JP2006070178A - Biodegradable foam container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable foamed container having light weight, high strength on handling and less reduction of the strength during its use, quickly degrading on burying in the soil as it is, without inhibiting the growth of roots of seedlings and also easily decomposable on composting or microorganism-treating at the time of its disposal. <P>SOLUTION: This biodegradable container consisting of the biodegradable resin, preferably a resin composition containing an aliphatic polyester-based resin and an organized layered silicate is characterized by having 0.2-0.85 g/cm<SP>3</SP>density of the container. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a biodegradable foam container, and more specifically, it can be buried directly in the ground or can be recycled by a method such as thermal recycling, compost, biogas at the time of disposal, and has a biodegradation rate when buried in soil or treated with microorganisms. The present invention relates to a biodegradable foam container for growing trees and seedlings that is fast, lightweight, strong, and has heat insulation properties.

Conventionally, foamed styrene synthetic resins have been used as foam containers, but since these become waste after use, their treatment has been a problem. As an improvement method, one prepared by a material obtained by adding straw or the like to a foamed styrene synthetic resin is known (for example, see Patent Document 1). However, these materials can be recycled only by thermal recycling, and those that deteriorate or break down during use are likely to diffuse into the soil and contaminate the environment.
In addition, containers made of all biodegradable materials are also known in consideration of recyclability and environmental burden. For example, a vegetation pot made of biodegradable aliphatic polyester resin and paper powder, which can be transplanted into the soil as it is with a pot of seedlings (see, for example, Patent Document 2), rice husk and biodegradable plastic are heated and added. A container (see, for example, Patent Document 3) created by pressure pressing is known. These containers have good recyclability and can secure a certain degree of strength in terms of using plant materials and biodegradable resins. However, these containers are weak in handling and have the disadvantage that they are easily broken by impact when planting seedlings and handling, and also have the disadvantage that the strength is greatly reduced during use. Moreover, even if it is buried in the soil as it is, there is a problem that it is slow to decompose and may hinder the growth of seedling roots, and it is difficult to decompose when it is composted or treated with microorganisms at the time of disposal.
JP-A-8-143695 JP-A-10-323810 JP 2000-229312 A

  In view of the above problems, the present invention is light in weight, strong in handling, small in strength reduction during use, is quick to decompose even if buried in soil as it is, and does not inhibit the growth of seedling roots. An object of the present invention is to provide a biodegradable foam container that is easily decomposed when composting or microbial treatment at the time of disposal.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained a lightweight and lightweight container formed by foaming a resin composition containing a biodegradable resin and an organically modified layered silicate with carbon dioxide gas, etc. It becomes a biodegradable foam container with excellent mechanical properties such as strength during use, shape retention, thermal insulation, and degradability when buried in soil, and is particularly durable in normal use conditions. The present invention has been completed by finding that a foamed container that does not biodegrade during seedling growth and can be decomposed without problems after being embedded in soil.

That is, according to the first invention of the present invention, a biodegradable foam container comprising a resin composition containing a biodegradable resin and an organically modified layered silicate, wherein the density of the container is 0.2-0. A biodegradable foam container is provided, characterized in that it is .85 g / cm ³ .

  According to a second aspect of the present invention, there is provided a biodegradable foam container according to the first aspect, wherein the biodegradable resin is an aliphatic polyester resin.

  According to the third invention of the present invention, in the first or second invention, the compounding amount of the organically modified layered silicate is 0.01 to 5% by weight of the entire resin composition. A biodegradable foam container is provided.

The biodegradable foam container of the present invention comprises a resin composition containing a biodegradable resin and an organically modified layered silicate, and the density of the container is 0.2 to 0.85 g / cm ^3. The biodegradable foamed container is suitable for growing seedlings because it is lightweight and has no problems such as cracking during normal handling.

  The present invention is a biodegradable foam container obtained by foam-molding a resin composition containing an organically modified layered silicate in a biodegradable resin. Hereinafter, the present invention will be described in detail.

1. Biodegradable Resin Any biodegradable resin that can be foam-molded can be used as the biodegradable resin used in the foam container made of the biodegradable resin of the present invention. Examples thereof include aliphatic polyesters, polyamino acids, polyamide / polyester copolymers, polypeptides, celluloses, thermoplastic modified starches, and the like, and at least one resin selected from the group consisting of them or derivatives thereof.
Among these, particularly preferred are aliphatic polyesters such as polyglycolic acid, polylactic acid or copolymers of lactic acid with other hydroxyl carboxylic acids or mixtures thereof, poly (ε-caprolactone), polyethylene succinate, poly L-lactic acid copolymer which is a copolymer of tetramethylene succinate, poly-β-propiolactone, poly-β-butyrolactone, poly-γ-butyrolactone, polybutylene succinate (PBS) and other dicarboxylic acids ( PBSL), caproic acid copolymer (PBSCL), polybutylene succinate-carbonate, polybutylene succinate-adipate, and isothiocyanate cross-linked products of these aliphatic polyester resins or mixtures of these compounds, aliphatic polyester and polyamide copolymer polymerization It is used.
The biodegradable aliphatic polyester-based resin used in the present invention may be any one, but is preferably used for film grade, foam grade, or has a melt index (MI value) of 2 to 15. More preferably, a material exhibiting strain hardening is preferable.

  A cross-linking agent may be added to the biodegradable resin used in the present invention as long as the biodegradability is not impaired. The addition ratio of the crosslinking agent is preferably 5% or less, and if it is more than this, the biodegradability is lowered and the bubble growth of the foam is hindered. As the crosslinking agent, a polyvalent carboxylic acid, an isocyanate compound, an organic peroxide, an epoxy compound, a silane coupling agent, a metal complex, or a natural thermosetting component such as shellac or castor oil is used.

2. Organized layered silicate The layered silicate used in the present invention means a silicate mineral having exchangeable cations between layers, and usually has a thickness of about 1 nm and an average aspect ratio of about 20 to 200. Fine flaky crystals are aggregated by ionic bonds.
The type of layered silicate is not particularly limited, and examples include smectite clay minerals such as montmorillonite, saponite, hectorite, beidellite, stevensite, nontronite, vermiculite, halloysite, and swellable mica. Either natural or synthesized can be used.

  The organically modified layered silicate in the present invention is obtained by treating the above layered silicate with a cationic surfactant. Although it does not specifically limit as a cationic surfactant, A quaternary ammonium salt, a quaternary phosphonium salt, etc. are mentioned, Preferably the quaternary ammonium salt which has a C8 or more alkyl chain is used. When the alkyl chain having 8 or more carbon atoms is not contained, the hydrophilicity of the alkylammonium ion is strong and it becomes difficult to sufficiently depolarize the layer of the layered silicate, and biodegradable resin, particularly aliphatic polyester Dispersibility with the system biodegradable resin is lowered, and foamability is lowered.

  Examples of the quaternary ammonium salt include lauryl trimethyl ammonium salt, stearyl trimethyl ammonium salt, trioctyl ammonium salt, distearyl dimethyl ammonium salt (hereinafter sometimes abbreviated as DSDM), di-cured tallow dimethyl ammonium salt, di Examples include stearyl dibenzylammonium salt.

  Alternatively, silver ions may be coordinated between silicate layers. Further, in some cases, an organically modified layered silicate treated with a silane coupling agent or a titanate-based coupling agent may be used in order to improve adhesion to the biodegradable resin.

The content of the organically modified layered silicate used in the present invention is preferably 0.05 to 5% by weight, particularly preferably 0.5 to 3% by weight, based on the total amount of the resin composition. Degradability after soil embedding is good, and the content is 0.05 to 5% by weight from the viewpoint of degradability degradation at the stage of growing seedlings before embedding, strength retention, and foam expansion ratio (lightness) of the container Those are preferred.
When the organic layered silicate content is less than 0.05% by weight, the degradation rate of the biodegradable resin is the same as that of the biodegradable resin. However, it is fragile due to impact during handling. If it exceeds 5% by weight, the foamability at the time of container foam molding is greatly reduced, and the lightness cannot be secured. On the other hand, when the content is increased, the impact resistance of the container is extremely reduced, and the container is easily broken even during normal handling. There is a problem that the decomposition rate is greatly reduced after being buried in the soil.

3. Other components In this invention, you may mix a vegetable fiber as needed. For example, wood powders and fibers of cedar, cypress, pine, etc., bast fibers such as kenaf, jute, flax, ramie, cocoon of non-wood fibers, cotton, seed fibers such as kapok, manila hemp, sisal hemp, etc. Stem or leaf fibers, stem fibers such as palm fibers, fruit shell fibers such as palm fibers, and bamboo or straw fibers may be used singly or in combination. The content, the size of the fiber, and the like are preferably determined in accordance with the target strength and the degree of decomposition to such an extent that foamability is not lowered.

  Moreover, in order to adjust foamability and intensity | strength, you may use another natural inorganic component, for example, you may add a talc, a calcium carbonate, a calcium oxide, lime, shell pulverized materials, or these baked products. . In addition, clay minerals, granular silica compounds, titanium oxide, charcoal, zeolite compounds, diatomaceous earth, and those obtained by organic silane coupling treatment may be used. The amount added varies depending on the raw material and shape, but is preferably 10% by weight or less so as not to lower the foamability and decomposability.

  Furthermore, in order to adjust the degradability of the biodegradable resin, plant fibers that have been subjected to surface treatment such as plant fibers or acetylation treatment may be added. Moreover, you may add the cellulose acetate resin derived from a natural product, a modified starch, a polyamino acid resin, the copolymer of a polyamino acid and polyester, etc. as an adhesive improvement material.

4). Resin composition In the present invention, any method may be used as a method for producing a resin composition by mixing an organically modified layered silicate with a biodegradable resin. There are a method of foam molding using an injection foaming machine and a method of foam molding by directly introducing both into an injection foaming machine. In addition, when introducing an organic layered silicate into a kneader or direct injection molding device, a method of dry blending the biodegradable resin and the organic layered silicate in advance and then introducing the device into the device from a separate inlet There is a method of introducing and mixing.

5. Foaming container The biodegradable foaming container of the present invention may have any shape, and the shape is determined depending on the purpose of use. When used as a seedling pot, the diameter is about 5 to 20 cm and the height is about 5 to 30 cm. Cylindrical shapes such as mortar shapes and coffee cup shapes are generally applied. Any shape such as a container or a triangular pyramid may be used.
The wall thickness of the container is preferably 3 to 15 mm, which facilitates foam molding. Furthermore, a hole, a slit, etc. can be arbitrarily provided in the bottom part or side surface of the container. For example, when using it as a seedling pot, several holes and slits having a diameter of about 2 to 10 mm can be provided at the bottom. Also, several drain holes and slits can be arranged on the side surface.

The density of the foamed container of the present invention is preferably 0.2 to 0.85 g / cm ³ , more preferably 0.35 to 0.6 g / cm ³ . When the density of the container is less than 0.2 g / cm ³ , the strength of the container after seedling filling is insufficient, and the container is easily damaged during handling, and when it exceeds 0.85 g / cm ³ , there is a merit of lightness. Not only does not come out, but also the degradability of the container after being buried in the soil is lowered, and the air permeability is lowered, which causes the growth failure of the seedling.

  In the present invention, as a method for producing a biodegradable foam container, a known foam molding method can be applied. Any method of using a chemical foaming agent, a method of using a foaming gas, and a method of using both in combination. However, a chemical foaming agent is preferably used, and injection foam molding using carbon dioxide gas or a mixed gas of carbon dioxide gas and nitrogen gas, carbon dioxide gas and butane, or a low-volatile solvent is applied. A method of foaming only with carbon dioxide gas is particularly preferable.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the examples.

Example 1
Polybutylene succinate (GSPla manufactured by Mitsubishi Chemical Co., Ltd.) is used as a raw material biodegradable resin, and an organic layered silicate has a methyl group and a hydroxyethyl group, and an alkyl group having 18 or more carbon atoms. Montmorillonite cloicite 30B (manufactured by Nanocor) treated with a quaternary ammonium salt having 65% or more. The biodegradable resin and the organically modified layered silicate are mixed beforehand in a biaxial extruder so that the blending amount of the organically modified layered silicate is 0.5 wt%, and heated and melted at a barrel temperature of 150 ° C. A pellet having a diameter of about 3 mm was prepared. Next, the obtained pellets were introduced into an injection foam molding machine, and foamed and injected at an injection speed of 480 mm / s, a cylinder temperature of 170 ° C., a mold temperature of 40 ° C., a gas pressure of 7 MPa, and a gas injection amount of 3.5 wt%. A cylindrical foam container having a diameter of 70 mm, an opening diameter of 80 mm, a height of 120 mm, and a wall thickness of 6 mm was prepared. The density of the foamed container at this time was 0.53 g / cm ³ .
Next, 28 holes of 3mm diameter are opened at the bottom of the foam container, filled with vegetation soil (60% humus soil, 30% masa soil, 10% pumice), planted with ginseng, and grown outdoors for one month. The degree of seedling growth and the state of the bottom of the container were observed.
Further, a sample piece having a thickness of 6 mm, a width of 10 mm, and a length of 20 mm was cut out from the foamed container, and the biodegradability in standard soil was measured by a biodegradability test apparatus MODEA in accordance with the method of JIS K6953. At this time, the set temperature was 30 ° C., and the number of days when the decomposition rate was 20% was measured. The results are shown in Table 1.

(Example 2)
In Example 1, pellets were prepared so that the blended amount of the organically modified layered silicate was 3 wt%, the cylinder temperature during injection foaming was 180 ° C., and the gas injection amount was 3.2 wt%. Obtained. At this time, the density of the foamed container was 0.6 g / cm ³ . The results are shown in Table 1.

(Example 3)
In Example 1, the content of cloisite 93A, which is montmorillonite treated with a quaternary ammonium salt having a methyl group and having an alkyl group having 18 or more carbon atoms of 65% or more, is 3 wt% as the organically modified layered silicate. A foamed container was prepared using the above. The density of the foam container at this time was 0.75 g / cm ³ . The results are shown in Table 1.

(Comparative Example 1)
Using the same biodegradable resin and molding die as in Example 1, injection molding was performed at an injection speed of 480 mm / s, a cylinder temperature of 160 ° C., and a mold temperature of 40 ° C., a bottom diameter of 70 mm, an opening diameter of 80 mm, A cylindrical non-foamed container having a height of 120 mm and a wall thickness of 6 mm was prepared. The density of the container at this time was 1.25 g / cm ³ . The results are shown in Table 1.

(Comparative Example 2)
Using the same biodegradable resin and mold as in Example 1, the injection speed was 480 mm / s, the cylinder temperature was 160 ° C., the mold temperature was 40 ° C., the gas pressure was 7 MPa, and the gas injection amount was 3.5 wt%. A cylindrical foam container having a bottom diameter of 70 mm, an opening diameter of 80 mm, a height of 120 mm, and a wall thickness of 6 mm was prepared. The density of the foam container at this time was 0.48 g / cm ³ . The results are shown in Table 1.

(Comparative Example 3)
The same biodegradable resin and mold as in Example 1 were used, and 0.03 wt% of Closite 30B was blended as an organically modified layered silicate, injection speed 480 mm / s, cylinder temperature 165 ° C., mold temperature Foam injection was performed at 40 ° C., a gas pressure of 7 MPa, a gas injection amount of 3.5 wt%, and a cylindrical foam container having a bottom diameter of 70 mm, an opening diameter of 80 mm, a height of 120 mm, and a wall thickness of 6 mm was prepared. The density of the foam container at this time was 0.48 g / cm ³ . The results are shown in Table 1.

(Comparative Example 4)
In Example 1, pellets were prepared so that the compounding amount of closite 30B was 6 wt% as the organic layered silicate, the cylinder temperature at the time of injection foaming was 180 ° C., and the gas injection amount was 3.2 wt%. An injection foam container was obtained. At this time, the density of the foamed container was 1.03 g / cm ³ . The results are shown in Table 1.

  As can be seen from the results in Table 1, decomposition in the soil is promoted by foaming compared to a non-foaming container, but decomposition was suppressed by containing an organically modified layered silicate. In addition, there was no cracking during normal storage and seedling periods that were not embedded in soil, and normal handling was possible.

The biodegradable foam container of the present invention contains a biodegradable resin and an organically modified layered silicate, and the density of the container is 0.2 to 0.85 g / cm ^3. Since it is suppressed and is light and free from problems such as cracking during normal handling, it can be used for a long time as a seedling growth container in the case of using an environment with a lot of moisture and microorganisms, for example, compost. Furthermore, it has excellent heat insulation properties, is not easily affected by temperature changes during the night, and has a feature that seedlings are easy to grow stably.

Claims (3)

A biodegradable foam container comprising a resin composition containing a biodegradable resin and an organically modified layered silicate, wherein the density of the container is 0.2 to 0.85 g / cm ³ Degradable foam container.   The biodegradable foam container according to claim 1, wherein the biodegradable resin is an aliphatic polyester resin.   The biodegradable foamed container according to claim 1 or 2, wherein the amount of the organically modified layered silicate is 0.01 to 5% by weight of the entire resin composition.