JPH1059411A - Biodegradable container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the waterproofness of a container, and expand the application range to articles containing much moisture by a method wherein on the main surface of a molded body comprising 4 starch, a thin film layer comprising mainly silicon dioxide, is formed. SOLUTION: On the main surface of a molded body which forms a container comprising starch, i.e., on the surface which comes into contact with a content housed in the container, a thin film layer comprising mainly silicon dioxide is formed. In this case, the purpose of this thin film layer is to prevent the container from melting due to a contact with the content containing, e.g. hot water and the thin film layer may be formed at least limited to the surface which comes into contact with the content, of may be formed on the whole surface in order to prevent the container from melting when the content runs over to the outside of the container or spills. Since the thin film layer comprising mainly silicon dioxide does not permeate moisture, the thin film layer has a function to prevent starch from directly coming into contact with moisture. Therefore, such a container can have waterproofness without spoiling the characteristics owned by the molded body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable container having a biodegradable function that is naturally decomposed even when discarded in soil as garbage, and more particularly to a container for mainly hot foods.

[0002]

2. Description of the Related Art Conventionally, a polymer material such as polyethylene is used for a container for packaging food. Containers made of such polymer materials are used as containers for various foods because they are impermeable to moisture and do not deteriorate themselves when they come into contact with food. The heat-resistant temperature of a container made of such a polymer material is usually about 130 to 180 ° C., and has a property that can withstand a container of hot water. Moreover, it is also possible to provide heat insulation by foaming.
In addition, containers made of polymer materials are light and hard to break, which is a feature not found in pottery. It is often used as a container for noodles such as beverage cups and ramen. Most of these are used as disposable containers. Also, containers of polymeric materials are often used during barbecues and meals at outdoor events, which are also mostly disposable.

[0003]

As described above, containers made of a polymer material are widely used, but when they are discarded, they remain semi-permanently and cause environmental destruction. Concerns are growing. In particular, containers made of polymer materials are often disposable, and the problem of garbage has become a very serious problem. Further, containers made of a polymer material are often used outdoors, and there is a high possibility that they will be randomly disposed of in a natural environment.

[0004] Therefore, if decomposability can be imparted to these containers, the problem of environmental destruction due to their disposal can be solved. As a degradable material, starch is well known. Starch is a natural material obtained from cereals such as potatoes. Containers formed from this are not only naturally decomposed and returned to nature by disposal in the soil, but also become compost and mulch. Therefore, it is a material that can be suitably used as a material for disposable containers that are frequently used outdoors.

[0005] However, containers made of starch have resistance to oils and fats, but have low water resistance, and have a water content, especially 50%.
It melts when it comes in contact with hot water of at least ° C. Therefore, foods to which containers made of starch can be applied are limited to oily foods such as potato fries and noodles such as curry rice, ramen and the like, and cannot be used as food containers which are warm and have high moisture content. In view of the above circumstances, it is an object of the present invention to improve the water resistance of a container made of starch and to extend the range of use of the container to those containing a large amount of moisture.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, formed a thin film layer mainly composed of silicon oxide on the main surface of a molded body composed of starch. As a result, the inventors have found that water resistance can be imparted without impairing the properties of the molded article, and have reached the present invention.

That is, the present invention provides (1) a biodegradable container in which a thin film layer mainly composed of silicon oxide is formed on a main surface of a molded body composed of starch, and (2) a thin film layer mainly composed of silicon oxide. Is a biodegradable container according to (1), wherein the container is formed by a reduced pressure plasma chemical vapor deposition method using an organic silicon gas and an oxygen gas.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. First, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a sectional view showing an example of the biodegradable container of the present invention. In the figure, 10 is a molded body made of starch, 20
Is a thin film layer mainly composed of silicon oxide.

In the present invention, a thin film layer mainly made of silicon oxide is formed on a main surface of a molded body on which a container made of starch is to be formed. Here, the "principal surface" means a surface where the container comes into contact with the contents accommodated in the container. For example, in the container in FIG. However, the thin film layer made of silicon oxide is formed in order to prevent dissolution caused by the container coming into contact with the content containing hot water, for example, so long as it is formed at least on the surface in contact with the content. Good. Of course, when the content overflows or spills out of the container, it comes into contact with the surface on which the thin film layer made of silicon oxide is not formed, and silicon oxide is applied to the entire surface of the container in order to prevent the container from being dissolved therefrom. May be formed.

In the present invention, a molded article made of starch is used as a base of a container. Starch is obtained from cereals such as potatoes and wheat, but is most preferably used because potatoes are the most abundantly harvested. Starch is made of amylose having a small number of branches and amylopectin having a large number of branches. It is preferable to use so-called amylose starch having an increased amylose content. By increasing the amylose content, strength is improved and a tough substrate is obtained.

In the present invention, in order to process the starch into a molded article in the form of a container, water and a softener are added to the raw starch, and the starch is melted and extruded. The molded body of starch thus obtained has the necessary strength to be used as a container. Usually, this molded product is slightly milky and has an aesthetic appearance as a food container or tableware. Since this raw material is starch obtained from cereals, it is safe for living organisms so that the container itself can be eaten.

[0012] A molded article made of starch does not deteriorate at all when it comes in contact with fats and oils, but is dissolved when it comes into contact with water, especially warm water of 50 ° C or higher. Therefore, it can be used as a container for fat and oil foods such as potato fries, but is difficult to use as a container for curry rice, ramen and the like.

Therefore, in the present invention, a thin film layer mainly made of silicon oxide is formed on the main surface of a molded body on which a container made of starch is to be formed. Since the thin film layer mainly made of silicon oxide does not transmit moisture, it has a function of preventing direct contact between starch and moisture. Therefore, it is required that the thin film layer mainly made of silicon oxide be formed so as not to generate pinholes and cracks. Such pinholes often occur due to dust or dust adhering to the surface of the film molded body when forming the thin film layer. Therefore, it is preferable to wash the surface of the film molded body with air or the like before forming the thin film layer.
In addition, the film may be washed with an appropriate washing liquid as long as it does not cause deformation or deterioration of the film.

On the other hand, cracks in the thin film layer often occur due to shrinkage of the film formed by heat. Although a method for forming the thin film layer will be described later, it is usually preferable to use a method in which the temperature does not easily rise during the time of forming the thin film layer.

In the present invention, the thin film layer mainly composed of silicon oxide is transparent, has a high moisture barrier property, and
Since it also has high heat resistance, it is suitable as a layer for preventing the molded body made of starch in the present invention from coming into contact with moisture. In addition, since silicon oxide is a material that is largely contained in soil, even if it is discarded in soil as it is, there is no adverse effect on the environment. Furthermore, since the container according to the present invention basically uses starch having biodegradability as a molded body, when it is discarded in soil or seawater, there is of course no adverse effect on the environment, Since it is naturally decomposed into substances that are harmless to the human body, it is also useful for solving waste disposal problems.

As the method for forming the thin film layer in the present invention, a conventionally known method such as a physical vapor deposition method, a wet method, and a chemical vapor deposition method can be adopted. Specific examples of the physical vapor deposition method include a resistance heating vapor deposition method, an electron beam vapor deposition method, an ion plating method, and a sputtering method. In the resistance heating evaporation method and the electron beam evaporation method, silicon oxide is evaporated by a resistance heating method and an electron beam heating method, respectively, and is deposited on a film formed body arranged opposite to each other.
Further, a reactive evaporation method in which silicon is heated and evaporated in an oxidizing gas atmosphere, and an ion plating method in which silicon is evaporated in an oxidizing gas plasma can be used. On the other hand, in the sputtering method, a high-frequency sputtering method using silicon oxide as a target and using an inert gas such as argon or neon as a sputtering gas can be used. Alternatively, a direct current sputtering method using silicon as a target and a gas obtained by mixing an inert gas and an oxidizing gas as a sputtering gas,
Alternatively, a high frequency sputtering method can also be used.
Either method can provide a silicon oxide thin film layer having gas blocking performance. The physical vapor deposition method is an effective means when the object to be molded is flat. There is a problem that formation is difficult. In the present invention, when the molded body is concave, there is a concern that a thin film may not be sufficiently formed on the side surface.

The wet method includes, for example, a sol-gel method. In the wet method, a method in which a solution in which polysilazane is melted is applied and heated in the air or in a steam atmosphere to form silicon oxide is also used. The polysilazane _{here, (SiN a H b) n} (a = 1~3, b = 0
Perhydropolysilazane having the structure of 1),
Only hydrogen is bonded to (-Si-N-) of the main chain as a side chain. Since the polysilazane can be dissolved in a solvent such as benzene, toluene, xylene, ether, THF, methylene chloride, or carbon tetrachloride in an amount of 20% by weight or more, the polysilazane is dissolved in these solvents, and then applied to a film molded product. By performing the heat treatment, silicon oxide can be obtained. Generally, to obtain inorganic silicon oxide, 45
Although heat treatment at 0 ° C. or higher is required, use of a catalyst of an amine or a transition metal at a low temperature, for example, at 80 ° C.
Inorganic silicon oxide is obtained by a heat treatment at ~ 150 ° C. The heat treatment time at this time is generally about 1 to 3 hours. The polysilazane used for coating has a molecular weight of 60.
Those having 0 to 900 are preferably used. The wet method is also a simple method when the molded body is flat, but it is difficult to uniformly apply the coating liquid when the molded body has a curved surface. In particular, it is necessary to take measures to prevent the liquid applied to the side from dripping down.

The chemical vapor deposition method is a method in which an organic silicon compound is used as a raw material, and is decomposed by applying energy to the organic silicon compound to precipitate silicon oxide, which is an inorganic substance. There are heat, light, high-frequency plasma, and the like as a method of inputting energy, and may be appropriately selected. In the chemical vapor deposition method, since the vapor of an organic silicon compound is used as a raw material, silicon oxide is formed irrespective of the unevenness of the surface of the molded body. Is formed. Further, even when the surface smoothness is not so high, the surface covering property is high, and it can be most preferably used as a method for forming a silicon oxide film for the purpose of completely blocking moisture. Above all, the low pressure plasma chemical vapor deposition method can be more preferably used because silicon oxide having excellent moisture barrier properties can be formed without damaging the formed body.

When silicon oxide is formed by a low pressure plasma chemical vapor deposition method, it is preferably formed using at least an organic silicon compound and oxygen gas. Specific examples of the organic silicon compound used include acetoxytrimethylsilane, allyloxytrimethylsilane, allyltrimethylsilane, bistrimethylsilyl adipate, butoxytrimethylsilane, butyltrimethoxysilane, cyclohexyloxytrimethylsilane, decamethylcyclopentasiloxane, and decamethylcyclopentasiloxane. Methyltetrasiloxane, diacetoxydimethylsilane, diacetoxymethylvinylsilane, diethoxydimethylsilane, diethoxydiphenylsilane, diethoxy-3-glycidoxypropylmethylsilane, diethoxymethyloctadecylsilane, diethoxymethylsilane, diethoxymethylphenyl Silane, diethoxymethylvinylsilane, dimethoxydimethylsilane, dimethoxydiphenylsilane, dimethoxymethylsilane Nirushiran, dimethylethoxy phenylsilane, dimethyl ethoxy silane, dimethyl isopentyloxy vinyl silane, 1,3-dimethyl -1,1,3,3
-Tetraphenyldisiloxane, diphenylethoxymethylsilane, diphenylsilanediol, 1,3-divinyl-1,1,3,3-tetramethyldisilane,
-(3,4-epoxycyclophenylethyl) trimethoxysilane, ethoxydimethylvinylsilane, ethoxytrimethylsilane, ethyltriacetoxysilane, ethyltriethoxysilane, ethyltrimethoxysilane, ethyltrimethylsilane, 3-glycidoxypropyltrimethoxy Silane, 1,1,1,3,5,5,5-heptamethyltrisiloxane, hexamethylcyclotrisiloxane, hexamethyldisiloxane, hexyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-methacryloxypropyl Trimethoxysilane,
Methoxytrimethylsilane,

Methyltriacetoxysilane, methyltriethoxysilane, methyltrimethoxysilane, methylisopropenoxysilane, methylpropoxysilane, octadecyltriethoxyethoxysilane, octamethylcyclotetrasiloxane, 1,1,1,3,5, 7,7,
7-octamethyltetrasiloxane, octamethyltrisiloxane, octyltriethoxysilane, 1,3
5,7,9-pentamethylcyclopentasiloxane, pentamethyldisiloxane, 1,1,3,5,5-pentaphenyl-1,3,5-trimethyltrisiloxane, phenyltriethoxysilane, phenyltrimethoxysilane, Phenyltrimethylsilane, propoxytrimethylsilane, propyltriethoxysilane, tetraacetoxysilane, tetrabutoxysilane, tetrateethoxysilane, tetraisopropoxysilane, tetramethoxysilane, 1,3,5,7-tetramethoxycyclotetrasiloxane, 1,1,3,3-tetramethyldiloxane,
Tetramethylsilane, 1,3,3,5-tetramethyl-1,1,5,5-tetraphenyltrisiloxane, 1,
3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, tetrapropoxysilane, triacetoxyvinylsilane, triethoxyvinylsilane, triethylsilane, trihexylsilane, trimethoxysilane, trimethoxyvinylsilane, Trimethylsilanol, 1,3,5-trimethyl-1,3,5-
Trivinylcyclotrisiloxane, trimethylvinylsilane, triphenylsilanol, tris (2-methoxyethoxy) vinylsilane, and the like can be used, but are not limited thereto, and aminosilane,
Silazane is also used.

In order to introduce the above organic compounds into the reaction vessel, a rare gas such as helium or argon can be used as a carrier gas. Alternatively, the organic silicon compound may be heated to increase the vapor pressure, and the organic silicon gas may be directly introduced. Instead of oxygen gas, a gas having an oxidizing effect, for example, ozone, water vapor, laughing gas, or the like may be used. The ratio of the flow rate of the introduced organic silicon gas to the flow rate of the oxygen gas depends on the type of the organic silicon compound, but is preferably in the range of the flow rate ratio of oxygen gas / organic silicon gas = 0.2 to 1.2.
When a rare gas such as helium is used as the carrier gas, the range of the flow rate of the organic gas and the flow rate of the oxygen gas in helium is preferably in the range of 0.2 to 1.2. If the oxygen flow rate is too low, the light transmittance and gas barrier properties of the resulting film decrease, and if the oxygen flow rate is too high, the adhesion and gas barrier properties of the film decrease. In addition, the pressure during the reaction may be within a range in which plasma discharge occurs, and is preferably 0.05 to 2.5 Torr, and more preferably 0. 1 to 1.5 Torr. If the pressure is too low, it becomes difficult to maintain the plasma discharge, and if the pressure is too high, the adhesion of the film tends to decrease. However, when using electron cyclotron resonance discharge, helicon wave discharge, or magnetron discharge that can be discharged at a lower pressure, the pressure range is not limited to the above range. For the measurement and control of the flow rate, a mass flow controller, a float type flow meter, a bubble meter and the like can be used. For measuring the pressure, a Pirani vacuum gauge, a diaphragm vacuum gauge, a spinning rotor vacuum gauge, a heat conduction vacuum gauge, an ionization vacuum gauge, or the like can be used, but a diaphragm vacuum gauge is preferably used.

The thickness of the silicon oxide layer formed as described above is not particularly limited, but it is within a range that does not impair the transparency, maintains the gas barrier property, and adheres to the polymer substrate. Any thickness can be used as long as it can secure Specifically, the thickness is preferably 20 nm to 500 nm, more preferably 20 nm to 500 nm.
-100 nm is more preferable. If the thickness of the silicon oxide layer is too small, it is desirable to form a uniform and continuous film. Conversely, if the thickness is too large, the adhesion to the film formed body is reduced, or the silicon oxide layer is easily broken. To measure the film thickness, there are a stylus roughness meter, a repetitive reflection interferometer, a microbalance, a crystal oscillator method, and the like. It is suitable for obtaining a desired film thickness while monitoring with. In addition, the conditions for the film formation are determined in advance, and the film is formed on the test base material.
After examining the relationship between the film formation time and the film thickness, a method of controlling the film thickness by the film formation time can also be adopted.

The silicon oxide may contain trace amounts of iron, nickel, chromium, titanium, magnesium, aluminum, indium, zinc, tin, antimony, tungsten, molybdenum, copper and the like. For the purpose of improving the flexibility of the film, carbon or fluorine may be appropriately contained.

The composition of silicon oxide in the present invention is not particularly limited as long as gas barrier performance is obtained and transparency is maintained. Although silicon oxide can be generally described as SiOx, the range of x is usually about 1.0 to 2.5.

The composition of the thin film layer made of silicon oxide can be analyzed using X-ray photoelectron spectroscopy, X-ray microanalysis, Auger electron spectroscopy, Rutherford backscattering, or the like. For example, when the Rutherford backscattering method is used, a sample film is placed in a vacuum vessel, and α-particles accelerated to 1 to 4 MeV are irradiated from the surface of the sample to analyze the energy of ions backscattered. This makes it possible to investigate the composition of the film in the depth direction and the uniformity of the composition. Gold or the like may be appropriately deposited on the surface to prevent charging of the surface layer. In the case of performing an analysis by Auger electron spectroscopy, a specimen is placed in an ultra-high vacuum vessel, and the surface of the specimen is irradiated with an electron beam accelerated to 1 to 10 keV. The composition can be examined by detecting In this case, since the electrical resistance of the specimen may be high, the current of the primary electron beam is suppressed to 10 pA or less so that the influence of charging is not exerted.
It is preferred to be less than keV. X instead of electron beam
Photoelectron spectroscopy using lines is advantageous in that it is less affected by charging than Auger electron spectroscopy.

When a thin layer of silicon oxide is formed on the main surface of a molded body made of starch, corona discharge treatment, plasma treatment, glow discharge treatment,
A reverse sputtering treatment, a surface roughening treatment, a chemical treatment or the like can be performed, or a known undercoat can be applied.

[0027]

The present invention will be described below with reference to examples. [Example] Water was added to amylose starch, which was formed into a dish shape by a melt extrusion method, dried and evaporated to obtain a molded product made of starch in a starch-like shape. On the inner surface of the container, 40
Tetramethyldisiloxane (hereinafter referred to as TMD)
SO) (abbreviated as SO) at a flow rate of oxygen / TMDSO = 0.5 into the vacuum vessel, and while maintaining a degree of vacuum of 0.1 Torr, a high frequency of 13.56 MHz was introduced into the parallel plate electrode to generate plasma. Discharge was performed, and a 100-nm-thick silicon oxide layer was formed by a reduced-pressure plasma-enhanced chemical vapor deposition method, whereby a container was manufactured.

[Comparative Example] A molded body made of starch was obtained in the same manner as in the example, but a silicon oxide layer was not formed and used as it was as a container. Warm water at 90 ° C. was poured into the containers obtained in the examples and the comparative examples, which were left in a room as it was, and the presence or absence of deterioration was visually checked. [Table 1] summarizes the results.

[0029]

[Table 1]

As shown in Table 1, the product of the present invention did not undergo any alteration, such as melting, while the conventional product melted when warm water was added. From this result, it can be seen that the container of the present invention can be suitably used even if the content temperature is hot water, for example, curry rice or ramen. Since starch used as a raw material of the container has biodegradability, it is naturally decomposed even when it is disposed of in soil or seawater.

[0031]

According to the present invention, it is possible to provide a container which is naturally decomposed even when discarded in soil or seawater and does not remain as garbage, and which is additionally provided with warm water resistance. If this is used as a container for disposable foods that are currently consumed in large quantities, such as curry dishes and bowls of noodles, it will not become garbage even if discarded, so that environmental destruction can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a biodegradable raw container of the present invention.

[Explanation of symbols]

 Reference Signs List 10 starch molded body 20 silicon oxide layer

Claims (2)

[Claims] 1. A biodegradable container formed by forming a thin film layer mainly composed of silicon oxide on a main surface of a molded body composed of starch. 2. The biodegradable container according to claim 1, wherein the thin film layer mainly made of silicon oxide is formed by a low pressure plasma chemical vapor deposition method using an organic silicon gas and an oxygen gas.