JPH04299131A - Vessel for food - Google Patents

Abstract

PURPOSE:To enable natural decomposition of vessels scattered about on the ground, by a method wherein the vessels holding food which are molded by an injection molding or thermoforming method are formed of a single layer or laminated body of a decomposable material decomposed by light or microbes. CONSTITUTION:In a cuppy or traylike vessel 1 for food which is formed by an injection molding method or a thermoforming method, a single layer or a laminated layer of a decomposable material is used as its material. In case of a form of the single, layer, the decomposable material is regarded as a polyolefin resin such as decomposable polyethylene resin and decomposable polypropylene or polyvinyl alcohol or decomposable polyester. In case of the laminated body, for example, an inner layer 21 is regarded as decomposable polyolefin resin and an outer layer 25 is regarded as the polyvinyl alcohol or the decomposable polyester.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to containers for storing food;
In particular, the present invention relates to a food container formed by injection molding or thermoforming and made of a degradable material.

0002

[Prior Art] In recent years, plastic containers have been replaced by glass bottles,
Compared to cans, it is lighter, more durable, easier to transport and store, and is cheaper, so its demand is increasing. Among such plastic containers, there are containers that are intended to contain only food and are formed by injection molding or thermoforming. Such containers are frequently used in people's daily lives, and the demand for them is increasing year by year.

[0003] By the way, in order to dispose of plastic containers after use, including containers formed by injection molding or thermoforming, conventional methods have had to rely on incineration or landfilling, making it difficult to dispose of plastic waste. , is currently attracting attention as a major social problem. That is, incineration processing requires a high-temperature resistant furnace that can withstand a large amount of combustion energy of packaging material waste, resulting in high processing costs. In addition, in landfill processing, plastic packaging materials do not decompose and remain underground, so there is a problem that the ground at the landfill site is unstable. Furthermore, since the packaging materials scattered on the ground are not degradable, they remain as garbage semi-permanently, which poses a problem of damaging the environment.

[0004] In order to solve these problems, proposals have been made to use so-called degradable plastic materials.

[0005]

[Problems to be Solved by the Invention] However, in the conventional proposals, the container is made by injection molding or thermoforming, and is degradable. No food containers were present. In view of the above-mentioned circumstances, the present invention has been devised, and its purpose is to provide a food container formed by injection molding or thermoforming and having degradability.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a container for storing food formed by an injection molding method or a thermoforming method, the container comprising a single layer of a degradable material. Or, it was configured to be formed from a laminate.

[0007]

[Operation] Since the food container of the present invention is made of degradable material,
It decomposes naturally even after normal storage.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 3. The food container of the present invention is a container for storing food, and is particularly intended for containers formed by injection molding or thermoforming. Injection molding containers are made by feeding granular thermoplastic resin into one end of a heating cylinder, compressing it into the cylinder by advancing a plunger, heating it to make it fluid, and injecting it into a cold mold through a nozzle.
This method involves cooling, solidifying, and molding.

[0009] The thermoforming method is a method of heating and softening a thermoplastic plastic sheet and forming it into the shape of a mold using vacuum or compressed air. The food container formed in this way is
There are cup-shaped containers, tray-shaped containers, etc., and FIG. 1 shows a cup-shaped food container 1. Such a container 1
has a container-shaped storage section E for storing food, and the container itself is formed from a single layer or a laminate of degradable materials.

In the case of a single layer, the degradable material is made of a degradable plastic, particularly a degradable polyolefin resin such as a degradable polyethylene resin or a degradable polypropylene resin, polyvinyl alcohol, or a degradable polyester. Degradable polyolefin resin is a resin that is mainly composed of polyethylene or polypropylene and can be decomposed by light or microorganisms.

Among the degradable polyolefin resins, photodegradable ones include copolymers of ethylene and carbon monoxide. This ethylene/carbon monoxide copolymer is said to be decomposed by light cleavage between the second and third carbons to which the carbonyl group is bonded. The decomposition rate can be controlled by the carbon monoxide content in the copolymer. Usually, the density of the ethylene/carbon monoxide copolymer is about 0.89 to 0.95 g/cm@3, and the carbon monoxide content is about 0.1 to 10 mol%.

[0012] The above-mentioned ethylene/carbon monoxide copolymer can be prepared by, for example, mixing ethylene and carbon monoxide at a temperature of 230°C.
It can be produced by allowing them to coexist under conditions of a pressure of about 2000 atmospheres. In addition, polyethylene (density 0.870~
0.950g/cm3, melting index (MFI) 0.4~
40), polypropylene (density 0.88-0.91g/
cm3, melting index (MFI) 0.2 to 60) and an organic acid metal salt can also be used. Examples of metal compounds include iron stearate, cerium stearate, cobalt stearate, etc., and metal oxides such as iron oxide, complexes with acetylacetone, dibutyl dithiocarbamate, etc., and the mixing amount of these metal compounds is 1 ~5
000 ppm is preferable.

[0013] A copolymer with vinyl ketone may also be added. Furthermore, among the degradable polyolefin resins, examples of those degradable by microorganisms include mixtures of polyethylene and polypropylene with polycaprolactone, starch, and polyester polymerized by microorganisms. Polyethylene used for biodegradable polyolefin resin has a density of 0.870 to 0.950 g/cm
3. Ethylene homopolymer with a melting index (MFI) of 0.4 to 40, or propylene, hexene, octene,
Random or block copolymers with other olefins such as 4-methylpentene-1, as well as ethylenic copolymers such as vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, maleic anhydride, etc. Examples include copolymers with monomers having unsaturated groups. Density 0.88-0.9 for polypropylene
Examples include copolymers of propylene and monomers having ethylenically unsaturated groups such as ethylene, butene-1, maleic anhydride, etc., with a melting index (MFI) of 1 g/cm3 and a melting index (MFI) of 0.2 to 60.

[0014] Polycaprolactone used in the biodegradable polyethylene resin is obtained by ring-opening polymerization of ε-caprolactone, and its weight average molecular weight (Mw) is usually about 40,000 to 100,000. Also,
Starch is a polymer of D-glucose and is industrially produced from the stems and roots of potatoes, sweet potatoes, corn, wheat, etc., and its weight average molecular weight (M
w) varies greatly, from tens of thousands to tens of millions, depending on the raw materials and manufacturing method. The average particle size of such starch is preferably 10 μm or less.

The polyester polymerized by microorganisms used in the biodegradable polyethylene resin includes a random copolymer polyester of 3-hydroxybutyrate and 3-hydroxyvalerate (for example, a polyester produced by I.C.I., UK). (obtained by supplying propionic acid to hydrogen bacteria) and 3-hydroxybutyrate-based polyesters obtained by supplying valeric acid to hydrogen bacteria.

The amount of polycaprolactone, starch, and polyester polymerized by microorganisms in the above-mentioned biodegradable polyethylene resin is 5 to 80% by weight, with the total of the polyolefin and each of the above mixed components being 100% by weight. is preferred. If the mixing amount of each of the above components is less than 5% by weight, the microbial degradability will be insufficient, and if it exceeds 80% by weight, the strength will be weakened.

[0017] Note that two or more of each component of polycaprolactone, starch, and polyester polymerized by microorganisms may be used, but in that case, the total mixing amount is 5 to 5.
The content may be within the range of 80% by weight. Furthermore, by using the photodegradable polyolefin resin described above as a raw material for the microbially degradable polyolefin resin, it is possible to obtain a degradable polyethylene resin that is both photodegradable and microbially degradable.

As the degradable polyester, the aforementioned polycaprolactone or polyester polymerized by microorganisms can be used alone. Moreover, as polyvinyl alcohol, one having a degree of saponification of 99% or more is usually used. These may also contain the above-mentioned inorganic substances. In addition, some of these degradable polyethylene resins contain calcium carbonate, magnesium carbonate,
Metal salts such as calcium sulfate, calcium sulfite, barium sulfate, magnesium sulfate, silicic acid or kaolin,
It may contain inorganic fillers such as silicates such as talc, metal oxides such as titanium oxide and zinc oxide, and aluminum compounds such as aluminum hydroxide and alumina. Furthermore, various additives such as antioxidants, decomposition promoters, stabilizers, antistatic agents, and surfactants may be included.

Various embodiments of cross-sections in the case of laminates are shown in FIG. 2 or 3. Both are made of degradable materials. FIG. 2 shows a partial cross-sectional view of one embodiment of the laminate. As shown in FIG.
It has a laminated structure of layers, for example, the inner layer 21 is formed of the above-mentioned degradable polyolefin resin, and the outer layer 25 is formed of polyvinyl alcohol or degradable polyester. These two
Another resin having good heat-fusibility may be interposed between the layers as an adhesive layer. The thickness of the inner layer 21 is usually 10 to 200 mm.
It is about 0 μm. Further, the thickness of the outer layer 25 is usually 1
It is about 0 to 2000 μm.

FIG. 3 shows a partial sectional view of another embodiment of the laminate. As shown in FIG. 3, the container 1 has a three-layer laminated structure, with an inner layer 21 and an outer layer 35 sandwiching an intermediate layer 30 therebetween. In this case, the inner layer 21 and the outer layer 35 are each formed from the above degradable polyolefin resin, and the intermediate layer 30 is formed from polyvinyl alcohol or degradable polyester. Another resin having good heat-fusibility may be interposed between these layers as an adhesive layer. The thickness of the inner layer 21 and the outer layer 35 is usually about 10 to 2000 μm. Further, the thickness of the intermediate layer 30 is usually about 10 to 2000 μm.

[0021] In addition, various laminates can be formed by appropriately combining the various degradable plastics mentioned above.

[0022]

[Effects of the Invention] Since the container of the present invention is made of a degradable material, it has the effect of being degradable.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a container of the invention.

FIG. 2 is a partial cross-sectional view showing the layer structure of the container of the present invention.

FIG. 3 is a partial cross-sectional view showing another layer structure of the container of the present invention.

[Explanation of symbols]

1 Container

Claims (1)

[Claims] 1. A container for storing food formed by injection molding or thermoforming, characterized in that the container is formed from a single layer or a laminate of degradable materials. .