Here, the aromatic aliphatic polyester resin may include an aliphatic dicarboxylic acid component, an aromatic dicarboxylic acid component, and an aliphatic diol component. Further, the aromatic aliphatic polyester resin may contain an aromatic dicarboxylic acid component in a range of 50 mol% or less.

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The heat-shrinkable film of the present invention is a laminate having a layer composed of a resin composition containing a polylactic acid-based polymer and an aromatic aliphatic polyester as a main component and a layer containing a polylactic acid-based polymer as a main component. For example, a laminate having an outer layer on at least one surface of an inner layer. The inner layer has at least one layer composed of a resin composition mainly containing a polylactic acid-based polymer and an aromatic aliphatic polyester resin, and the outer layer has at least one layer mainly composed of a polylactic acid-based polymer. . Here, the film-like material refers to a sheet or a film. According to the definition in JIS, a sheet is a thin product that is thin and generally has a small thickness instead of length and width. A film is extremely small in thickness compared to length and width, and the maximum thickness is Arbitrarily defined thin flat product, usually supplied in roll form (JIS
K 6900). Therefore, it can be said that a sheet having a particularly small thickness among the sheets is a film. However, since the boundary between the sheet and the film is not clear and it is difficult to clearly distinguish it, in the present application, as described above,
The term "film" is used as a concept that includes both sheets and films.

The polylactic acid-based polymer used in the present invention is a poly (L-lactic acid) having a structural unit of L-lactic acid, a poly (D-lactic acid) having a structural unit of D-lactic acid, and a poly (D-lactic acid) having a structural unit of L-lactic acid. -Poly (DL-lactic acid) which is lactic acid and D-lactic acid or a mixture thereof as a main component. In the present invention, it may be a copolymer with another hydroxycarboxylic acid unit described below, or may contain a small amount of a chain extender residue. The other hydroxycarboxylic acid units copolymerized with polylactic acid include optical isomers of lactic acid (D-lactic acid for L-lactic acid, L-lactic acid for D-lactic acid), glycolic acid, -Hydroxybutyric acid, 4-hydroxybutyric acid,
2-hydroxy-n-butyric acid, 2-hydroxy-3,3-
Dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-
Examples include bifunctional aliphatic hydroxycarboxylic acids such as methyl lactic acid and 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone, and valerolactone.

[0006] The composition of polylactic acid is D-lactic acid: L-lactic acid = 100: 0 to 85:15 or 0: 100 to 15:
It is preferably 85. It is also possible to blend two or more kinds of polylactic acids having different composition ratios of D-lactic acid and L-lactic acid. A polylactic acid-based polymer composed of only D-lactic acid or only L-lactic acid becomes a crystalline resin, has a high melting point, and tends to have excellent heat resistance and mechanical properties. However, when used as a heat-shrinkable film, if the crystallinity is very high, the stretch-oriented crystallization proceeds during stretching, so that it is difficult to adjust the heat shrinkage. On the other hand, DL
-Lactic acid is known to decrease in crystallinity as the proportion of its optical isomer increases. Therefore, when it is used as a heat-shrinkable film, it is preferable to appropriately lower the crystallinity.

As the polymerization method of the polylactic acid polymer, 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 polylactic acid-based polymer having an arbitrary composition. In the ring-opening polymerization method (lactide method), lactide, which is a cyclic dimer of lactic acid, is obtained by using a suitable catalyst and a suitable catalyst to obtain a polylactic acid-based polymer. Can be. In addition, lactide has two L-lactic acids.
There are lactide which is a dimer, D-lactide which is a dimer of D-lactic acid, and DL-lactide which is a dimer of D-lactic acid and L-lactic acid. These may be mixed and polymerized as necessary. Thus, polylactic acid having any composition and crystallinity can be obtained.

[0008] The polylactic acid-based polymer used in the present invention preferably has a weight average molecular weight of 60,000 to 700,000, more preferably 80,000 to 400,000, and particularly preferably 1 to 400,000.
It is between 10,000 and 300,000. If the molecular weight is too small, practical physical properties such as mechanical properties and heat resistance are hardly exhibited, and if it is too large, the melt viscosity is too high and molding processability is poor.

The aromatic aliphatic polyester suitably used in the present invention is a biodegradable aromatic aliphatic polyester comprising an aliphatic dicarboxylic acid component, an aromatic dicarboxylic acid component and an aliphatic diol component. Aliphatic polyesters composed of aliphatic dicarboxylic acids and aliphatic diols are known to have biodegradability,
In order for the aromatic aliphatic polyester to exhibit biodegradability, it is necessary that an aliphatic chain be present between the aromatic rings. Therefore, the aromatic dicarboxylic acid component of the aromatic aliphatic polyester used in the present invention is 50 mol%.
It is preferable to set the following. As the aromatic dicarboxylic acid component, for example, isophthalic acid, terephthalic acid, 2,6
-Naphthalenedicarboxylic acid and the like, examples of the aliphatic dicarboxylic acid component include, for example, succinic acid, adipic acid,
Suberic acid, sebacic acid, dodecane diacid and the like,
Examples of the aliphatic diol include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and the like. The aromatic dicarboxylic acid component, the aliphatic dicarboxylic acid component, or the aliphatic diol component may each use two or more types.
In the present invention, the aromatic dicarboxylic acid component most preferably used is terephthalic acid, the aliphatic dicarboxylic acid component is adipic acid, and the aliphatic diol component is 1,4-
Butanediol.

[0010] The mixing ratio of the polylactic acid-based polymer and the aromatic aliphatic polyester is not particularly limited. However, in the case of a heat-shrinkable label used for PET bottles and bottles, aromatic aliphatic polyester is used. It is preferable that the content of the group III polyester is 50% by mass or less. When the mixing ratio of the aromatic aliphatic polyester exceeds 50% by mass, the film-like material becomes too soft, and the shrink finish is likely to be reduced.

In the present invention, the outer layer has at least one layer mainly composed of a polylactic acid-based polymer. Since the polylactic acid-based polymer and the aromatic aliphatic polyester have different deformation behaviors during stretching, surface roughness tends to occur when a mixture of these resins is stretched, and components other than the polylactic acid-based polymer are contained. The surface roughness increases as the amount increases. Roughness of the surface causes diffusion of the transmitted light, so that the haze increases and the transparency is significantly reduced. Therefore, if surface roughness can be suppressed, diffusion of transmitted light can be suppressed. For example, by providing a transparent layer mainly composed of a polylactic acid-based polymer as an outer layer, surface roughness can be suppressed. In such an outer layer, the content of the polylactic acid-based polymer is 90% by mass or more, preferably 95% by mass or more, and more preferably 100% by mass. If the content of the polylactic acid-based polymer is less than 90% by mass, surface roughness occurs at the time of stretching, and it cannot play a role of preventing diffusion of transmitted light. The polylactic acid-based polymer used for the outer layer may be the same as the polylactic acid-based polymer used for the layer mainly composed of the polylactic acid-based polymer and the aromatic aliphatic polyester constituting the inner layer. However, the present invention is not limited to these. When used as a heat-shrinkable label used for PET bottles and bottle bottles, it is necessary to prevent the bottles from colliding with each other immediately after labeling to prevent holes from being formed by fusing the sheet-like material. It is preferable to use a polylactic acid-based polymer having crystallinity.

In the present invention, a resin composition containing a polylactic acid-based polymer and an aromatic aliphatic polyester as main components includes:
Other biodegradable resins, for example, aliphatic polyesters, polycaprolactones, aliphatic polyester carbonates and the like can be blended within a range not to impair the effects of the present invention. In addition, a heat stabilizer, a light stabilizer, a light absorber, a lubricant, a plasticizer, an inorganic filler, a colorant, a pigment, etc. are added to each layer constituting the heat-shrinkable sheet material in order to adjust various physical properties. You can also.

The layer structure of the heat-shrinkable sheet of the present invention is as follows:
It may be a two-layer laminate of an inner layer and an outer layer or a three-layer laminate of an outer layer / inner layer / outer layer, and is not particularly limited. In these cases, each of the inner layer and the outer layer may be composed of a plurality of layers. Further, the sheet layer product of the present invention is a laminate having a layer mainly composed of a polylactic acid-based polymer and an aromatic polyester as an inner layer, and a layer mainly composed of a polylactic acid-based polymer as an outer layer, Other layers may be provided as long as the effects of the present invention are not impaired. When the outer layer is provided on both surfaces of the inner layer, the outer layers on both surfaces may be layers having the same composition, may be different, and the thicknesses of the layers may be the same or different, From the viewpoints of shrinkage characteristics, curl prevention and the like, it is preferable to provide layers having the same composition and the same thickness on both surfaces. In the present invention, the thickness of the outer layer needs to exceed the height of the unevenness of the surface roughness, and is 1 μm or more, preferably 2 μm or more.

The thickness of the entire heat-shrinkable film is appropriately selected depending on the intended use, and is not particularly limited as long as it can be used for ordinary heat-shrinkable packaging. Specifically, the total thickness is preferably in the range of about 0.01 to 2.0 mm, and more preferably in the range of about 0.01 to 1.5 mm.

As a method for producing a film-like material of the present invention, a resin composition containing a polylactic acid-based polymer and an aromatic polyester as main components and a polylactic acid-based polymer are co-extruded using an extruder. Is generally used, but the method is not limited to these. Specifically, for example, it can be formed by a method in which a polylactic acid-based polymer and an aromatic aliphatic polyester are sufficiently dried and water is removed, and then melt-mixed using an extruder and subjected to coextrusion. For the extrusion, a known method such as a T-die casting method and a tubular method can be employed. However, it is necessary to appropriately set the temperature in consideration of a decrease in molecular weight due to decomposition and the like. The co-extruded film is
After contacting with a rotating casting drum (cooling drum) or being cooled by air, water, etc., it is appropriately heated by hot air, warm water, infrared rays, microwaves, etc. The film is stretched in at least one direction by a roll method of stretching between rolls, a tenter method of extending the gap between the clip rows while gripping a film-like material with a clip using a tenter, a tubular method, or the like. Is preferred.

The stretching temperature and the stretching ratio are appropriately determined according to the mixing ratio of the polylactic acid-based polymer and the aromatic aliphatic polyester, the crystallinity of the polylactic acid-based polymer, and the intended use. The stretching temperature is generally controlled in the range of about 70 to 95 ° C., and the stretching ratio is about 1.5 with respect to the shrinkage direction.
It is appropriately determined within a range of up to 6 times. Also, the uniaxial stretching, biaxial stretching, etc. are appropriately determined according to the application. The stretched film has a heat shrinkage of at least one direction after immersion in hot water of 80 ° C. for 10 seconds.
It is preferably 0% or more.

The heat-shrinkable polylactic acid-based polymer film of the present invention can be used as a packaging material or a shrinkable label material. Containers, foods such as fresh foods, and the like are used as the items to be packaged using the packaging material and the shrinkable label. Examples of the container include a container having high hardness such as a glass bottle, a glass container, and a hard plastic container, or a container formed of paper or a plastic such as polystyrene, polyethylene, or polyethylene terephthalate. These containers are used for any purpose such as food, beverage, and medicine.

[0018]

The present invention will be described in detail with reference to the following examples.
The present invention is not limited by these.
In addition, the measurement value and evaluation in an Example were performed as follows. However, take-up (flow) of film-like material
The direction is described as MD, and the orthogonal direction is described as TD.

Evaluation method: 1) Shrinkage ratio (heat shrinkage ratio) MD was 100 mm and TD was 100 mm.
And cut into a 80 ° C hot water bath.
After immersion for 2 seconds, the dimension between the marked lines was measured, and the heat shrinkage was calculated according to the following equation. However, the heat shrinkage rate is T
The shrinkage in the D direction was measured. Thermal shrinkage (%) = [{(dimension before shrinkage) − (dimension after shrinkage)} / (dimension before shrinkage)] × 100 2) Tensile elongation at break (breaking resistance) According to JIS K7127 A tensile test was performed to measure the elongation of the film-like material, and a substitute evaluation of the rupture resistance was performed. As the test conditions, the elongation of the sheet in the MD direction of the film at an ambient temperature of 23 ° C. was measured at a tensile speed of 200 mm / min. The test was performed five times, and the average value was obtained. A film having a small elongation indicates low rupture resistance, and a film having a large elongation indicates high rupture resistance. 3) Hydroshot (impact resistance) Hydroshot high-speed impact tester HTM-1 type (Co., Ltd.)
(Manufactured by Shimadzu Corporation) was used to measure the impact resistance. 100
A film-like material cut into a size of mm × 100 mm was fixed with a clamp, a weight was dropped at the center of the film-like material to give an impact, and the breaking energy when the film-like material was broken was read. However, the measurement temperature was 23 ° C., and the falling speed of the weight was 3 m / sec. 4) Haze (Transparency) The haze of the sheet was measured according to JIS K7105.

Example 1 A polylactic acid-based polymer having a mixing ratio of L-lactic acid and D-lactic acid of 95.0: 5.0 (trade name “EcoPLA4050” manufactured by Cargill Dow Polymer Co., Ltd.)
D "), 35% by mass of a polylactic acid-based polymer having a mixing ratio of L-lactic acid and D-lactic acid of 90.3: 9.7,
Terephthalic acid 48 mol%, adipic acid 52 mol%, 1,
Each resin of 30% by mass of an aromatic aliphatic polyester composed of 100% by mol of 4-butanediol was dried. Next, these were mixed and mounted on a T-die extruder as an inner layer raw material. Further, L-lactic acid: D-lactic acid = 95.
After drying 100% by mass of a polylactic acid-based polymer having a structure of 0: 5.0, it was mounted on a T-die extruder as an outer layer raw material.
These are melt-extruded at a temperature of 210 ° C. and merged in a die to form a melt having an outer layer / inner layer / outer layer of two or three layers of about 4 μm.
It was quenched by a 3 ° C. casting roll to obtain an unstretched film. Subsequently, the unstretched film material is roll-stretched 1.01 times at 65 ° C. in the longitudinal direction (MD), and then transversely stretched 4 times at 75 ° C. using a tenter in the width direction (TD). A 50 μm heat-shrinkable film was produced. The resulting film was evaluated for heat shrinkage, tensile elongation at break, hydroshot and haze. Table 1 shows the results.

Example 2 In Example 1, 43 mol% of terephthalic acid, 57 mol% of adipic acid and 100 mol% of 1,4-butanediol were used.
A heat-shrinkable film was obtained in the same manner as in Example 1 except that the aromatic aliphatic polyester was changed to 100% by mass. The same evaluation as in Example 1 was performed on the obtained film-like material. Table 1 shows the results.

Comparative Example 1 In Example 1, 50% by mass of a polylactic acid-based polymer having a mixing ratio of L-lactic acid and D-lactic acid of 95.0: 5.0, L-lactic acid and D-lactic acid 50% by mass of a polylactic acid-based polymer having a mixing ratio of 90.3: 9.7 with
Were heat-shrinkable in the same manner as in Example 1 except that each resin was dried and melt-mixed with a T-die extruder to form a single-layer melt. The same evaluation as in Example 1 was performed on the obtained film-like material. Table 1 shows the results.

Comparative Example 2 In Example 1, 35% by mass of a polylactic acid-based polymer having a mixing ratio of L-lactic acid and D-lactic acid of 95.0: 5.0, L-lactic acid and D-lactic acid 350.3% by mass of a polylactic acid-based polymer having a mixing ratio of 90.3: 9.7 with terephthalic acid, 52% by mol of adipic acid,
Except that a resin obtained by drying and mixing each resin of 30% by mass of an aromatic aliphatic polyester composed of 100 mol% of 1,4-butanediol was melt-mixed with a T-die extruder to form a single-layer melt. A heat-shrinkable film was obtained in the same manner as in Example 1. The same evaluation as in Example 1 was performed on the obtained film-like material. Table 1 shows the results.

[0024]

[Table 1]

As is evident from Table 1, it was found that Examples 1 and 2 were excellent in all of rupture resistance, impact resistance and transparency. That is, according to the present invention, even with a substantially uniaxially stretched film-like material, good results can be obtained with respect to instantaneous impact. On the other hand, the film-like material of Comparative Example 1 having a single-layer structure of the polylactic acid-based polymer had low values in both the breaking resistance and the impact resistance, and the single-layer structure of the resin in which the polylactic acid-based polymer and the aliphatic polyester were blended. It was found that the film-like material of Comparative Example 2 was extremely poor in transparency. The good impact resistance is a level at which a broken film after punching by hydroshot does not tear in the stretching direction, and the numerical value is 10 kgf · mm or more.

[0026]

As described above in detail, according to the present invention, a heat-shrinkable film having biodegradability and excellent in all of rupture resistance, impact resistance and transparency is provided. be able to.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F100 AK41A AK41B AK41C AL05B BA03 BA06 EH20 EJ37 EJ38 GB15 GB90 JA03 JK10 JL00 JN01 YY00B

Claims (5)

[Claims] 1. A laminate comprising a layer composed of a resin composition mainly composed of a polylactic acid-based polymer and an aromatic aliphatic polyester resin and a layer mainly composed of a polylactic acid-based polymer. Heat shrinkable film. 2. A laminate comprising a resin composition comprising a polylactic acid-based polymer and an aromatic aliphatic polyester resin as a main component and a layer comprising a polylactic acid-based polymer as a main component is stretched in at least one direction. A heat-shrinkable film-like material characterized by being subjected to: 3. An inner layer having at least one layer made of a resin composition mainly containing a polylactic acid-based polymer and an aromatic aliphatic polyester resin, and an outer layer mainly containing a polylactic acid-based polymer as an outer layer. A heat-shrinkable film-like product obtained by stretching a laminate having at least one layer in at least one direction. 4. The aromatic aliphatic polyester resin,
The heat-shrinkable film according to any one of claims 1 to 3, comprising an aliphatic dicarboxylic acid component, an aromatic dicarboxylic acid component, and an aliphatic diol component. 5. The aromatic aliphatic polyester resin,
The heat-shrinkable film according to any one of claims 1 to 4, further comprising an aromatic dicarboxylic acid component in a range of 50 mol% or less.