JPH01199523A - Plant seedling-raising bed and production thereof - Google Patents

Abstract

PURPOSE:To provide a plant seeding-raising bed having good durability and hydrophilic property, by mixing inorganic and/or organic granules, the aqueous solution of a specific binder and a crosslinking agent, compression-molding the mixture, drying the molded product to a dry state and heat-treating the dried product. CONSTITUTION:A mixture of inorganic and/or organic granules (zeolite, peat moss, etc.), the aqueous solution of a binder (polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, polyacrylamide or acrylate salt) and a mono- and/or di-aldehyde crosslinking agent is compression-molded. The molded product is dried until moisture does not substantially exist therein (until the water content thereof is reduced to <=6%) and heated at >=100 deg.C to cause homogeneously self crosslinking thereof.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a plant nursery bed and a method for producing the same.

[Prior Art] Recently, in order to rationalize agricultural and horticultural work, promote plant growth, and increase the yield of agricultural products, a method has been adopted in which seedlings are grown in a nursery and then transplanted to a field. Generally, seedlings are raised by sowing them in bed soil or pots filled with potting soil, watering them, covering them with soil, watering them again, and growing them until they are suitable for transplanting after germination, and then dividing the grown seedlings or removing them from the pots and transplanting them.

However, in this transplanting process, the rooting soil mass tends to collapse during transportation and transplanting of the grown seedlings, resulting in damage to the roots and failure of transplantation, resulting in poor rooting after planting.

This phenomenon is particularly noticeable in plants with roots without root hairs.

In addition, in recent years, with the rationalization of agricultural work, transplanting has become more mechanized and automatic transplanters and special seedling raising boxes are being developed. It is necessary to find a way to maintain it.

Various proposals have been made to meet these demands, and it has become common practice to harden the soil with a binder. Requirements for such binders and seedling beds hardened using binders include: (1) the soil must be at least 15 to
It must have sufficient cohesive strength in a moist state with 25% water (2) It must not hinder the germination and growth of plants (3) It must not be washed away by rainfall or irrigation during the seedling-raising period (4) ) Contains no harmful substances that may contaminate the soil, such as heavy metals or harmful ions. (5) The soil must have appropriate hydrophilic properties so that it does not become water repellent. (6) It hinders plant germination and growth. (7) It is inexpensive.

[Problems to be Solved by the Invention] Various attempts have been made to meet these requirements.

For example, Japanese Patent Application Laid-Open No. 59-59119 proposes a method of improving the hardness of seedling cultivation soil for transplanting using polyacrylamide or polyacrylamide copolymer, but the binder used in this technique is Since it remains essentially water-soluble even after sterilization and heat treatment to adjust moisture, the binding agent is washed out by watering during the seedling-raising period, making it impossible to maintain its strength until transplanting. ,
Additional auxiliary tools such as pots and bowls are required for reinforcement.

In addition, a method for producing a nursery bed in which inorganic materials such as glass fibers, ceramic fibers, and rock wool are molded into a mat-like aggregate using phenolic resin, and the phenolic resin is heated to form a monument, was published in JP-A-H.
It is disclosed in the publication No.-141217. In this technology, it has been shown that in addition to phenolic resins, urea resins, vinyl acetate resins, and acrylic ester resins can also be used as binders. If such a binder is used, the resin will certainly become insoluble in water after drying and hardening, so the strength of the seedling bed will be maintained sufficiently during sowing, watering, and transplanting, but the drawback is that the resin after hardening is hydrophilic. This results in poor irrigation and poor irrigation efficiency, which hinders germination and seedling growth. Although it has been proposed to use a surfactant in combination for the purpose of improving hydrophilicity, it is not sufficient in terms of effectiveness and sustainability of hydrophilicity.

On the other hand, as another method for creating water-resistant seedling beds, JP-A No. 80-23838 discloses intermolecular crosslinking by combining a maleic anhydride copolymer and a trivalent or higher metal compound. A method has been proposed to wake it up. This bam,
Hydrochlorides and sulfates of iron and aluminum are used as metal compounds, but these salts remain in the soil even after transplantation and are not favorable for plant growth. In addition, this type of metal crosslinked product sometimes becomes water repellent and requires the addition of a surfactant.

Another method that has been proposed for creating hardening seedbeds is a method using modified polyvinyl alcohol having a silyl group in the molecule as a binder, as disclosed in Japanese Patent Application Laid-open No. 59.
It is disclosed in Japanese Patent No.-183630. In this case,
The modified polyvinyl alcohol used causes a chemical reaction with the soil and crosslinks and hardens, creating a strong bond, resulting in water resistance and
It has sufficient durability and is also moderately hydrophilic, making it desirable as a seedling bed, but the disadvantage is that the modified polyvinyl alcohol itself is expensive, and its binder There are problems with long-term storage stability.

Furthermore, water-soluble polymers such as polyvinyl alcohol, sodium polyacrylate, starch, methylcellulose, carboxymethylcellulose, gelatin, casein, and sodium alginate are used as binders for forming seedling beds.
It is also known to use a molded product obtained by mixing various granules and molding and then drying until there is virtually no moisture as a seedling bed, but none of them are strong enough and require watering until transplanting. It lacks the durability to withstand.

[Means for Solving the Problems] The present invention has been made by focusing on such conventional problems, and after drying a specific selected water-soluble polymer, it is dried in the presence of a specific crosslinking agent. By treating the material under specific temperature conditions, the material is uniformly self-crosslinked, thereby providing a durable and hydrophilic seedling bed at a low cost.

That is, the present invention comprises: an inorganic and/or organic particulate material, polyvinyl alcohol, carboxymethyl cellulose,
An aqueous solution of at least one binder selected from the group consisting of methylcellulose, hydroxyethylcellulose, polyacrylamide, and acrylates and a crosslinking agent consisting of mono- and/or sealaldehyde are mixed, compression molded, and then substantially water-free. The present invention relates to a method for manufacturing a plant nursery bed, which is dried until it is no longer present, and then heat-treated at 100°C or higher, and a plant nursery bed obtained by the manufacturing method.

[Function] The present invention uses a self-crosslinking water-soluble polymer as a binder, and compression molds a mixture of this, a crosslinking agent, and inorganic and/or organic particulates (hereinafter referred to as inorganic (organic) particulates). After that, dry the molded product until it is substantially free of moisture.
It is characterized by heat treatment at 00°C or higher.

The specific self-crosslinking water-soluble polymer used in the present invention is
It has the property of self-crosslinking only when heated to 110° C. or higher in the absence of substantial moisture, and becoming irreversibly water-insoluble.

Therefore, even without using a cross-linking agent, a seedbed with excellent durability and water resistance can be obtained by sufficiently heating. However, for this purpose, a large amount of heat must be applied, and since it relies only on self-crosslinking, the degree of crosslinking changes greatly depending on variations in heating conditions, and the resulting products tend to vary.

In the present invention, by adding a specific crosslinking agent, such variations due to self-crosslinking can be eliminated, and the heating temperature can be lowered to improve economic efficiency.

In addition, in the present invention, as mentioned above, it is important to first dry the material thoroughly. However, as mentioned above, the conventional drying process is stopped in a state where water is substantially absent, and self-crosslinking does not proceed, making it impossible to obtain a material with sufficient strength. In the present invention, a state in which substantially no water is present refers to a state in which the water content is 6% or less.

[Preferred Embodiment] The self-crosslinking water-soluble polymer used as a binder in the present invention is at least one selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, polyacrylamide, and acrylate. . The molecular weight is 30,000~
5,000,000, preferably 100,000 to 2,000,000; if it is less than 30,000, crosslinking will be insufficient and the desired strength and water resistance cannot be achieved. If it exceeds 5 million, it becomes an aqueous solution and becomes difficult to handle. Examples of polyvinyl alcohol include completely or partially saponified products of polyvinyl acetate, and carboxy-modified products. In addition to acrylamide homopolymers, polyacrylamides include (meth)acrylic acid or its salts, unsaturated carboxylic acids or their salts such as maleic acid or its salts, vinylsulfonic acid or its salts, styrenesulfonic acid or its salts, etc. unsaturated sulfonic acids or their salts, methacrylamide, nonionic unsaturated monomers such as hydroxyethyl acrylate, tertiary nitrogen-containing monomers such as dimethylaminoethyl (meth)acrylate, (meth)acryloyloxyalkyl A copolymer of a quaternary nitrogen-containing monomer such as trialkylammonium is used. In addition, examples of polyacrylates include monovalent metal salts such as Li, Nu, and K; ammonium salts and amine salts such as ammonia, triethanolamine, trimethylamine, and triethylamine; among these, those that are preferably used are , Na', K, are ammonium salts.

Furthermore, copolymers of various unsaturated monomers exemplified by acrylamide and acrylic acid may also be used.

The water-soluble binder particularly preferably used in the present invention is
polyvinyl alcohol, carboxymethylcellulose,
These are methylcellulose, hydroxyethylcellulose, and polyacrylamide.

As the crosslinking agent for the water-soluble polymer, monoaldehyde, dialdehyde, or both thereof may be used. As the mono- or di-aldehyde, a compound having one or two aldehyde groups in one molecule and soluble or dispersible in water is selected, such as formaldehyde, acetaldehyde, propionaldehyde, glyoxal, malonaldehyde, Examples include succinic aldehyde and glutaraldehyde. Compounds that regenerate aldehydes by heating or the action of acids, such as paraformaldehyde and acetal, can also be used in the present invention. Particularly preferably used aldehydes include formaldehyde, glyoxal, and glutaraldehyde, all of which are preferably used in the form of an aqueous solution.

The inorganic (organic) granules to be mixed with the water-soluble binder may be those commonly used for seedling raising and gardening. Examples of the inorganic granules include zeolite, bentonite, perlite,
Examples include vermiculite, clay, gypsum, slag, Kanuma soil, mountain soil, field soil, sand, diatomaceous earth, whitebait balloons, etc. Organic granules include peat moss, wood flour, rice husk, rice husk fumigated charcoal, water-absorbing synthetic resin powder, etc. can be mentioned, but
It is not limited to these. Moreover, the inorganic particulate matter and the organic particulate matter may be blended individually or in combination. The particle size of these inorganic (organic) particles is preferably 10 mesh passes or less and 100 mesh passes or more. (2) When the mesh pass is larger than 0, it is difficult to mix uniformly, and when the mesh pass is smaller than 100, when mixed with the binder, lumps are likely to occur due to secondary aggregation.

In the present invention, first, an aqueous solution of a water-soluble polymer, a crosslinking agent, and an inorganic (organic) particulate material are mixed. At that time, the concentration of the aqueous solution of the water-soluble polymer varies depending on the molecular weight, amount of binder used, etc., but is usually 2 to 20% (wt%, same hereinafter),
The content is preferably 3 to 15%. When used at a high concentration of more than 20%, the entire inorganic (organic) particulate matter cannot be covered, and the resulting seedling bed becomes heterogeneous in strength. On the other hand, if it is diluted more than 2%, a large amount of heat will be required during subsequent drying, which is not preferable. In addition, the viscosity of the aqueous solution (25°C) is 20 to 10,000 cP,
Preferably it is in the range of 50 to 5000 cP.

The amount of the binder to be blended is 0.2 to 15 parts, preferably 1 to 8 parts by dry weight, per 100 parts (by weight, hereinafter the same) of the inorganic (organic) granules. If it is less than 0.2 parts, the strength and durability of the seedbed will be insufficient, and if it exceeds 15 parts, the strength will be too high and root growth may be inhibited.

The amount of crosslinking agent is 0.5 of the dry solid content of the water-soluble binder.
-20%, preferably 2-10%. 0.5
If it is less than %, crosslinking will be insufficient and the desired water resistance will not be achieved. If the seedling bed exceeds 20%, it becomes too hard.
It has a negative effect on the rooting and growth of the target. Further, it is suitable for mixing that the crosslinking agent is added in the form of an aqueous solution.

The concentration is usually 10-70%, preferably 20-50%.
%.

In addition, the binder used in the present invention has the property of self-crosslinking and becoming irreversibly water-insoluble as described above when heated in a state substantially free of moisture. In addition to crosslinking, it is also effective to add acidic substances such as formic acid, acetic acid, citric acid, glycolic acid, and malic acid to promote self-crosslinking. Among these, acetic acid is particularly preferably used.

By adding these acidic substances, the heat treatment time can be shortened,
Furthermore, economical advantages such as a reduction in heating temperature can be realized. The amount of the self-crosslinking accelerator added is 5 to 30 parts per 100 parts (dry weight) of the binder.

Mixing of an inorganic (organic) particulate material, an aqueous binder solution, and a crosslinking agent is carried out by adding an aqueous binder solution, an aqueous crosslinking agent solution, and, if necessary, an additive such as a self-crosslinking accelerator to the inorganic (organic) particulate material, usually at room temperature. Below is a V-type mixer, ribbon mixer,
Mix evenly with a mixer such as a wet ash machine.

This mixture is then compression molded. In compression molding, the homogeneous mixture is filled into a seedling bed mold of a desired shape and uniaxially compressed from above. Although the degree of compression depends on the particle size of the inorganic (organic) particulates, it is appropriate to compress the homogeneous mixture to 60 to 80% by volume of the original volume. Compression molding that can be obtained ・The strength of the object (-axial compressive strength) is usually 0.1 kg/
It is preferable to set it to CD or more.

It is possible to eject the compression-molded product as it is from the hole in the lower part of the mold using an ejector pin, but if you do this when the moisture content is too high, the strength of the molded product itself will be weak and it will collapse. Therefore, it is desirable to perform primary drying until the moisture content is about 2 to 6% or less before releasing from the mold. In this case, workability is improved if a silicone-based mold release agent is applied to the inner surface of the mold in advance. Although some crosslinking occurred during the secondary drying, it did not reach the level of strength required for growing seedbeds.

In the present invention, it is important to dry the compression molded product until it is substantially free of moisture before heating it at 100° C. or higher.

Such drying may be performed within the compression mold as described above, or may be performed after release from the mold. It is also primarily dried in the mold,
It may be dried again after demolding.

For drying, use a hot air dryer, a ventilation dryer, etc., and dry until substantially no moisture is present.

The suitable drying conditions are usually 90 to 100°C for 1 to 3 hours. In addition, you may air-dry.

The molded product thus obtained, which does not contain substantially any water, is
Heat treatment at temperatures above 0°C causes the binder to self-crosslink, giving the molded product the necessary strength and water resistance. The heat treatment is performed at a temperature of 100°C or higher using, for example, a hot air heating machine or a heating oven.
The heating is carried out for at least 2 hours, preferably at 105° C. or higher for 2 hours or more. Although there are no particular upper limits for temperature and time, for economic reasons, heat treatment at 140° C. for more than 3 hours is meaningless. During this heat treatment, the water-soluble binder and the crosslinking agent react and crosslinking progresses, at the same time self-crosslinking of the water-soluble binder occurs, imparting water resistance to the seedling bed and sterilizing it at the same time. Note that this heat treatment step may be performed continuously to the drying step. In addition, heat treatment does not necessarily have to be carried out at a constant temperature; the crosslinking reaction is initially kept at a relatively low temperature to prevent volatilization of the crosslinking agent, and then heated to a high temperature in the latter half to remove excess crosslinking agent and accelerator. A method of removing by volatilization is also effective.

As a result of the crosslinking of the binder, the plant nursery bed obtained by the production method of the present invention has sufficient strength and water resistance to withstand watering and transplanting, and also has appropriate hydrophilicity.

The seedbed of the present invention can have any shape and size, and may be appropriately selected depending on the size and shape of the seeds of the target plant and the transplanter. Preferred shapes include, for example, truncated cones, discs, rectangular trapezoids, cubes, and rectangular parallelepipeds, and each of these may be an independent nursery bed, or a plate-like shape with a cut in part. It may also be a partially continuous structure such as a molding machine. Further, their strength (-axial compressive strength) is preferably in the range of 2 to 5 kg/cJ.

Seedlings are raised by sowing the seeds on the seedbed or in a depression provided therein and watering the seedlings.

For transplanting, this nursery bed should be transplanted together with the seedlings. After transplanting, the nursery bed of the present invention gradually collapses and is assimilated into the soil, so it does not affect the growth of the plants.

Next, the present invention will be explained based on examples, but the present invention is not limited only to these examples.

Example 1 Polyvinyl alcohol with a degree of polymerization of about 500 and a hydrolysis rate of 88% (Gohsenol GL-05 manufactured by Nippon Gosei Kagaku Kogyo ■)
) was dissolved in water under heating (80-90°C) to prepare a 10% aqueous solution. Add this polyvinyl alcohol 1 to a V-type mixer.
65 parts of a 0% aqueous solution, 2 parts of a 25% aqueous solution of glutaraldehyde, 0.3 part of acetic acid, and 100 parts (430 parts by volume) of Ube Perlite Type 2 (manufactured by Ube Industries ■) were charged and mixed uniformly.

A silicone-based mold release agent was applied in advance to the inner surface of an iron mold in which a number of female molds, each having an ejection hole at the bottom and an upper diameter of 30 ml, a lower diameter of 25 mm, and a height of 25 nu++ were arranged, and then the above mixture was applied. Filled. Using a male mold from the top, the filling was compressed to approximately 70% of its original volume to form a seedling bed.

Place the mold filled with the molded material into a hot air circulation dryer and heat it at 100°C for 2 hours until the moisture content of the molded material in the seedling bed reaches 3.
%.

After this dry product was cooled, it was lightly extruded through the protrusion hole at the bottom to take out the dried molded product, which was then placed in an oven and heat-treated at 110° C. for 2 hours to produce a seedling bed of the present invention.

In order to examine the mechanical strength of the seedbeds, 100 seedbeds were allowed to fall naturally from a height of 1 m onto oak boards 10m thick, and none of them collapsed.

Comparative Example 1 When a seedling bed was prepared in the same manner as in Example 1 except that the glutaraldehyde aqueous solution was not added and subjected to a drop test, 5I out of 100 collapsed.

Examples 2 to 8 The polyvinyl alcohol, crosslinking agent, and perlite used in Example 1 were replaced with binders, crosslinking agents, and inorganic granules or organic granules or mixtures thereof listed in Table 1. A seedling bed was prepared by the same treatment as in Example 1.

The results of the drop test are shown in Table 2.

[Margins below] Table 2 Test Examples The center part of the upper part of the seedling beds obtained in Examples 1 to 8 of the present invention and Comparative Example 1 was cut to a diameter of approximately 511II11.
A depression of 3 cm deep was made, and Komatsuna seeds were sown and watered every - day to germinate and raise seedlings. As a control, seeds were also sown in alluvial soil (alluvial soil for plugs).

In all seedling beds, water absorption, germination, and growth conditions during irrigation were good. 14 days after sowing, the seedlings, which had grown to about 3cm mouthparts, were planted in the field.

At the time of transplantation, the seedbeds of Examples 1 to 8 did not collapse and could be transplanted as they were, but the seedbed of Comparative Example 1 collapsed and some root breakage occurred during transplantation. On the other hand, when seedlings grown in alluvial soil were transplanted, the soil around the roots collapsed, resulting in root breakage.

[Effects of the Invention] The plant nursery bed of the present invention does not require auxiliary tools such as pots and pots, has water resistance that can withstand watering during the seedling raising period, and has the strength to maintain its shape even when transplanted. Moreover, it maintains appropriate hydrophilicity, does not inhibit the germination and growth of seeds, and does not contain any harmful substances that may have an adverse effect on the soil, making it extremely useful. Furthermore, according to the production method of the present invention, the seedling bed can be homogeneously grown using inexpensive materials in a simple manner in a short time and at low energy costs, and at the same time, a sterilization effect can be achieved. It can also be used as a sterile medium support for plant tissue culture.

Patent applicant: Daiichi Kogyo Seiyaku Co., Ltd. Takii Seed Co., Ltd.

Claims (1)

[Scope of Claims] 1. An inorganic and/or organic particulate material, at least one aqueous solution selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, polyacrylamide, and polyacrylate, and mono- 1. A method for producing a plant nursery bed, which comprises mixing a crosslinking agent consisting of and/or di-aldehyde, compression molding, drying until substantially no moisture is present, and then heat-treating at 100° C. or higher. 2. A plant nursery obtained by the manufacturing method according to claim 1.