JP2002112637A - Biodegradable raising seedling tray - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable raising seedling tray comprising a pulp mold excellent in strength/precision, and also easily decomposing after raising seedling. SOLUTION: This biodegradable raising seedling tray is obtained by molding a pulp mold produced by subjecting a pulp slurry containing a biodegradable resin to suction molding, and thereafter subjecting the molded resultant to hot pressing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seedling tray used for plant seedling or tissue culture, and more particularly to a biodegradable seedling tray made of a pulp mold obtained by suction-molding a pulp slurry.

[0002]

2. Description of the Related Art Generally, plastic seedling trays are used as trays, sheets or pots used for raising seedlings of plants, but there is a problem of disposal after use.

For example, as a tray using plastic, a suitable number of plastic seedling containers having flexibility and elasticity are arranged in the vertical and horizontal directions, and the upper edge of the opening of the adjacent seedling container is connected. The seedling container is provided with a dish that swells downward at the bottom, and the dish is swellable upward.
Japanese Patent No. 327507) has been proposed, but the use of plastics causes a large environmental burden when discarded.

[0004] Therefore, a tray made of a pulp mold obtained by suction-molding a pulp slurry has been developed. However, there are problems such as low strength. On the other hand, as a pulp mold having excellent strength and good dimensional accuracy, in a pulp mold manufactured by a wet suction molding method using pulp as a raw material, JAPAN T
APPI No. The water retention specified in 26-78 is 15
A pulp mold (JP-A-10-311000) characterized by containing fine fibers in the range of 0 to 500% has been proposed. The use of this pulp mold is not limited, but it is mainly used for packing materials and the like, and is not suggested to be used for trays for raising seedlings.

On the other hand, in a general pulp mold for raising seedlings and a method for producing the same, a tray for raising seedlings having high strength and high precision is imparted by mixing a hot-melt resin and performing hot pressing. No. 263978). However, there is no description of waste generated during production and use.

A method of raising seedlings by placing biodegradable plastic cells in a conventionally used plastic tray (Japanese Patent Application Laid-Open No. Hei 10-225235) and a non-biodegradable substance having a thin film on the surface of a biodegradable plastic product (Japanese Unexamined Patent Publication No. 11-227110) has been proposed. However, since biodegradable plastics are the main component, there is a problem that the material becomes quite expensive at this stage.

Further, biodegradable plastics 95 to 60
% By weight and 5 to 40% by weight of coconut shell (Japanese Patent Application Laid-Open No. 10-67876) and biodegradable by kneading 51 to 70% by weight of biodegradable resin and 30 to 49% by weight of paper powder. Material (Japanese Unexamined Patent Publication No. 10-323810)
Has been proposed. However, these also require three biodegradable resins.
There is a problem that it becomes a high-cost material because it is mixed more than a certain amount.

On the other hand, there has been proposed a biodegradable molded product obtained by thermally bonding the entire nonwoven fabric in which biodegradable fibers and cellulose fibers are mixed (Japanese Unexamined Patent Application Publication No. Hei 9-1997). 272760). However, it is considered that it is difficult to obtain a three-dimensional structure at the time of molding because the nonwoven fabric is mainly used.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above problems, and has an environmental load that is excellent in dimensional accuracy, maintains strength over a long period of use, and is easily decomposed after raising seedlings. It is an object of the present invention to provide a nursery tray comprising a small number of pulp molds.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that the strength and accuracy of the seedling raising tray are improved by hot pressing after molding the pulp mold. The present inventors have found that the strength and accuracy can be further improved by adding a biodegradable resin to the pulp slurry, and that the pulp slurry can be easily decomposed after raising seedlings, and the present invention has been completed.

That is, the present invention is as follows. (1) A seedling raising tray comprising a pulp mold obtained by suction-molding a pulp slurry containing a biodegradable resin, wherein the pulp mold is hot-pressed after molding. tray. (2) The biodegradable seedling tray according to (1), wherein the biodegradable resin is one or a mixture of two or more selected from an aliphatic polyester glycol-dicarboxylic acid polycondensation system, polylactides and polylactones. . (3) The biodegradable seedling tray according to (1) or (2), wherein the content of the biodegradable resin is 25% by mass or less based on the main raw material of the pulp slurry. (4) The biodegradable seedling raising tray according to any one of (1) to (3), wherein the pulp slurry contains a fungicide. (5) The biodegradable seedling raising tray according to any one of (1) to (4), wherein the pulp slurry contains a water repellent and / or a waterproofing agent.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The seedling raising tray of the present invention comprises a pulp mold obtained by suction-molding a pulp slurry containing a biodegradable resin,
It was hot pressed after molding.

The raw material of the pulp slurry is not particularly limited, and raw materials conventionally used in the production of pulp molds, for example, mechanical pulp, ground wood pulp, chemical pulp, soda pulp, waste paper pulp, dissolved pulp, ginned pulp ,
Synthetic pulp or the like can be used. In the present invention, waste paper such as newsprint, magazine, copy paper, or waste paper pulp obtained by defibrating corrugated cardboard or the like can be suitably used. Also, used paper or the like containing a heat-welding resin can be used.

The biodegradable resin used in the present invention includes natural polymers and synthetic polymers. Natural polymers that are biodegradable resins include cellulose, starch,
Plant-produced polysaccharides such as alginic acid; animal-produced polysaccharides such as chitin and hyaluronic acid; animal-produced proteins such as collagen and albumin; microorganism-produced polyesters such as poly (3-hydroxyalkanoate); microbial-produced polysaccharides such as hyaluronic acid; No.

Synthetic polymers that are biodegradable resins include:
Glycol / dicarboxylic acid polycondensation systems such as polyethylene succinate and polybutylene succinate; polylactides such as polyglycolic acid and polylactic acid; polylactones such as poly (ε-caprolactone); aliphatics such as polybutylene terephthalate adipate Examples include polyesters, polyols such as polyvinyl alcohol, polycarbonates such as polyester carbonate, polyanhydrides, polycyanoacrylates, polyorthoesters, polyphosphazenes, and the like.

Among these, polylactides (polyglycolic acid, polylactic acid, etc.) are more preferable. In particular, polylactic acid is obtained from starch and has a property of being decomposed into carbon dioxide and water even when discarded. Is preferably used.

The form of the biodegradable resin is not particularly limited, but a fibrous resin is usually used. The content of the biodegradable resin is 25% by mass or less, preferably 10 to 20% by mass, based on the main raw material of the pulp slurry. In addition, in this invention, "the main raw material of pulp slurry" contains the said biodegradable resin, mechanical pulp, groundwood pulp, waste paper pulp, etc. When a heat-welding resin is used, the heat-welding resin is also included in the main raw material.

Further, the pulp slurry may contain a fungicide. By including the fungicide, it is possible to prevent the growth of fungi such as mold while using the seedling raising tray.
The content of the fungicide is 10% of the main raw material of the pulp slurry.
Usually 5 parts by mass or less, preferably 0.1 part by mass with respect to 0 parts by mass.
5 to 3 parts by mass.

Further, the pulp slurry may contain a water repellent or a waterproofing agent or both of them. By including a water repellent or a waterproofing agent, deformation, destruction, and the like due to moisture absorption during use can be prevented. The total content of the water repellent or waterproofing agent is usually 5 parts by mass or less, preferably 0.5 to 5.0 parts by mass, based on 100 parts by mass of the main raw material of the pulp slurry.

Further, the pulp slurry may contain other additives such as a dry strength enhancer, a wet strength enhancer, a pH adjuster and the like, without departing from the spirit of the present invention. The content of these additives is usually 5 parts by mass or less, preferably 0.5 to 3 parts by mass, per 100 parts by mass of the main raw material of the pulp slurry.

The pulp slurry may contain a usual heat-weldable resin as long as the biodegradability of the seedling raising tray of the present invention due to the use of the biodegradable resin is not substantially impaired. The content of the heat-welding resin is preferably 25% by mass or less, more preferably 20% by mass or less, based on the main raw material of the pulp slurry.

The biodegradable seedling raising tray of the present invention is a seedling raising tray obtained by hot-pressing a pulp mold obtained by suction-molding a pulp slurry containing a biodegradable resin. Since it serves as a binder, strength and accuracy are improved.

The production of the seedling raising tray is performed, for example, as follows. A pulp slurry raw material containing waste paper or biodegradable plastic as a main raw material is defibrated in an aqueous solution, and various additives are added as needed to obtain a suspension. The solid content of this suspension is not particularly limited, but is 0.5 to 10% by mass,
Preferably it is 2-5 mass%. At this time, nutrients necessary for raising seedlings using the tray of the present invention may be added.

After the obtained suspension is transferred to a papermaking tank, water is added to lower the raw material concentration to about 2% by mass to obtain a pulp slurry. Using this, a pulp mold is obtained by suction molding using a mold. The shape of the mold is not particularly limited as long as it can be used as a tray for raising seedlings, such as a pot type or a sheet type.

Next, the pulp mold is sucked by a vacuum pump or the like to perform molding. Then, 8
The pulp mold is dried with hot air at 0 to 130 ° C. for 8 to 16 hours so that the moisture contained in the pulp mold is about 0 to 5% by mass.

Then, for about 24 hours in the room (temperature 20-30)
C. and a humidity of about 40 to 60% RH) to make the amount of water contained in the pulp mold constant. Subsequently, the pulp mold is hot-pressed. The temperature of the hot press is usually 100 to 300 ° C., preferably 150 to 200 ° C., and the pressure is usually 5 to 100 kg / cm ² , preferably 30 to 50 kg / c.
m ² and the time are usually 5 to 60 seconds, preferably 5 to 10 seconds.

The seedling raising tray of the present invention is usually a tray having a plurality of dishes for a large number of strains, but it can be divided and used for one strain. In addition, it can be cut for each plant after raising seedlings and used for subsequent work.

The seedling raising tray of the present invention can control the biodegradation period by the mixing ratio of the biodegradable resin in the pulp mold. By controlling the biodegradation period, the problem of disposal can be solved.

[0029]

The present invention will be described below more specifically with reference to examples and comparative examples. In each of Examples and Comparative Examples, unless otherwise specified, "raw material ratio" indicates the mass ratio of each raw material to the entire main raw material, and "additive ratio" indicates the mass ratio of the added amount to 100 mass parts of the entire main raw material. (Parts by mass) are shown. The additive ratio is not included in the raw material ratio.

[0030]

Example 1 Raw materials (used newspaper: 81% by mass, polylactic acid fiber (manufactured by Cargill): 19% by mass) were defibrated in an aqueous solution (4% by mass concentration) using a defibrating machine. Various additives shown in Table 2 were added, and after sufficient defibration, fixing was performed to obtain a suspension. After the suspension was transferred to a papermaking tank, water was added to reduce the concentration to 2% by mass and sufficiently dispersed to obtain a pulp slurry. Then, while the slurry is being stirred, a pulp mold raising mold dies having a length of 580 mm, a width of 280 mm, and a height of 64 mm are immersed in the slurry by a pulp mold forming machine, and the pulp slurry is formed by vacuum suction. After being stacked and adsorbed on the mold, the mold was pulled up from the slurry and inverted by 180 degrees. The shape of the pulp mold is 3.5 c long.
m, width 3.5cm, height 5.8cm (internal volume about 70cm
³ ) The cells are arranged in six rows vertically and twelve rows horizontally (total 72 cells) when viewed from above.

Further, while the pulp mold adsorbed in the laminated state is sucked upward, the mold for vacuum suction is then put on the pulp mold from above, and at the same time, the suction pressure of the molding die is reduced to zero. The pulp mold was transferred to the mold by applying pressure. Next, the pulp mold was removed from the mold and dried with hot air to prepare a pulp mold for seedling raising trays having a water content of 7% by mass and an average thickness of about 3 mm. The obtained pulp mold for raising seedling trays was left under a condition of 25 ° C. and 60% RH for 24 hours to control humidity.

The pulp mold for the above-mentioned dried seedling raising tray is sandwiched between inner and outer dies by using a mold (male mold, female mold) having a tray-shaped precision, and hot-pressed (200 ° C.,
40 kg / cm ² , 10 seconds) to produce a molded pulp mold for a nursery tray.

As Comparative Example 1, the used raw materials were newspaper waste paper:
81% by mass, PE (polyethylene) fiber (Product name: SW
P, manufactured by Mitsui Petrochemical Industry Co., Ltd.): 19% by mass), and a pulp molded article for a nursery tray was prepared in the same manner as described above.

Table 1 shows the main raw material composition of the pulp mold for raising seedling trays. The additives shown in Table 2 were used as the additives. An acrylic resin (manufactured by Arakawa Chemical Industries) was used as the drying strength enhancer, rosin (manufactured by Arakawa Chemical Industries) was used as the waterproofing agent, and polyolefin was used as the water repellent. A derivative (manufactured by Seiden Chemical Co., Ltd.), a bansulfate (manufactured by Oji Paper) as a pH adjuster, a polyamide resin (manufactured by Arakawa Chemical Industries) as a wetting enhancer, and an organic nitrogen-based compound (KAI) as a fungicide. Chemical Co.) was used.

[0035]

[Table 1]

[0036]

[Table 2]

As Comparative Example 2, a plastic tray made of a conventional PP (polypropylene) was used.
The following evaluation was performed on seedling raising trays.

<Biodegradation Test 1> JIS K was used to determine the biodegradability of the three samples of the pulp mold compact for seedling raising tray and the plastic tray prepared by the method described above.
The measurement was performed according to the aerobic biodegradation test method using 6950 plastic-activated sludge. For the degree of biodegradation, the remaining amount was calculated by the following equation.

[0039]

## EQU1 ## Degree of biodegradation = {(addition amount−remaining amount) / (addition amount)} × 100 (1)

Table 3 shows the results of biodegradation tests of two types of pulp mold trays (Comparative Example 1, Example 1) and a conventional plastic tray (Comparative Example 2). As is clear from this result, the plastic tray (Comparative Example 2) was not decomposed at all, but when the main raw material was pulp (Comparative Example 1), the decomposition rate was clearly high. Furthermore, when a biodegradable resin is used as a binder (Example 1)
Can be confirmed that the decomposition rate is rapidly increasing.

[0041]

[Table 3]

In the above test, the decomposition rate was remarkably confirmed because activated sludge was used. Further, it is considered preferable to conduct a field test when the device is left in ordinary soil.

<Biodegradation Test 2> The sample prepared above was buried in agricultural soil and the biodegradation rate was measured. The soil used was weighed after standing for 2 months in the Nisshinbo Research and Development Center field, and the degree of biodegradation was calculated using the above formula (1).

Table 4 shows pulp mold trays (Comparative Example 1,
The results of a biodegradation test of Example 1) and a conventional product (Comparative Example 2) are shown. As shown in Table 4, the seedling raising tray of the present invention showed excellent biodegradability.

[0045]

[Table 4]

<Strength Measurement Test> The strength of the prepared pulp mold for seedling raising tray (Example 1, Comparative Example 1) and the plastic tray (Comparative Example 2) were determined as “before raising seedling” and “after raising seedling” (raising period: 1 month). ) Was used to measure the strength.
A part of the side surface (50 mm in length and 10 mm in width) of each sample was taken as a sample, and a tensile tester (Instron 5) was used.
544; manufactured by Instron Japan). The measurement was performed at a crosshead speed of 5.0 mm / min, and the maximum stress Pa and the elastic modulus Pa at the yield point were measured. Table 5 shows the results.

As can be seen from the results, when pulp was used as a main raw material, a slight decrease in strength was observed after seedling raising (Example 1, Comparative Example 1), but the deterioration was not extreme.
There was no change in the strength of the plastic tray (Comparative Example 2). Thus, it was confirmed that the seedling raising tray of the present invention did not show any extreme deterioration during the seedling raising period.

[0048]

[Table 5]

[0049]

According to the present invention, it is possible to provide a biodegradable seedling raising tray which is excellent in strength and accuracy during use and is easily degraded after seedling raising.

Claims (5)

[Claims] 1. A nursery tray comprising a pulp mold obtained by suction-molding a pulp slurry containing a biodegradable resin, wherein the pulp mold is hot-pressed after molding. Sex seedling tray. 2. The biodegradable resin according to claim 1, wherein the biodegradable resin is one or a mixture of two or more selected from an aliphatic polyester glycol-dicarboxylic acid polycondensation system, polylactides and polylactones. Sex seedling tray. 3. The biodegradable seedling tray according to claim 1, wherein the content of the biodegradable resin is 25% by mass or less based on a main raw material of the pulp slurry. 4. The biodegradable seedling raising tray according to claim 1, wherein the pulp slurry contains a fungicide. 5. The biodegradable seedling raising tray according to claim 1, wherein the pulp slurry contains a water repellent and / or a waterproofing agent.