Packaging materials

Abstract

To provide a packaging material or a container in which decomposition of a biodegradable resin constituting the packaging material or container is started by a decomposition promoting substance contained in the biodegradable resin receives a physical stimulation and acts on the biodegradable resin when the packaging material or container is opened.SOLUTION: A packaging material or container comprises a biodegradable resin and microcapsules containing a decomposition-promoting substance for the biodegradable resin, wherein the microcapsules each comprise an outer shell comprising a photo-degradable resin composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a packaging material or container using a biodegradable resin containing microcapsules encapsulating microorganisms or enzymes capable of decomposing the biodegradable resin.

Background Art

[0002] Plastic products widely used throughout the industry are not easily decomposed in the natural environment and remain in the soil and ocean for a long time. Therefore, in order to reduce the burden on the natural environment, various biodegradable plastics that can be decomposed by microorganisms are used. Products using biodegradable plastics are gradually increasing. However, there are few examples of treatment methods that utilize the decomposition conditions of individual biodegradable plastics at the time of disposal (for example, in the case of biodegradable plastics using polylactic acid, they are put into compost for biodegradation). Therefore, biodegradable plastics are generally incinerated in the same way as general synthetic resins. Thus, if the material flow remains the same as before, it is difficult to say that biodegradability itself contributes to environmental consideration for products. In addition, durable goods made of biodegradable plastics are recovered through the recycling route, but non-durable goods such as packaging materials, protective materials, and packaging films are discarded as general waste after their function is completed. In order for biodegradable plastics to be decomposed into water and carbon dioxide, the presence of microorganisms that secrete enzymes capable of decomposing the biodegradable plastics is essential, and it takes a long time to completely decompose after being buried in the soil. Therefore, when buried as general waste, they remain in the soil in their original form for a long time until they are decomposed, which becomes a factor of environmental burden. Therefore, in order to quickly decompose the biodegradable resin after disposal, a technology is known in which microcapsules encapsulating microorganisms or enzymes capable of decomposing the biodegradable resin are contained in the biodegradable resin (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] However, the biodegradable resin described in Patent Document 1 begins to decompose only after it has been discarded and the resin itself has been crushed. Therefore, if the resin is not properly crushed during collection or landfill, it will be difficult for the decomposition of the resin to begin, and it will take a long time to decompose. Taking the packaging material for electronic devices as an example, it is desirable that the packaging material (biodegradable resin) decomposes quickly after the product has been removed, while protecting the product from the external environment until just before use.

[0005] The present invention aims to provide packaging materials or containers in which, upon opening the packaging material or container, a decomposition-promoting substance contained in the biodegradable resin constituting the packaging material or container is physically stimulated and acts upon the biodegradable resin, thereby initiating the decomposition of the biodegradable resin. [Means for solving the problem]

[0006] The inventors, after various studies to solve the above problems, encapsulated microorganisms or enzymes, which act as degradation-promoting substances that accelerate the degradation of biodegradable resins, in microcapsules equipped with a photodegradable outer shell that can be degraded by light irradiation. They then found that the above problems could be solved by producing packaging materials or containers using a biodegradable resin composition containing these microcapsules and biodegradable resin, and thus completed the present invention.

[0007] One aspect of the present invention is a packaging material or container containing a biodegradable resin and microcapsules containing a substance that promotes the degradation of the biodegradable resin, wherein the microcapsules have an outer shell containing a photodegradable resin composition. [Effects of the Invention]

[0008] According to the present invention, when the packaging material or container is opened, a decomposition-promoting substance contained in the biodegradable resin constituting the packaging material or container is physically stimulated and acts on the biodegradable resin, thereby enabling the decomposition of the biodegradable resin to begin. [Brief explanation of the drawing]

[0009] [Figure 1] These are a plan view and a side view of a gusseted bag with a gusset according to one aspect of the present invention. [Figure 2] This is a schematic plan view of a gusseted bag with a gusset according to one aspect of the present invention. [Figure 3] Figure 2 is a schematic cross-sectional view of section AA of the gusseted bag with a gusset. [Figure 4] This is a schematic diagram of a gusseted bag with a gusset according to one aspect of the present invention. [Modes for carrying out the invention]

[0010] The packaging material or container according to the present invention contains a biodegradable resin and microcapsules containing a substance that promotes the degradation of the biodegradable resin. Specifically, the packaging material or container according to the present invention is composed of a biodegradable resin composition comprising a biodegradable resin and microcapsules containing a substance that promotes the degradation of the biodegradable resin. The microcapsules are characterized by having an outer shell containing a photodegradable resin composition. Embodiments of the present invention will be described in detail below.

[0011] [Biodegradable resin] The biodegradable resin (biodegradable plastic) is not particularly limited and includes common biodegradable resins such as PLA (polylactic acid), PHA (polyhydroxyalkanoic acid), PHB (poly(3-hydroxybutyrate)), PBS (polybutylene succinate), PPL (poly(β-propiolactone)), PCL (poly(ε-caprolactone)), and PEA (polyethylene adipate). From these, a resin suitable for the properties required for packaging or containers can be used individually or in polymer blends or graft polymerization of two or more types. Furthermore, the above biodegradable resin may be chemically modified with other biodegradable synthetic polymers before use.

[0012] [Microcapsules] A microcapsule consists of an internal substance called a "core substance" and a capsule called an "outer shell" that encloses the core substance. In the microcapsule according to the present invention, the core substance is a decomposition-promoting substance that accelerates the decomposition of biodegradable resin, and the outer shell contains a photodegradable resin composition. In the present invention, the size of the microcapsule can be 1 to 50 μm.

[0013] (decomposition accelerating substance) As decomposition-promoting substances to accelerate the decomposition of biodegradable resins, microorganisms capable of decomposing each biodegradable resin, enzymes secreted by such microorganisms, or equivalent chemical substances are used. For example, for PBS and PLA, actinomycetes of the genus Amycolatopsis are known; for PPL, PHB depolymerase and lipase; for PEA and PCL, strains of the genus Penicillium; and for PHB (poly(3-hydroxybutyrate), strains of the genera Bacillus, Pseudomonas, and Streptomyces are known.

[0014] In addition to the microorganisms or enzymes mentioned above, the decomposition rate can be further increased by using an oxidative accelerator that reduces the molecular weight of the biodegradable resin as a decomposition accelerator. Examples of oxidative accelerators include known metal oxides and oxidizing substances. The microorganisms or enzymes and the oxidative accelerator may be encapsulated in different microcapsules. Alternatively, the microcapsules may have a multilayer structure, with the oxidative accelerator placed in the outer layer and the microorganisms or enzymes that decompose the biodegradable resin placed in the inner layer.

[0015] From the viewpoint of resin molding and material mechanics properties, the amount of decomposition-accelerating substance added is preferably 1 to 20% by mass relative to the total amount of biodegradable resin. If the amount of decomposition-accelerating substance added is within the above range, there is no risk of affecting strength properties, environmental resistance, and logistical and storage properties. Microcapsules are added to the biodegradable resin so that the amount of decomposition-accelerating substance added to the biodegradable resin is within the above range.

[0016] (Photodegradable resin composition) The outer shell of the microcapsule according to the present invention contains a resin composition that is photodegradable (photodegradable). In other words, the microcapsule according to the present invention is a microcapsule that is photodegradable. The energy of sunlight is less than the CC bond energy, which is the main chain bond of polymer chains. Therefore, photodegradation of plastics occurs by generating radicals in the polymer chains photochemically, which then promotes oxidation reactions. Specifically, by irradiating the photosensitizer with light in a wavelength range sensitive to the photosensitizer, the photosensitizer is excited into an excited triplet state, which then extracts hydrogen atoms from the polymer (oxidation). Alternatively, energy is transferred from the photosensitizer to oxygen molecules, generating singlet oxygen, which then reacts with the polymer to proceed.

[0017] As a general photodecomposition reaction, the Norrish reaction, which is a photodecomposition reaction of carbonyl compounds (ketones, aldehydes), is known. In the Norrish type I reaction (Type I), the carbonyl compound is excited by light irradiation, and the bond at the α-position of the carbonyl group is cleaved to generate two radicals via a radical pair, and the reaction proceeds via a radical mechanism (the following formula (1)). On the other hand, in the Norrish type II reaction (Type II), the hydrogen atom bonded to the γ-carbon is abstracted by the excited carbonyl oxygen to give a biradical. The generated biradical cleaves the carbon-carbon bond between the α-position and the β-position and decomposes into a ketone and an olefin (the following formula (2)), or recombines intramolecularly to form a cyclobutanol derivative. In the case of a polymer having no carbonyl group in the molecule, photodecomposition is also carried out by introducing a carbonyl group via oxidation.

[0018]

Chemical formula

[0019] The resin composition having photodegradability preferably contains a resin having one or more photoexcitable structures selected from unsaturated bonds such as a carbonyl group or a carbon-carbon double bond. Examples of such resins include polymers or copolymers containing, as monomers, ethylenically unsaturated carboxylic acids such as (meth)acrylic acid and (meth)acrylic acid esters, and esters thereof. In the present invention, “(meth)acrylic acid” means acrylic acid or methacrylic acid, and “(meth)acrylic acid ester” means acrylic acid ester or methacrylic acid ester. A resin composition having photo-disintegrating properties can be obtained by mixing a resin such as an acrylic polymer or polyvinyl alcohol, which is usually used to form the outer shell of a capsule, with a photo-decomposing agent having an absorption wavelength in the ultraviolet to visible light range. Examples of photo-decomposing agents include photosensitizers that cause a hydrogen abstraction reaction from the polymer by photoexcitation, such as aromatic ketones like benzophenone and quinones like anthraquinone; dithiocarbamate salts such as iron dithiocarbamate and copper dithiocarbamate that are easily decomposed by light; and compounds having unsaturated bonds such as carbon-carbon double bonds and carbon-carbon triple bonds that generate aromatic ketones upon light irradiation, such as aromatic dienes and aromatic trienes. Among these, it is preferable to use a photosensitizer as the photo-decomposing agent.

[0020] In addition, a resin composition having photo-disintegrating properties can be obtained by introducing photo-disintegrating functional groups such as azo groups, carbonyl groups, and ether groups into the resin usually used to form the outer shell of the capsule. Alternatively, a polymer alloy having such functional groups may be used to form the outer shell of the capsule. For example, a resin composition having photo-disintegrating properties can be formed by adding an azobenzene compound to an acrylic polymer and using a polymer containing a photo-disintegrating functional group in its structure as a single polymer or a copolymer. Or, when using a resin itself having photo-disintegrating properties and having one or more photo-excitable structures selected from unsaturated bonds such as a carbonyl group or a carbon-carbon double bond, it may be used as a resin composition having photo-disintegrating properties composed of the resin having photo-disintegrating properties. Further, in order to increase the sensitivity, a photosensitizer having sensitivity in the ultraviolet to near-infrared range may be added to the resin having photo-disintegrating properties.

[0021] Note that the presence of oxygen is required for the decomposition of the resin constituting the outer shell of the microcapsule by light. Therefore, when putting the product into the prepared packaging material or container for use, it is preferable to remove oxygen by making the inside of the packaging material or container a nitrogen atmosphere or degassing it.

[0022] In the packaging or container according to the present invention, while the product is sealed inside the packaging or container, the interior is shielded from light, so the degradation-promoting substance contained in the microcapsules does not act. Then, when the packaging or container is opened, light enters the interior, and the degradation of the biodegradable resin is rapidly initiated. Specifically, when removing the product from the packaging or container according to the present invention, when the packaging or container is opened, natural light enters the surface where the torn portion was opened and the inside of the packaging or container (the side in contact with the product, hereinafter also referred to as the "product side") is exposed. Then, the light that enters the outer shell of the microcapsules placed in the biodegradable resin decomposes the photodegradable resin composition contained in the outer shell, and the degradation-promoting substance inside the microcapsule is slowly released through the gap created in the outer shell, initiating the degradation of the biodegradable resin.

[0023] The packaging material or container according to the present invention can be manufactured, for example, as follows: First, a photodegradable agent is added to the resin constituting the outer shell of a microcapsule to prepare a photodegradable resin composition. Next, microcapsules containing a decomposition-promoting substance are prepared using the resin composition by a known method. Subsequently, the obtained microcapsules are added to a biodegradable resin to obtain a biodegradable resin composition. A film is processed using the biodegradable resin composition, and the resulting film is made into a bag to obtain the packaging material or container according to the present invention. The shape and size of the packaging material or container may be appropriately selected according to the product to be used.

[0024] Microcapsules containing decomposition-promoting substances may be uniformly dispersed in a biodegradable resin, but it is preferable to create an uneven distribution of microcapsule concentration within the packaging or container. For example, a larger number of microcapsules may be placed on the inside (product side) of the packaging or container, so that the concentration of microcapsules on the inside of the packaging or container is higher than the concentration on the outside (surface side). Alternatively, a concentration distribution of microcapsules may be created within the plane of the inner surface of the packaging or container, or in the depth direction or plane from the outside (surface) of the packaging or container.

[0025] Furthermore, the following methods can be used to create a concentration bias of microcapsules within the packaging material or container, that is, to create areas with a high concentration of microcapsules. Specifically, this involves controlling the amount of microcapsules added to the biodegradable resin to create a concentration distribution. This can be done by a solution coating method or a spray coating method in which microcapsules are added afterwards. Additionally, methods for creating a concentration bias within the plane of the packaging material or container include coating or spraying microcapsules or a microcapsule-containing resin solution onto the area of ​​the biodegradable resin corresponding to the area where the microcapsules are encapsulated or the area with a high concentration of microcapsules.

[0026] The exposure environment to light at the opening point of the packaging or container when a user uses it varies. Furthermore, if the biodegradable resin has high transparency or low gas barrier properties against oxygen, it may be necessary to adjust the decomposition acceleration effect. One method for adjusting the decomposition acceleration effect of biodegradable resin within the product's warranty period is to adjust the amount of incident light by appropriately placing printed areas on the packaging or container that have a printed layer indicating the opening method, product name, logo, and precautions. For example, as shown in Figure 3, a printed layer 104 is provided as a surface layer on the outside (surface) of the packaging, and a microcapsule encapsulation area 105 is provided below this printed layer (closer to the product side). With this configuration, the amount of light incident on the microcapsules can be adjusted by attenuating or blocking light from the surface with the printed layer. In this case, more microcapsule encapsulation areas may be placed closer to the inside (product side) of the packaging. Here, the microcapsule encapsulation region means that microcapsules are encapsulated only in that region. However, a region with a higher concentration of microcapsules may be provided below the printed layer instead of the microcapsule encapsulation region. The microcapsule encapsulation region can be formed, for example, by applying or spraying microcapsules or a microcapsule-containing resin solution to a region corresponding to the microcapsule encapsulation region of a biodegradable resin.

[0027] The colorants used for the printing layer can be pigment-based or dye-based, as long as they are the same colorants commonly used for packaging or containers; the type is not particularly restricted. However, it is preferable to form the printing layer by printing with known biodegradable inks. The printing area is intended to provide a light-blocking effect by printing text such as logos and opening instructions, but the entire area may also be colored with a light-blocking colorant in addition to the text. When a printing layer is provided, it does not necessarily have to be on the outermost surface of the packaging or container; it is sufficient that the microcapsule encapsulation area (or the area with a high concentration of microcapsules) is located inside the packaging or container (on the product side) above the printing layer.

[0028] On the other hand, one method to accelerate the decomposition-promoting effect is to provide an easily openable section with an easily openable structure on the packaging material or container. By providing an easily openable section, the inner surface (product side) of the packaging material or container is more easily exposed to light when opened. Furthermore, by providing a region with a high concentration of microcapsules around the easily openable section, light is reliably irradiated onto the microcapsules when opened, further promoting the decomposition of the biodegradable resin by the disintegration of the microcapsules and the release of decomposition-promoting substances. Specifically, as shown in Figure 4, one method is to arrange multiple V-notches 106 as an easily openable structure on the surface of the packaging material, and place a band-shaped region 107 with a high concentration of microcapsules on the extension of the notches or in the region connecting the notches. The band-shaped region may be provided on the lower side (closer to the product side) of the aforementioned printed layer. Alternatively, the printed layer and the band-shaped region may be provided so as to be connected. The band-shaped region can be formed by applying microcapsules or a microcapsule-containing resin solution, or by a die coating method, etc.

[0029] Alternatively, a band-shaped area with a high concentration of microcapsules may be provided on the outer periphery (ends or sides) of the packaging material, extending from one or more notches or other easy-open structures, or in an area that is reliably torn when the packaging material is ripped. As an easy-open structure, laser cuts or perforations may be provided only on the very surface of the area with a high concentration of microcapsules to increase the area of ​​microcapsule exposure when the packaging material is opened. This ensures that when the user opens the product, the inside of the packaging material is reliably exposed to light, and the microcapsule-encapsulated area of ​​the cross-section of the packaging material is directly exposed, thereby more reliably initiating the decomposition of the microcapsule outer shell. Furthermore, if the decomposition-promoting substance is a microorganism, after the microcapsules disintegrate, the biodegradable resin, which serves as nutrients, comes into contact with the microorganism, and decomposition proceeds in a chain reaction. [Examples]

[0030] The following describes some examples. (Example 1) Microcapsules (10 μm in size) made of polymethyl methacrylate-styrene copolymer, containing actinomycetes of the genus Amycolatopsis as a decomposition-promoting substance and 0.5% by mass of benzophenone, were prepared. The obtained microcapsules were added at a concentration of 3% by mass to PLA (poly(L-lactide)), a biodegradable resin, to obtain a biodegradable resin composition. A film was processed using this biodegradable resin composition. The obtained film was manufactured into a gusseted bag 100 with side gussets, as shown in Figure 1, for use as a pillow bag for replaceable ink cartridges. As shown in Figure 1, the gusseted bag 100 has welded areas 101 at both ends and gussets 102 on the sides.

[0031] (Example 2) Microcapsules (15 μm in size) made of polyvinyl alcohol-methyl methacrylate copolymer containing 0.5% by mass of benzophenone and encapsulating Penicillium bacteria as a decomposition-promoting substance were prepared. The obtained microcapsules were added at a concentration of 3.0% by mass relative to the biodegradable resin PCL (poly(ε-caprolactone)). Microcapsules or a microcapsule-containing resin solution were pre-applied or sprayed onto the areas to be printed to create regions with a high concentration of microcapsules (4.5% by mass of microcapsules relative to the biodegradable resin) to obtain a biodegradable resin composition. A film was then processed using this biodegradable resin composition. Alternatively, multiple biodegradable resin compositions with different microcapsule concentrations may be formed into films simultaneously using an extrusion method equipped with multiple die heads. Furthermore, the film was provided with a printing area 103 containing printed information, a logo, etc., as shown in Figure 2, by inkjet printing. Furthermore, as shown in Figure 3, a region 105 with a high concentration of microcapsules was created on the underside (closer to the product side) of the surface layer with the printed layer 104 by a post-addition method of microcapsules. The total amount of microcapsules added was 4.5% by mass relative to the biodegradable resin composition. The resulting film was manufactured into a gusseted bag with side gussets, as shown in Figure 1, for use as a pillow bag for replaceable ink cartridges.

[0032] (Example 3) Microcapsules (20 μm in size) made of an ethylene-methacrylic acid copolymer containing 0.5% by mass of benzophenone and encapsulating actinomycetes of the genus Amycolatopsis as a decomposition-promoting substance were prepared. Using the obtained microcapsules and the biodegradable resin PBS (polybutylene succinate), 5.0% by mass of the microcapsules were added to the region 105 below the printed layer 104 in the same manner as in Example 2. In addition, 4.0% by mass of microcapsules relative to the biodegradable resin was added to the other regions. Furthermore, as shown in Figure 4, a band-shaped region 107 with a high concentration of microcapsules was formed in the area along the line connecting the V-notches 106 that are made after bag making, and the film was manufactured. This band-shaped region was also formed by coating or spray coating of microcapsules or a microcapsule-containing resin solution. This band-shaped region is located in the area below the printed area, closer to the product side, and is a region with a high concentration of microcapsules. The obtained film was manufactured into a gusseted bag with side gussets, as shown in Figure 4, to be used as a pillow bag for replaceable ink cartridges. Furthermore, as shown in Figure 4, a V-notch 106 was provided in the welded area 101.

[0033] In the gusset bags obtained in Examples 1-3, it was confirmed that the packaging material began to decompose after opening. [Explanation of symbols]

[0034] 100 gusseted bags with side gussets 105 Areas with high concentration of microcapsules

Claims

1. A packaging material containing a biodegradable resin and microcapsules containing a substance that promotes the degradation of the biodegradable resin, wherein the inside is light-shielded, and the microcapsules have an outer shell containing a photodegradable resin composition. A packaging material characterized by having an uneven concentration of the microcapsules within the packaging material.

2. The packaging material according to claim 1, wherein the substance that promotes the decomposition of the biodegradable resin is a microorganism capable of decomposing the biodegradable resin or an enzyme secreted by the microorganism.

3. The packaging material according to claim 1 or 2, wherein the photodegradable resin composition contains a resin having a photoexcitation structure selected from a carbonyl group or a carbon-carbon double bond.

4. The packaging material according to any one of claims 1 to 3, wherein the photodegradable resin composition contains a photodegrading agent or a resin having a photodegradable functional group.

5. The packaging material according to any one of claims 1 to 4, wherein the concentration of the microcapsules inside the packaging material is higher than the concentration of the microcapsules outside the packaging material.

6. The packaging material according to claim 5, wherein the packaging material has a printed layer on the outside, and below the printed layer, there is a region with a high concentration of the microcapsules.

7. The packaging material according to any one of claims 1 to 6, wherein the surface of the packaging material is provided with an easy-open portion, and the area around the easy-open portion has a high concentration of the microcapsules.

8. The packaging material according to any one of claims 1 to 6, wherein the outer circumference of the packaging material is provided with an easy-open portion, and the extension of the easy-open portion has a region with a high concentration of the microcapsules.

9. A packaging material according to any one of claims 1 to 8, for housing a replaceable ink cartridge.

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