JP5280331B2 - Nursery box sheet and method of using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a raising seedling box sheet having biodegradable properties, preservable for a long period, having a low production cost, hardly disjointing when taking out seedlings from a raising seedling box, and suppressed in entwinement around scraping tine of a rice transplanter. <P>SOLUTION: The raising seedling box sheet is arranged on the inner bottom of a raising seedling box. The raising seedling box sheet is a foaming sheet obtained by mixing 55-85 pts.wt. starch, 15-45 pts.wt. polylactic acid, and 0.5-5 pts.wt. foaming nucleating agent, adding water to the mixture followed by extrusion by an extruder 1 and foaming, and forming the product into a sheet-like form. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seedling box sheet and a method for using the same, and more particularly to a seedling box sheet disposed in a seedling box and a method for using the mat seedling for use in a rice transplanter.

  In Japan, the mechanization of rice cultivation has progressed, and the use of rice transplanters has become widespread for planting rice seedlings in rice fields. Rice transplanters hold seedlings with planting nails and insert them into the soil. The seedlings to be inserted include mat-shaped seedlings and pot-shaped seedlings. Matte seedlings are frequently used because they are easy to set and a large number of seedlings can be set.

  The mat-like seedlings are called a seedling box, placed in a shallow basin-shaped box with a width of about 30 cm, a length of about 60 cm, and a thickness of about 3 cm. And germinated.

  Usually, when the seedling is performed only with soil, there is a problem that if the seedling is removed from the nursery box, the seedling tends to fall apart and it is difficult to set it smoothly on the rice transplanter.

  For this reason, even if a water-permeable sheet is placed on the inner bottom of the nursery box, the roots of the seedling are grown so as to be entangled with the sheet, and even if the seedling is taken out from the nursery box, the seedling does not easily fall apart. ing.

  As an example of a seedling box sheet, as shown in Patent Document 1, a fiber pulp material is mixed with wood vinegar or bamboo vinegar and press-molded, or as shown in Patent Document 2, a cotton linter Non-woven fabric combining biodegradable fibers (cotton, short rayon fibers, polylactic acid short fibers, aliphatic polyester short fibers, etc.), as shown in Patent Document 3, biodegradable composite fibers (rayon, duracell, cotton) , Natural fibers such as wool or various pulps, polyethylene succinate, polybutylene succinate, polyglycolic acid, polylactic acid, poly (ε-caprolactone) and other aliphatic polyesters or copolyesters thereof, polyvinyl alcohol polymers, etc. Nonwoven fabrics containing 10% by mass or more of synthetic fibers) have been proposed.

  Further, as in Patent Document 4, an effective microorganism group (mainly photosynthetic bacteria, lactic acid bacteria, yeasts, actinomycetes) that uses a biodegradable polymer (corn starch) foam and contributes to plant growth in the foam. It has also been proposed to improve the biodegradability of mixed bacterial cells).

  However, the sheet of Patent Document 1 has a problem that the manufacturing process is complicated, biodegradability is slow, and fibers are easily entangled in a scraping claw of a rice transplanter that scrapes and seeds a seedling from a mat-like seedling. Moreover, in the nonwoven fabric using a biodegradable fiber like patent document 2 or 3, the coupling | bonding force between fibers is weak, and when taking out from a nursery box, it tends to fall apart. In order to prevent this, when the fiber is lengthened, there are problems such as being easily entangled with the scraper claw of the rice transplanter. In addition, these raw materials are expensive, and there is a problem that the cost of the sheet itself is increased.

  In the foam using the corn starch of Patent Document 4, the foam itself is brittle, and when the moisture is absorbed, the bonding strength of the sheet is reduced, and the sheet is separated. In addition, there is a problem that it is difficult to store for a long time because of its high water absorption.

Japanese Patent No. 3811802 JP 2001-64862 A JP 2002-209460 A JP-A-8-205673 JP 2004-168991 A JP 2003-145604 A

  The problems to be solved by the present invention are to solve the above-mentioned problems, have biodegradability, can be stored for a long period of time, have a low production cost, and fall apart when the seedling is taken out from the nursery box. It is an object of the present invention to provide a seedling box sheet and a method of using the same, which are less likely to become entangled and also prevent entanglement of the scraper claws of the rice transplanter.

In order to solve the above problems, the invention according to claim 1 is a sheet placed on the inner bottom of a nursery box, wherein starch is 55 to 85 parts by weight, polylactic acid is 15 to 45 parts by weight, and foaming nucleating agent were mixed in a ratio of 0.5 to 5 parts by weight, water to extrusion foaming in the addition extruder, Ri foamable sheet der formed into a sheet, the expansion ratio of the sheet is 20 to 40 times This is a seedling box sheet.

  The invention according to claim 2 is the seedling box sheet according to claim 1, wherein the starch is corn starch, and the foaming nucleating agent is either talc or calcium carbonate.

  The invention according to claim 3 is the seedling box sheet according to claim 1 or 2, wherein the sheet is used in a seedling box for growing mat-like seedlings of rice used in a rice transplanter. .

  According to a fourth aspect of the present invention, the seedling box sheet according to any one of the first to third aspects is disposed on the inner bottom of the seedling box, floor soil and straw are disposed on the sheet, This is a method for using a seedling box sheet characterized by growing mat-like seedlings of rice to be used.

  The invention according to claim 1 is a foam containing 55 to 85 parts by weight of starch, so that an increase in raw material costs and manufacturing costs can be suppressed, and a highly biodegradable sheet can be obtained. In addition, by blending 15 to 45 parts by weight of polylactic acid, the brittleness of the starch foam during water absorption is improved and long-term storage is possible while maintaining biodegradability.

  In addition, by adjusting the blending ratio of starch and polylactic acid as in the present invention, it is possible to effectively suppress the fibers from getting tangled in the scraper claw of the rice transplanter. Moreover, since the melting point of polylactic acid is sufficiently higher than 100 ° C., it is possible to form sufficient foaming by extrusion water foaming.

  Furthermore, by containing 0.5 to 5 parts by weight of the foaming nucleating agent, a finely textured foam can be obtained, the mechanical strength of the sheet itself is increased, and the seedlings are also removed when the seedlings are taken out from the nursery box. It becomes difficult to fall apart.

  According to the invention according to claim 2, by using corn starch as starch, and using either talc or calcium carbonate as a foaming nucleating agent, raw materials can be easily obtained, and the cost is low. An excellent seedling box sheet can be provided.

  According to the invention according to claim 3, since the seedling box sheet is used in a seedling box for growing mat-like seedlings of rice used in the rice transplanter, when the seedling is taken out from the seedling box and set in the rice transplanter, However, when the seedling is scraped off from the mat-like seedling, the fiber of the sheet is not entangled with the scraping nail.

  A mat-like seedling of rice used in a rice transplanter, wherein the sheet for a seedling box according to any one of claims 1 to 3 is disposed on the inner bottom of the seedling box, floor soil and straw are disposed on the sheet. It is possible to grow mat-like seedlings suitable for rice transplanters.

It is the schematic which shows a mode that the sheet | seat for seedling boxes of this invention is manufactured. It is a figure explaining the shape of the sizing die used with the manufacturing apparatus of FIG.

Hereinafter, the seedling box sheet of the present invention will be described in detail using preferred examples.
The seedling box sheet of the present invention is a sheet placed on the inner bottom of the seedling box, and includes 55 to 85 parts by weight of starch, 15 to 45 parts by weight of polylactic acid, and 0.5 to 5 parts of foaming nucleating agent. were mixed at a ratio of parts by weight, water to extrusion foaming at addition extruder, Ri foamable sheet der formed into a sheet, the expansion ratio of the sheet is characterized in that 20 to 40 times.

  In particular, the seedling box sheet of the present invention is preferably used in a seedling box for growing mat-like seedlings of rice used in a rice transplanter.

  As the starch used in the seedling box sheet of the present invention, corn starch, wheat starch, rice starch, legume starch, potato starch, tapioca starch and the like can be used. Most preferred is corn starch, which is readily available and inexpensive. In the present invention, 55 to 85 parts by weight of starch is used. This is because starch, in particular corn starch, is relatively cheaper than the raw materials disclosed in Patent Documents 1 to 3, and the foam of the present invention is manufactured more than the nonwoven fabrics of Patent Documents 1 to 3. This is because a uniform sheet can be produced continuously and in large quantities. Furthermore, starch has a higher biodegradability than natural fibers such as pulp, and is less likely to be entangled in the scraper claws of rice transplanters.

  However, with only starch, the foam sheet is fragile. In particular, due to the characteristics of starch, it tends to become tattered during water absorption, and long-term storage is difficult. At the time of storage, it is necessary to maintain a dry state, and handling becomes complicated. For this reason, although it is preferable to mix a synthetic resin with a raw material, in polymers, such as polyolefin resin, there exists a problem that a biodegradability falls and a fiber becomes easy to get involved in the scraping nail | claw of a rice transplanter. In addition, polymers such as polybutylene succinate have a low melting point, and there is a problem that a sufficient foam sheet cannot be obtained when mixing with corn starch and performing extrusion water foaming.

  Polylactic acid is suitable as a material for solving these problems, and the melting point is relatively high at about 170 ° C. The blending ratio of starch and polylactic acid can suppress the raw material cost and increase the biodegradability by containing more than half, preferably 55 to 85 parts by weight of starch. The amount of polylactic acid is 15 to 45 parts by weight. If the amount of polylactic acid is excessive, it takes time for biodegradation, and the resin is easily entangled with the scraping claws of the rice transplanter. On the other hand, when the content of polylactic acid is small, the mechanical strength of the foam sheet cannot be improved, and the sheet becomes brittle against moisture.

  In the seedling box sheet of the present invention, it is preferable to contain 0.5 to 5 parts by weight of a foaming nucleating agent that serves as a core during foaming in order to perform extrusion water foaming. As the nucleating agent for foaming, talc or calcium carbonate can be suitably used. Other inorganic powders and organic powders can be used. It is also possible to use plant-derived materials such as waste paper powder and rice husk powder. By including such a foaming nucleating agent, a finely textured foam can be obtained. Such a foam sheet has high mechanical strength of the sheet itself, and it is difficult for seedlings to fall apart even when the seedlings are taken out from the nursery box.

  As a raw material for the seedling box sheet of the present invention, a plant-derived material having biodegradability can be added in addition to those described above. For example, various things such as plant nuts, leaves, stems / stems, and skins can be used, and these are added to other materials while leaving powders or fibers. However, when the plant fiber remains, it is preferable to cut and use the fiber so as not to get entangled with the scraper claw of the rice transplanter.

  In addition to the materials described above, the seedling box sheet of the present invention can be mixed with various materials such as fertilizers and biodegradable microorganisms in order to increase the added value of the sheet. Moreover, the mixing timing may be at the time of forming the foam sheet, or may be added after the sheet is formed.

  In the method for using the seedling box sheet of the present invention, the sheet of the present invention is arranged on the inner bottom of the seedling box, and the floor soil and the straw are arranged on the sheet, similarly to the conventional sheet. By sprinkling the entire seedling box or immersing the seedling box itself, watering is performed to grow the seedling. At the time of rice transplanting, the seedling (mat-like seedling) is taken out from the seedling box together with the sheet and set on the rice transplanter. The rice transplanter scrapes the seedlings sequentially from the mat-like seedlings and plantes them in the rice field.

  Since the seedling box sheet is disposed on the inner bottom of the seedling box, the thickness of the sheet is 1 cm or less, preferably 0.5 cm or less. Since it is necessary to arrange floor soil on the arranged sheet, when the thickness of the sheet increases, the conventional nursery box (depth of about 3 cm) cannot be used, and the thickness of the mat-like seedling including the sheet This is because there is a possibility that it cannot be set on the rice transplanter itself. Further, when the thickness of the sheet is increased, the sheet is easily entangled with the scraping claws of the rice transplanter, and problems such as the inability to scrape the appropriate number of seedlings are likely to occur.

Next, the manufacturing method of the seedling box sheet | seat of this invention is demonstrated with FIG.
Reference numeral 1 denotes a twin-screw or single-screw extruder, and corn starch, polylactic acid, talc and the like are separately or premixed from a hopper 2. While all the raw materials are being charged and mixed, about 10% by weight of water is supplied by the supply means 3 with respect to the total weight of the raw materials. Corn starch usually contains about 12 to 13% by weight of water. In this manufacturing method, in order to promote foaming of the mixture, the water is further added to cause foaming.

  The raw material containing water is heated to about 170 to 180 ° C. and extruded from the extruder 1. At this time, the material is foamed by heated steam to form a foam. Since the foam is formed into a sheet, a sizing die 4 is disposed at the outlet of the extruder 1 to generate a foam having a rectangular cross section. For these manufacturing methods, the technique disclosed in Patent Document 5 or 6 can be suitably used.

  As shown in FIG. 2A, the sizing die 4 has a shape in which a rectangular parallelepiped portion 41 having a hollow inside and a plate 42 in which a large number of pores are formed are coupled. On the extruder side of the sizing die 4 (arrow B in FIG. 2A), as shown in FIG. 2B, a large number of pores 44 having a diameter of about 2 mm are formed. Moreover, the rectangular opening 43 is formed in the exit side (arrow C of Fig.2 (a)) of the sizing die 4 like FIG.2 (c). The rectangular size depends on the size of the sheet to be formed, but is about 30 cm wide and 1 cm high.

  By using a sizing die as shown in FIG. 2, the material exiting the extruder 1 exits the pore 44, rapidly expands in the internal space of the rectangular parallelepiped 41, opens the shape while adjusting the shape within the rectangular parallelepiped. 43 is pushed out.

  In order to continuously pull out the foam 10 pushed out from the sizing die 4 in the direction of arrow A, the foam is fed out by the roller 5. The roller 5 needs to be sandwiched to such an extent that the foam can be conveyed. However, as in Patent Document 4, if the sheet is compressed using the roller 5, the fiber density on the surface of the sheet (the density of the foam material) tends to be high, the biodegradability is deteriorated, and the rice transplanter scrapes off. There arises a problem that the sheet material is easily entangled with the nails.

  The expansion ratio of the sheet is about 20 to 40 times, and about 25 to 35 times can be suitably used. As described above, in the present invention, it is not preferable to compress the sheet. However, if the sheet needs to be compressed, the final foaming ratio after compression is about 20 to 40 times. Thus, it is preferable to set the expansion ratio to a high value in advance.

  The foam sheet that has passed through the roller 5 is further transported by another roller 6, and the foam sheet is cooled with air in the course of transport. Finally, the sheet is cut to an appropriate length and accumulated in a laminated state.

  In order to reduce the space occupied by the sheet in the nursery box and to secure a space for the floor soil, the thickness of the seedling box sheet is preferably 1 cm or less, preferably 0.5 cm or less as described above. In order to set the thickness of the foam sheet to these conditions, a method of setting the height of the rectangular opening 43 of the sizing die 4 in the range of 1 cm to 0.5 cm, or forming a thick foam sheet, There is a method of cutting into slices and setting the thickness within a predetermined range.

  As described above, according to the present invention, it has biodegradability, can be stored for a long period of time, is low in manufacturing cost, and is less likely to fall apart when taking out seedlings from a nursery box. It is possible to provide a seedling box sheet that suppresses the entanglement of the scraping nails.

DESCRIPTION OF SYMBOLS 1 Extruder 2 Hopper 3 Water supply means 4 Sizing die 5, 6 Roller 10 Foam

Claims (4)

A sheet placed on the inner bottom of a nursery box, in which starch is mixed in an amount of 55 to 85 parts by weight, polylactic acid in an amount of 15 to 45 parts by weight, and a foaming nucleating agent in a ratio of 0.5 to 5 parts by weight. was added was extruded foamed extruder, Ri foamable sheet der formed into a sheet, nursery box sheet, wherein the expansion ratio of the sheet is 20 to 40 times.   The seedling box sheet according to claim 1, wherein the starch is corn starch, and the foaming nucleating agent is either talc or calcium carbonate.   The seedling box sheet according to claim 1 or 2, wherein the sheet is used in a seedling box for growing mat-like seedlings of rice used in a rice transplanter.   A seedling box sheet according to any one of claims 1 to 3 is placed on the inner bottom of the seedling box, floor soil and straw are placed on the sheet, and a mat-like seedling of rice used in a rice transplanter is provided. A method of using a seedling box sheet characterized by nurturing.

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