JP3664969B2 - Heat-shrinkable polylactic acid polymer film - Google Patents

Description

【００２４】
表１から明らかなように、実施例１〜３は耐破断性および耐衝撃性ともに優れていることが分かった。すなわち、本発明によれば実質一軸延伸フィルム状物でも、瞬間的な衝撃に対して良好な結果が得られることが分かった。
一方、ポリ乳酸系重合体のみからなる比較例１のフィルム状物は耐破断性および耐衝撃性ともに低い値となり、ポリ乳酸系重合体と脂肪族ポリエステルとをブレンドした比較例２のフィルム状物は、引張試験等の低速での破断性は良好であったが瞬間的な衝撃に対しては弱いことが分かった。
なお、良好な耐衝撃性は、ハイドロショットでの打ち抜き後の破断フィルム状物が延伸方向に裂けないレベルであり、数値では１０ｋｇｆ・ｍｍ以上である。
【００２５】
【発明の効果】
以上、詳しく説明したように、本発明によれば、生分解性があり、かつ耐破断性および耐衝撃性に優れた熱収縮性ポリ乳酸系重合体フィルム状物を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat-shrinkable film-like material comprising a polylactic acid-based polymer as a main component, and particularly suitable for shrink-wrapping, shrink-bound packaging, shrink-labeling, etc. It relates to a united film.
[0002]
[Prior art and problems to be solved by the invention]
Heat-shrinkable films used for shrink wrap, shrink-bound wrap, shrink labels, etc. are known to mainly contain polyvinyl chloride (PVC), styrene-butadiene block copolymer (SBS), polyester resin, and the like. ing. Although these are widely used, when discarded after use, they are chemically stable and non-biodegradable, so they remain and accumulate almost without being decomposed. As a result, the capacity of the waste disposal site is saturated in a short period of time.
Therefore, biodegradable materials that have low combustion heat and are safe for the human body and the like have been demanded, and many studies have been conducted. As one of them, polylactic acid is known. Polylactic acid has a calorific value less than half that of polyethylene, and is naturally hydrolyzed in soil and water, and then becomes a harmless decomposition product by microorganisms. Japanese Patent Application Laid-Open No. 5-221790 discloses a heat-shrinkable film made of polylactic acid. However, since the shrinkage temperature is as high as 140 to 150 ° C., it can be used only for special purposes.
Originally, polylactic acid films and sheets are brittle and inferior in impact resistance due to the inherent brittleness of the material, and are therefore difficult to put into practical use. In particular, when a shrinkable film is formed by uniaxial stretching, the brittleness in the non-stretching direction is not improved. In order to improve this, a method of blending aliphatic polyester is known. According to such a method, although a good result is obtained in the breaking property (breaking resistance) at a low speed such as a tensile test, it is weak against an instantaneous impact (impact resistance) and is torn. There was a problem.
Therefore, there has been a demand for a heat-shrinkable polylactic acid-based film excellent in impact resistance in a substantially uniaxially stretched film mainly composed of polylactic acid.
[0003]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.
That is, the heat-shrinkable polylactic acid polymer film-like material of the present invention is a film obtained by stretching a film- like material composed of a polylactic acid-based polymer and an aromatic aliphatic polyester resin as main components in at least one direction. The heat-shrinkage rate after being immersed in warm water at 80 ° C. for 10 seconds is 10% or more in at least one direction, and the hydroshot value is 10 kgf · mm or more .
Here, the aromatic aliphatic polyester resin may include an aliphatic dicarboxylic acid component, an aromatic dicarboxylic acid component, and an aliphatic diol component.
The aromatic aliphatic polyester resin may contain an aromatic dicarboxylic acid component in a range of 50 mol% or less.
[0004]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The heat-shrinkable polylactic acid-based polymer film-like product of the present invention comprises a resin composition containing a polylactic acid-based polymer and an aromatic aliphatic polyester resin as main components.
Here, the film-like material means a sheet or a film. According to the definition in JIS, a sheet is a thin, generally flat product whose thickness is small compared to the length and width, and a film is extremely small compared to the length and width and has a maximum thickness. An arbitrarily limited thin flat product, usually supplied in the form of a roll (JIS K 6900). Therefore, it can be said that a particularly thin sheet is a film. However, since the boundary between the sheet and the film is not clear and it is difficult to distinguish clearly, in the present application, as described above, the term “film-like product” is used as a concept including both the sheet and the film. use.
[0005]
The polylactic acid-based polymer used in the present invention includes poly (L-lactic acid) having a structural unit of L-lactic acid, poly (D-lactic acid) having a structural unit of D-lactic acid, a structural unit of L-lactic acid, and The main component is poly (DL-lactic acid) which is D-lactic acid or a mixture thereof. In the present invention, it may be a copolymer with other hydroxycarboxylic acid units described later, or may contain a small amount of a chain extender residue.
Examples of 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, 3 2-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, 2-hydroxycaproic acid, etc. Examples thereof include lactones such as functional aliphatic hydroxycarboxylic acids, caprolactone, butyrolactone, and valerolactone.
[0006]
The polylactic acid is preferably D-lactic acid: L-lactic acid = 100: 0 to 85:15 or 0: 100 to 15:85. It is also possible to blend two or more types of polylactic acid having different constituent ratios of D-lactic acid and L-lactic acid.
A polylactic acid polymer containing only D-lactic acid or L-lactic acid is a crystalline resin, has a high melting point, and tends to be excellent in heat resistance and mechanical properties. However, when used as a heat-shrinkable film-like material, if the crystallinity is very high, stretching and orientation crystallization proceeds at the time of stretching, so that it is difficult to adjust the heat shrinkage rate. On the other hand, it is known that the crystallinity of DL-lactic acid decreases as the proportion of the optical isomer increases. Therefore, when used as a heat-shrinkable film-like product, it is preferable to moderately reduce the crystallinity.
[0007]
As a polymerization method for 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, a polylactic acid polymer having an arbitrary composition can be obtained by directly dehydrating condensation polymerization of L-lactic acid, D-lactic acid, or a mixture thereof.
In addition, in the ring-opening polymerization method (lactide method), a lactate which is a cyclic dimer of lactic acid is obtained by using a suitable catalyst while using a polymerization regulator or the like as necessary. Can do. In addition, the lactide includes lactide which is a dimer of L-lactic acid, 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. Can be mixed and polymerized as necessary to obtain polylactic acid having an arbitrary composition and crystallinity.
[0008]
The polylactic acid 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 100,000 to 300,000. If the molecular weight is too small, practical physical properties such as mechanical properties and heat resistance are hardly expressed, and if it is too large, the melt viscosity is too high and the molding processability is poor.
[0009]
The aromatic aliphatic polyester preferably used in the present invention is a biodegradable aromatic 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, but in order to develop biodegradability in aromatic polyesters, aliphatic chains are not between aromatic rings. It is necessary to exist. For this reason, the aromatic dicarboxylic acid component of the aromatic aliphatic polyester used in the present invention is preferably 50 mol% or less.
Examples of the aromatic dicarboxylic acid component include isophthalic acid, terephthalic acid, and 2,6-naphthalenedicarboxylic acid. Examples of the aliphatic dicarboxylic acid component include succinic acid, adipic acid, suberic acid, sebacic acid, Examples include dodecanedioic acid, and examples of the aliphatic diol include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and the like. Two or more types of aromatic dicarboxylic acid components, aliphatic dicarboxylic acid components, or aliphatic diol components can be used.
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 polymer and the aromatic aliphatic polyester is not particularly limited, but in the case of a heat-shrinkable label used for PET bottles and bottle bottles, the aromatic aliphatic polyester is It is preferable that it is 50 weight% or less. If the mixing ratio of the aromatic aliphatic polyester exceeds 50% by weight, the film-like product becomes too soft and the shrinkage finish property tends to be lowered.
[0011]
In the present invention, other biodegradable resins, for example, aliphatic polyester, polycaprolactone, aliphatic polyester carbonate, etc. are blended within the range that does not impair the properties of the heat-shrinkable polylactic acid polymer film. Can do.
In addition, for the purpose of adjusting various physical properties, a heat stabilizer, a light stabilizer, a light absorber, a lubricant, a plasticizer, an inorganic filler, a colorant, a pigment, and the like can be added.
[0012]
The thickness of the film-like material is appropriately selected depending on the application, and is not particularly limited as long as it is a thickness that can be used for ordinary heat shrink wrapping or the like. Specifically, the total thickness is about 0.01 to 2. It is preferably in the range of 0 mm, more preferably in the range of about 0.01 to 1.5 mm.
[0013]
As a method for producing the film-like product of the present invention, a method in which a polylactic acid polymer and an aromatic aliphatic polyester are sufficiently dried to remove moisture, and then melt mixed using an extruder and extruded is generally used. However, it is not limited to these. For the extrusion, a known method such as a T-die casting method or 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.
The melt-extruded film-like material is brought into contact with a rotating casting drum (cooling drum) or cooled with air, water, etc., and then appropriately heated with hot air, hot water, infrared rays, microwaves, etc. By a roll method that stretches an object between two rolls with a difference in peripheral speed, a tenter method that stretches a row of clip rows while holding a film-like object with a clip using a tenter, a tubular method, etc. , Stretched in at least one direction.
[0014]
The stretching temperature and stretching ratio are appropriately determined depending on the mixing ratio of the polylactic acid polymer and the aromatic aliphatic polyester, the crystallinity of the polylactic acid polymer, etc., and the application to be applied. The temperature is controlled in the range of about 70 to 95 ° C., and the draw ratio is appropriately determined in the range of about 1.5 to 6 times with respect to the shrinking direction. Further, uniaxial stretching, biaxial stretching, and the like are also appropriately determined according to the application.
In addition, it is preferable that the film-like thing after extending | stretching is 10% or more in a heat shrink rate at least in one direction after being immersed in 80 degreeC warm water for 10 second.
[0015]
The heat-shrinkable polylactic acid polymer film-like product of the present invention can be used as a packaging material or a shrinkable label material. Examples of the objects to be packaged in which the packaging material and the shrinkage label are used include containers, foods such as fresh foods, and the like. 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 from paper, plastic such as polystyrene, polyethylene, and polyethylene terephthalate. These containers are used for arbitrary uses such as foods, beverages, and medicines.
[0016]
【Example】
The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
In addition, the measured value and evaluation in an Example were performed as follows. However, the take-up (flow) direction of the film-like material is described as MD, and its orthogonal direction is described as TD.
[0017]
Evaluation methods:
1) Cut the film with a heat shrinkage rate so that the MD is 100 mm and the TD is 100 mm, immerse in a hot water bath at 80 ° C. for 10 seconds, measure the dimension between the marked lines, The heat shrinkage rate was calculated according to However, the thermal shrinkage was measured by shrinkage in the TD direction.
Thermal shrinkage rate (%) = [{(dimension before shrinkage) − (dimension after shrinkage)} / (dimension before shrinkage)] × 100
2) Tensile elongation at break (breaking resistance)
In accordance with JIS K7127, a tensile test was performed, the elongation of the film-like material was measured, and substitute evaluation of the fracture resistance was performed. As test conditions, the elongation of the sheet in the MD direction of the film-like material at an atmospheric temperature of 23 ° C. at a tensile speed of 200 mm / min was measured. In addition, the test was performed 5 times and the average value was calculated | required. A film-like product having a small elongation has low fracture resistance, and a film having a large elongation has high fracture resistance.
3) Hydroshot (impact resistance)
Impact resistance was measured using a hydroshot high-speed impact tester HTM-1 type (manufactured by Shimadzu Corporation). A film-like material cut out to a size of 100 mm × 100 mm was fixed with a clamp, a weight was dropped on 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 is 23 ° C. and the falling speed of the weight is 3 m / sec.
[0018]
(Example 1)
35% by weight of a polylactic acid polymer (trade name “EcoPLA4050D” manufactured by Cargill Dow Polymer Co., Ltd.) having a mixing ratio of L-lactic acid and D-lactic acid of 95.0: 5.0, L-lactic acid and D-lactic acid Is a polylactic acid polymer (trade name “EcoPLA4060D” manufactured by Cargill Dow Polymer Co., Ltd.) having a mixing ratio of 90.3: 9.7, 35 wt%, terephthalic acid 48 mol%, adipic acid 52 mol%, 1, Each resin of 30% by weight of aromatic aliphatic polyester (trade name “Ecoflex”, manufactured by BASF Corp.) consisting of 100 mol% of 4-butanediol was dried. Subsequently, these were mixed and mounted on a T-die extruder, melt extruded at a temperature of 210 ° C., and the melt was quenched with a casting roll at about 43 ° C. to obtain an unstretched film. Subsequently, the unstretched film-like material was 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 obtained film-like product was evaluated for heat shrinkage, tensile elongation at break and hydroshot. The results are shown in Table 1.
[0019]
(Example 2)
In Example 1, 40% by weight of a polylactic acid polymer having a mixing ratio of L-lactic acid and D-lactic acid of 95.0: 5.0 (trade name “EcoPLA4050D” manufactured by Cargill Dow Polymer Co., Ltd.), L- 40% by weight of polylactic acid polymer (trade name “EcoPLA4060D” manufactured by Cargill Dow Polymer Co., Ltd.) having a mixing ratio of lactic acid and D-lactic acid of 90.3: 9.7, terephthalic acid 43 mol%, adipic acid 57 Example 1 except that 20% by weight of each aliphatic aliphatic polyester (trade name “East Bond 14766”, manufactured by Eastman Chemical Co.) consisting of 100% by mole of 1,4-butanediol was used. A heat-shrinkable film was obtained.
About the obtained film-form thing, evaluation similar to Example 1 was performed. The results are shown in Table 1.
[0020]
(Example 3)
In Example 1, 35% by weight of a polylactic acid polymer having a mixing ratio of L-lactic acid and D-lactic acid of 95.0: 5.0 (trade name “EcoPLA4050D” manufactured by Cargill Dow Polymer Co., Ltd.), L- 35% by weight of polylactic acid polymer (trade name “EcoPLA4060D” manufactured by Cargill Dow Polymer Co., Ltd.) having a mixing ratio of lactic acid and D-lactic acid of 90.3: 9.7, terephthalic acid 48 mol%, adipic acid 52 20% by weight of an aromatic aliphatic polyester (trade name “Ecoflex” manufactured by BASF Corporation) consisting of 100% by mole of 1,4-butanediol, polybutylene succinate / adipate which is an aliphatic polyester (Showa Polymer Co., Ltd.) Manufactured under the trade name “Bionore # 3003”) 10% by weight of each resin was used in the same manner as in Example 1 except that each resin was dried and used. To obtain things.
About the obtained film-form thing, evaluation similar to Example 1 was performed. The results are shown in Table 1.
[0021]
(Comparative Example 1)
In Example 1, 50% by weight of a polylactic acid polymer (trade name “EcoPLA4050D” manufactured by Cargill Dow Polymer Co., Ltd.) having a mixing ratio of L-lactic acid and D-lactic acid of 95.0: 5.0, L- A polylactic acid polymer having a mixing ratio of lactic acid and D-lactic acid of 90.3: 9.7 (manufactured by Cargill Dow Polymer Co., Ltd., trade name “EcoPLA4060D”) was used by drying 50% by weight of each resin. Except for this, a heat-shrinkable film was obtained in the same manner as in Example 1.
About the obtained film-form thing, evaluation similar to Example 1 was performed. The results are shown in Table 1.
[0022]
(Comparative Example 2)
In Example 1, 35% by weight of a polylactic acid polymer having a mixing ratio of L-lactic acid and D-lactic acid of 95.0: 5.0 (trade name “EcoPLA4050D” manufactured by Cargill Dow Polymer Co., Ltd.), L- Polybutylene succinate which is 35% by weight of polylactic acid polymer (trade name “EcoPLA4060D” manufactured by Cargill Dow Polymer Co., Ltd.) having a mixing ratio of lactic acid and D-lactic acid of 90.3: 9.7, aliphatic polyester / Adipate (made by Showa Polymer Co., Ltd., trade name “Bionore # 3003”) A film-like product was obtained in the same manner as in Example 1 except that each resin was dried and used. About the obtained film-form thing, evaluation similar to Example 1 was performed. The results are shown in Table 1.
[0023]
[Table 1]

[0024]
As is apparent from Table 1, Examples 1 to 3 were found to be excellent in both fracture resistance and impact resistance. That is, according to the present invention, it has been found that even a substantially uniaxially stretched film-like product can obtain a good result against an instantaneous impact.
On the other hand, the film-like product of Comparative Example 1 consisting only of a polylactic acid polymer has low values for both fracture resistance and impact resistance, and the film-like product of Comparative Example 2 blended with a polylactic acid polymer and an aliphatic polyester. It was found that the breaking property at a low speed such as a tensile test was good, but it was weak against an instantaneous impact.
In addition, good impact resistance is a level at which a ruptured film-like product after being punched by hydroshot does not tear in the stretching direction, and is numerically 10 kgf · mm or more.
[0025]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide a heat-shrinkable polylactic acid-based polymer film that is biodegradable and excellent in fracture resistance and impact resistance.

Claims (3)

A film-like product made of a resin composition composed mainly of a polylactic acid-based polymer and an aromatic aliphatic polyester resin, which is stretched in at least one direction, and is immersed in warm water at 80 ° C. for 10 seconds. A heat-shrinkable polylactic acid polymer film-like product having a heat shrinkage ratio of 10% or more in at least one direction and a hydroshot value of 10 kgf · mm or more .   The heat-shrinkable polylactic acid-based polymer film according to claim 1, wherein the aromatic aliphatic polyester resin comprises an aliphatic dicarboxylic acid component, an aromatic dicarboxylic acid component, and an aliphatic diol component.   The heat-shrinkable polylactic acid-based polymer according to claim 1, wherein the aromatic aliphatic polyester resin contains an aromatic dicarboxylic acid component in a range of 50 mol% or less. Film-like product.