JPH1142752A - Biodegradable laminated film having good gas barrier property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable sheet which is excellent in transparency and gas barrier properties effective as a general packaging material. SOLUTION: A biodegradable laminated film has a vapor deposition layer of an oxide laminated at least on one side of a resin layer containing an aliphatic polyester having a main repeating unit of the general formula-O-CHR-CO- (wherein R represents H and l-3C alkyl radicals), satisfying the conditions of (1) a haze value of at most 5 %, (2) a water-vapor permeability of at most 20 g/m<2> .24 hr (40 deg.C/90% RH), and (3) an oxygen permeability of at most 100 cc/m<2> .24 hr.atm (25 deg.C/50% RH).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable laminated film having excellent gas barrier properties, particularly, fresh food, processed food,
The present invention relates to a biodegradable laminated film excellent in transparency and gas barrier properties, which are important requirements for packaging films for pharmaceuticals, medical devices, electronic components, and the like.

[0002]

2. Description of the Related Art Conventionally, various plastics such as polyolefins represented by polyethylene, polypropylene, polyethylene terephthalate nylon 6 and the like, aromatic polyesters and polyamides have been used for films for packaging various products including foods. These packaging films are to be collected after use and disposed of by incineration or burying in soil. However, it takes a lot of effort to recover it,
It is well known that it is actually left uncollected and causes various problems such as environmental pollution. In addition, in the case of incineration, the thermal power is too strong, the furnace is severely damaged, and a large amount of fuel is required, which increases the cost. on the other hand,
When buried in the soil, there is a problem that the waste does not have biodegradability and remains semipermanently in the soil. Under these circumstances, there has been an increasing demand for various packaging films having good biodegradability.

[0003] Therefore, in order to impart biodegradability to the above polyethylene and the like, various studies have been made on blending a biodegradable component such as starch. Furthermore, a method of imparting photodegradability or a method of blending a biodegradable component of starch with photodegradable polyethylene and the like have been studied, and are attracting attention as a solution to the above-mentioned problem. However, in these methods, the starch component is biodegradable and thus decomposed by microorganisms in the soil.
The polymer parts other than the starch are not degraded, and ultimately do not provide a fundamental solution to the above problem.

[0004] From these facts, along with the increasing public awareness of environmental protection in recent years, when plastic processed products are generally disposed of in the natural environment, they are decomposed and disappear over time, adversely affecting the natural environment. There was a need for plastic products that did not affect it.

As a solution to the above problem, various biodegradable polymer materials in which the polymer itself has biodegradability have been studied. Among them, polylactic acid is conventionally widely known as a hydrolysable polymer, and is used as a molded product for medical use (Japanese Patent Publication No. 41-2734, Japanese Patent Publication No. 63-68155, etc.). Various applications have been studied as basic raw materials for biodegradable general-purpose materials.

Above all, a biaxially stretched film using a polylactic acid-based polymer has excellent mechanical properties equivalent to a general-purpose film, and is therefore expected to be applied to a wide range of uses including general packaging materials. However, when used as a food packaging material, a significant disadvantage of this film is that it has a relatively high gas permeability and shortens the shelf life of food packaged with such materials. Therefore, Table 8-8
Japanese Patent No. 05825 discloses a solution to this problem, in which a metal such as aluminum is laminated as a vapor-deposited film on the surface thereof. However, a film obtained by this method is required as a characteristic particularly required for food packaging. At present, there is no essential solution because of the loss of transparency and limited applications.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional biodegradable films or biodegradable laminated films, and has excellent transparency and gas barrier properties effective as general packaging materials. It is intended to provide a biodegradable film.

[0008]

In order to achieve the above object, the biodegradable laminated film having excellent gas barrier properties of the present invention has a main repeating unit represented by the general formula -O-CHR-CO-.
(R represents H or an alkyl group having 1 to 3 carbon atoms.) A resin layer containing an aliphatic polyester as a main component has an oxide deposited layer laminated on at least one surface of the resin layer. ) To (3) are satisfied. (1) Haze value ≦ 5% (2) Moisture permeability ≦ 20 g / m ² · 24 hr (40 ° C./90
% RH) (3) Oxygen permeability ≦ 100 cc / m ² · 24 hr · at
m (25 ° C / 50% RH)

The biodegradable laminated film having excellent gas barrier properties of the present invention having the above constitution has excellent transparency and gas barrier properties to the extent that it is effective as a general packaging material, and has excellent biodegradability. Having.

In a preferred embodiment of the present invention, the thickness of the resin layer containing an aliphatic polyester as a main component is 10 to 25.
0 μm, and the thickness of the deposited oxide layer is 10 to 5000
Å could be.

[0011] In a preferred embodiment of the present invention,
The aliphatic polyester can be polylactic acid.

Further, as a preferred embodiment of the present invention, the oxide can be silicon oxide and / or aluminum oxide.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a biodegradable laminated film having excellent gas barrier properties according to the present invention will be described.

The main repeating unit used in the present invention has the general formula -O-CHR-CO- (R is H or carbon
And represents an alkyl group of 1 to 3. Examples of the aliphatic polyester include, but are not limited to, polylactic acid, polyglycolic acid, and poly (2-oxybutyric acid). In addition to these homopolymers, mixtures and copolymers can also be used. Those having an asymmetric carbon in the constituent carbon atoms of the aliphatic polyester are L-
There are optical isomers such as a isomer, a DL-isomer, and a D-isomer, and any of them may be used, or a mixture of these isomers may be used. The above-mentioned aliphatic polyester used as a material of the biodegradable laminated film of the present invention is produced by a known method such as ring-opening polymerization of a corresponding dehydrated cyclic ester compound of α-oxyacid.

The biodegradable aliphatic polyester has a viscosity average molecular weight of usually 5,000 to 500,000.
When the viscosity average molecular weight is less than 5,000, the physical properties of the obtained biodegradable laminated film are inferior and the biodegradation rate tends to be too high, which is not preferable for achieving the object of the present invention. Further, the viscosity average molecular weight is preferably 10,000 or more in order to sufficiently ensure the extrudability from a film-forming machine during the production of a biodegradable laminated film and the stretchability with a biaxial stretching machine. On the other hand, a high viscosity polymer having a viscosity average molecular weight exceeding 500,000 has a problem that melt extrusion becomes difficult. For these reasons, a particularly preferred range of the viscosity average molecular weight is 50,000 to 300,000.

Known additives can be added to the biodegradable aliphatic polyester as required. For example, a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a lightfast agent, an impact resistance improver, and the like may be contained. For example, anionic surfactants such as potassium lauryl phosphate, cationic surfactants such as quaternary ammonium salts, ethylene oxide addition of aliphatic higher alcohols and higher fatty acids, taking into account antistatic properties as required. Nonionic surfactants such as products, polyalkylene glycols such as polyethylene glycol, polyethylene glycol / polypropylene glycol block copolymers, and silicone oils such as dimethyl polysiloxane, polyether-modified silicone oil, and higher alkoxy-modified silicone oil. Alternatively, two or more kinds can be contained. Further, the biodegradable aliphatic polyester used in the present invention includes polymers such as polyamino acids, talc, calcium carbonate, calcium sulfate,
One or more kinds of inorganic substances such as calcium chloride, starch, protein, food additives, and the like can be appropriately mixed, and the mechanical properties, biodegradation properties, and the like can be variously changed.
However, the biodegradable aliphatic polyester film of the present invention has a high transparency even before the vapor deposition layer is deposited, since after the oxide vapor deposition layer is vapor-deposited, it is necessary to see the contents in a transparent manner. Therefore, it is necessary to consider the type of additive.

The biodegradable aliphatic polyester film, which is a resin layer containing an aliphatic polyester as a main component, which constitutes the present invention, can be obtained by film-forming and stretching by a known method.
It is preferable that the film is heat-set after biaxial stretching. For example, when the biodegradable aliphatic polyester film used in the present invention is manufactured by an extrusion molding method, a known T-die method, inflation method and the like can be applied, and an unstretched film can be obtained by these methods. The extrusion temperature ranges from the melting temperature (Tm) of the biodegradable aliphatic polyester to be used to Tm + 70 ° C.,
m + 20 to Tm + 50 ° C. If the extrusion temperature is too low, extrusion stability is difficult to obtain, and overloading is liable to occur. Conversely, if the content is too high, the decomposition of the biodegradable aliphatic polyester becomes severe, which is not preferable. As the die of the extruder used for producing the biodegradable aliphatic polyester film constituting the present invention, a die having an annular or linear slit can be used. The temperature of the die is about the same as the extrusion temperature range. The draw ratio (ratio of T die lip interval / film thickness) when extruding with a T-die is 5
~ 130 is preferred.

The biaxial stretching of the unstretched film made of the biodegradable aliphatic polyester may be carried out either sequentially or simultaneously with the first and second axes. The stretching temperature is
Tg (glass transition point) to T of the aliphatic polyester used
The range of g + 50 ° C. is preferred. More preferably, Tg +
The range is 10 to Tg + 40 ° C. If the stretching temperature is lower than Tg, stretching is difficult, and if it exceeds Tg + 50 ° C., the thickness uniformity and the mechanical strength of the obtained film are undesirably reduced.

The stretching in the longitudinal and transverse directions may be performed in one step or in multiple steps, but it is ultimately at least 3 times, more preferably 3.5 times or more in each stretching direction. -9 times or more in horizontal area magnification, more preferably 1
Stretching by a factor of two or more is a general condition in terms of thickness uniformity and mechanical properties. When the longitudinal and transverse stretching ratios are 3 times or less, respectively, and the area ratio is 9 times or less, it is difficult to obtain a film with good thickness uniformity, and the improvement in physical properties such as mechanical strength is also poor. The thickness of the resin layer containing an aliphatic polyester as a main component is generally about 10 to 250 μm, and preferably about 12 to 250 μm.

The biodegradable aliphatic polyester film constituting the present invention may be multi-layered by a coextrusion method or a coating method with another resin in the production process. In addition, the biodegradable aliphatic polyester film constituting the present invention may be subjected to corona discharge treatment, coating treatment, or flame treatment in order to improve adhesion and wettability depending on the use. In particular, before laminating an oxide vapor-deposited layer on the above-mentioned film, the above-mentioned treatment can be performed in advance in order to increase the adhesion between the film and the oxide vapor-deposited layer.

The oxide deposited layer constituting the present invention may be any oxide deposited layer exhibiting transparency and gas barrier properties satisfying the above conditions (1) to (3). A non-metal oxide is widely used, and a vapor deposition layer containing silicon oxide and / or aluminum oxide as a main component is particularly preferable.
The deposited layers of these oxides are suitable because no harmful substances are produced even if they are discarded after use.

The thickness of the deposited layer of the oxide is usually 10 to 50.
00 °, more preferably in the range of 50-2000 °. If the film thickness is less than 10 mm, it is difficult to obtain sufficient gas barrier properties, and even if the film thickness exceeds 5,000 mm, the effect of improving gas barrier properties is saturated, bending resistance becomes poor, and manufacturing costs are reduced. It is not practical to go up.

For the formation of the oxide deposited layer, a physical vapor deposition method such as a vacuum vapor deposition method, a sputtering method or an ion plate method, or a chemical vapor deposition method such as a CVD method is appropriately used.
As the heating method employed at this time, resistance heating, induction heating, electron beam heating, or the like can be appropriately employed. Oxygen, nitrogen, hydrogen, argon, carbon dioxide, water vapor, or the like may be introduced as a reaction gas, or a reactive deposition method using a method such as ozone addition or ion assist may be employed, and a bias may be applied to the substrate. It is also possible to change the film forming conditions such as heating and cooling of the substrate. Such deposition materials, reaction gas, substrate bias, and heating / cooling conditions can be similarly changed when employing the sputtering method or the CDV method. Before or during the deposition of the oxide, the surface of the substrate to be deposited is subjected to a corona discharge treatment, a flame treatment, a low-temperature plasma treatment, a glow discharge treatment, a reverse sputtering treatment, a surface treatment, etc. to increase the adhesion strength of the oxide. It is also effective to raise it further.

The biodegradable aliphatic polyester film according to the present invention, on which the oxide deposited layer is laminated, is colorless and transparent,
The haze (haze value) of the biodegradable laminated film needs to be 5% or less because the packaged contents must be visible. It should be noted that other layers may be formed at all without impairing the object of the present invention.

[0025]

EXAMPLES Hereinafter, the contents and effects of the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to the following examples unless departing from the gist thereof. The methods for evaluating physical properties in the following examples and comparative examples are as follows.

(Haze value) The haze value was measured using a haze meter manufactured by Nippon Denshoku Co., Ltd. according to JIS-K6714.

(Gas barrier property) The amount of oxygen permeation is measured by an oxygen permeability measuring device (“OX-TRAN 10 / 50A”) Mod.
The measured value was 0% humidity, 25 ° C. temperature, and purged for 2 days. The water vapor transmission rate was measured using a water vapor transmission rate measuring device (“PERMATRAN” M).
Oder Controls) at a temperature of 40
The measurement was performed by purging at 90 ° C. and a humidity of 90% for 2 days.

(Impact strength) Measured at 23 ° C. using a film impact tester (manufactured by Toyo Seiki Co., Ltd.).

(Aging) As one of the biodegradability indicators,
Fill the sampled soil with a film and keep the temperature 3
After maintaining at 5 ° C. for 6 months, changes in the appearance of the film were observed. The evaluation rank is as follows. ：: noticeable change from appearance ×: no change in appearance

Example 1 Using a poly-L-lactic acid having a viscosity-average molecular weight of 250,000 as a raw material, using a 30 mm diameter extruder with a T-die, melt-extruding at a resin temperature of 210 ° C., cooling with a chill roll, Immediately after obtaining an unstretched film of about 300 μm in lengthwise direction at 75 ° C. with a roll-type stretching machine.
It is stretched twice, and is further stretched at 100 ° C. in the transverse direction using a tenter-type stretching machine.
And stretched 4 times. Next, after heat-setting at 150 ° C. while relaxing by 6%, a corona discharge treatment was performed to obtain a stretched film having a thickness of 25 μm. The obtained corona discharge treated 2
Using an electron beam heating type vacuum evaporation apparatus, an evaporation layer having a thickness of 200 ° and an aluminum oxide content of 40% by weight was laminated on the axially stretched film using silicon dioxide and aluminum oxide as evaporation materials. Table 1 shows the physical properties.

Example 2 A biaxially stretched film and a laminated film having a vapor deposited layer were prepared in the same manner as in Example 1 except that poly-DL-lactic acid having a viscosity average molecular weight of 350,000 was used as a raw material. . Table 1 shows the physical properties.

(Example 3) Polyglycolic acid having a viscosity average molecular weight of 280,000 was melt-extruded at 270 ° C, and the longitudinal and transverse stretching temperatures were changed to 95 ° C and 110 ° C, respectively, and the heat setting temperature was changed to 200 ° C. Except for this, a biaxially stretched film was obtained by the method described in Example 1, and then a film having a vapor deposited layer laminated thereon was obtained. Table 1 shows the physical properties.

(Comparative Example 1) A laminated film having a metal deposition layer made of 100% aluminum was obtained on the biaxially stretched film made of the raw materials described in Example 1. Table 1 shows the physical properties
Pointing out toungue

[0034]

[Table 1]

[0035]

According to the biodegradable laminated film of the present invention having excellent gas barrier properties, it has excellent biodegradability while having both transparency and gas barrier properties, and is extremely useful as an environmentally friendly general packaging film. It is.

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Hideaki Ishihara 2-1-1 Katada, Otsu-shi, Shiga Prefecture Toyobo Co., Ltd. Research Laboratory

Claims (4)

[Claims] (1) a main repeating unit represented by the general formula -O-CH
An oxide vapor-deposited layer is laminated on at least one surface of a resin layer mainly containing an aliphatic polyester which is R-CO- (R represents H or an alkyl group having 1 to 3 carbon atoms), A biodegradable laminated film having excellent gas barrier properties, satisfying the following conditions (1) to (3). (1) Haze value ≦ 5% (2) Moisture permeability ≦ 20 g / m ² · 24 hr (40 ° C./90
% RH) (3) Oxygen permeability ≦ 100 cc / m ² · 24 hr · at
m (25 ° C / 50% RH) 2. The gas according to claim 1, wherein the thickness of the resin layer containing an aliphatic polyester as a main component is 10 to 250 μm, and the thickness of the oxide deposition layer is 10 to 5000 °. Biodegradable laminated film with excellent barrier properties. 3. The biodegradable laminated film excellent in gas barrier properties according to claim 1, wherein the aliphatic polyester is polylactic acid. 4. The method according to claim 1, wherein the oxide is silicon oxide and / or aluminum oxide.
A biodegradable laminated film having excellent gas barrier properties as described above.