JP2002153138A - Biodegradable sheet material for forming nursery block - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable sheet which is a sheet material suitable for wrapping culture soil, forming a continuous cylindrical material, cutting the continuous cylindrical material and producing a nursery block of a short cylindrical body, having heat-sealability and easy cutting properties in addition to air and water permeabilities and moisture-resistant strength and capable of retaining the shape during a nursery period but degrading in soil. SOLUTION: This degradable sheet material for forming the nursery block is characterized by compounding staple fibers of biodegradable thermoplastic synthetic fibers with papermaking fibers and polyvinyl alcohol staple fibers, providing a papermaking raw material, adding a wet strengthening agent thereto, preparing a blend paper, impregnating or coating the resultant blend paper with a biodegradable thermoplastic resin and regulating the air permeability to >=10,000 cu, the wet tensile strength to >=0.14 kN/M and the bending stiffness to >=30 mN.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable sheet material used for forming cultivated soil for raising plants such as vegetables and flowers into a seedling raising block.

[0002]

2. Description of the Related Art In recent years, for cultivation of vegetables, flowers and the like, a method has been widely adopted in which seedlings are grown in a seedling container for a certain period of time and then replanted in a field, planting place or pot. For this purpose, seedling raising boxes, seedling raising pots, seedling raising trays, and the like are generally used. These containers are filled with cultivation soil to form seedling raising blocks, and seeds such as vegetables and flowers are placed in the seedling raising blocks. Seedlings are germinated or cut and seedlings are raised. After growing for a certain period after germination or after cutting, the seedling raising block is taken out of the seedling raising container and transplanted into a field or a pot. Not only is excessive labor involved in root excision work, but also the labor and costs involved in collecting, moving, and disposing of seedling containers that are no longer needed after transplantation.

[0003] For this reason, a seedling pot formed of a biodegradable non-woven fabric which decomposes in soil has been proposed so that cultivated plants can be transplanted into soil without the need for replanting work, while keeping the plant in the seedling pot. (JP-A-6-81259,
JP-A-6-113682, JP-A-9-37653,
No. 37654, JP-A-9-205895, etc.). Seedling pots molded from such a biodegradable nonwoven fabric,
There is no problem of root damage due to root cutting, etc., and the problem of removing seedling blocks from the seedling containers and disposal of used seedling containers is also resolved, but the process of individually molding seedling pots from biodegradable nonwoven fabric It is also necessary to fill the cultivation soil for each seedling pot. There is also known a method of enclosing cultivated soil in a nursery paper cylinder to form a cultivated soil-enclosed paper cylinder (Japanese Patent Laid-Open No. 9-308386, etc.). I do.

[0004] As a method for further simplifying these steps and operations, a method has been proposed in which a cultivated soil is wrapped with a biodegradable sheet material having air permeability and water permeability to form a cylindrical seedling raising block (JP-A-Hei. No. 9-154405). An example disclosed in JP-A-9-154405 is a cylindrical nursery block having a diameter of 3 to 4 cm and a length of 4 to 6 cm. In this cylindrical seedling raising block, a continuous sheet for seedling raising molding having a width equal to the circumferential length of the cylindrical body plus a joining portion (glue margin) of about 1 cm is continuously formed into a long cylindrical shape. It is manufactured by filling the inside of the cylindrical body with the cultivated soil in a suction manner and cutting the cylindrical continuous body filled with the cultivated soil into an appropriate length with a saw blade or the like. For example, Patent No. 276
No. 3959, "Method and apparatus for producing a block from a soft material such as sphagnum moss" by using an apparatus as disclosed in a tubular continuous body formed of a biodegradable sheet, It can be formed by cutting into an appropriate length to form a short cylindrical body. Also,
For example, in an apparatus using the principle of a cigarette manufacturing machine,
It can be manufactured by forming a cylinder of desired diameter and length larger than a cigarette.

That is, as shown in FIG. 1, a continuous tubular body 3 in which a cultivated soil 2 is wrapped with a biodegradable sheet material 1 is manufactured, and this is cut into an appropriate length, and as shown in FIG. A short tubular seedling raising block 4 is used. After each short tubular seedling block, the seedlings are germinated or cut, and then seedlings are raised. After raising the seedling, the biodegradable sheet 1 wound on the outer periphery can be transplanted to a field or a pot without removing it. Such a tubular seedling raising block does not have a separate molding step as in a seedling raising pot formed of a conventional biodegradable nonwoven fabric, and the operation of filling soil for each pot can be omitted.

However, what is disclosed as a biodegradable sheet material in JP-A-9-154405 is as follows.
Polyethylene resin for adhesion is sprayed on natural paper.Because polyethylene is difficult to decompose, it retains its original sheet form even after being buried in soil for several years. When cultivating the soil, it is entangled with the farm equipment and the plow part of the cultivator, which is a major obstacle to agricultural work.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a sheet material suitable for forming a tubular seedling raising block as described above, which retains the sheet form during the seedling raising. However, it is an object of the present invention to provide a biodegradable sheet material in soil that takes about 2 to 4 months to collapse into a sheet form and about 1 to 2 years to complete decomposition.

[0008] In addition to having air permeability, water permeability, and moisture resistance, the sheet material for forming the tubular seedling raising block has the following properties.
It is necessary to have an easy cutting property for cutting a continuous cylindrical body into a short cylindrical body with a saw-like shape. Since the biodegradable nonwoven fabric is usually made of a relatively long fiber biodegradable fiber and is flexible, the biodegradable nonwoven fabric, when wrapped in a biodegradable nonwoven fabric to form a continuous tubular body, Even when cutting into a short cylindrical body, the fibers of the non-woven fabric are entangled with the saw teeth and cannot be easily cut. In light of these circumstances,
The present invention has been made to provide a biodegradable sheet having rigidity that is easily cut by employing a papermaking method using short fibers as a raw material. In addition, when an adhesive is used for joining when wrapping the soil and forming it into a continuous tubular body, the joint portion will lose the air permeability and water permeability of the sheet, so a sheet having heat sealing adhesive properties Consideration was also given to the fact that joining can be performed by heat sealing without impairing air permeability and water permeability.

[0009]

According to the present invention, there is provided a blending method comprising blending short fibers of biodegradable thermoplastic synthetic fibers, fibers for papermaking and short fibers of polyvinyl alcohol as a raw material for papermaking, and adding a wet strength enhancer. A papermaking impregnated or coated with a biodegradable thermoplastic resin to have a permeability of 10,000 cu or more, a wet tensile strength of 0.14 kN / M or more, and a bending stiffness of 30 mN or more. It relates to a degradable sheet material.

The sheet material for forming a seedling-growing block according to the present invention is suitably used for forming a continuous tubular body by wrapping the cultivated soil as described above and cutting it into a seedling-growing block having a short tubular shape. it can.

[0011] When raising seedlings, air permeability is required, and the sheet for forming a seedling raising block is manufactured so as to have an air permeability of 10,000 cu (cholester unit) or more. If the air permeability is less than 10,000 cu, the voids between the fibers of the molding sheet are small, the roots cannot penetrate the paper layer during the seedling raising, grow in the bottom direction along the molding sheet, and swirl at the bottom. The growth after transplanting the seedling block becomes poor because of the root-roll state.

[0012] The sheet for forming a seedling raising block must have a wet tensile strength of 0.14 kN / m or more.
If it is less than this, the sheet is easily torn when it is moistened by irrigation, and the soil collapses when picking up the nursery block, making transplantation impossible.

Further, according to an experiment, it has been found that the sheet material for forming a seedling-growing block requires a bending stiffness of 30 mN or more in order to easily cut a continuous cylindrical body with saw teeth. If the bending stiffness is less than this, the sheet is torn when cut with a saw tooth, or the cut edge is broken, so that a clean cylindrical shape is not obtained. When cutting a continuous sheet, the bending stiffness of the sheet needs to be within the above range in the vertical direction in contact with the saw tooth at right angles.

In the present invention, in order to obtain a rigid sheet having good cutting properties, a method of forming a base material by means of mixing papermaking raw materials made of short fibers instead of a nonwoven fabric is employed. In the present invention, a biodegradable thermoplastic synthetic fiber is used as a raw material for papermaking in order to obtain heat sealability, moisture resistance, and air permeability. In addition, polyvinyl alcohol short fibers are blended and blended for improving the bending rigidity. In order to improve the cutability of the sheet, short fibers are used as the papermaking raw material. These papermaking raw materials are all biodegradable substances, but it is necessary to maintain a certain level of moisture resistance without biodegradation during the seedling raising period before transplantation in soil. Therefore, a wet strength enhancer is added to compensate for the decrease in wet resistance due to the incorporation of the papermaking fiber, and the mixed paper is impregnated or coated with a biodegradable thermoplastic resin to cover the papermaking fiber. Slow down the decomposition rate. Impregnation or coating of a biodegradable thermoplastic resin also serves to reinforce heat sealability.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The blending ratio of short fibers of biodegradable thermoplastic synthetic fibers, fibers for papermaking and short fibers of polyvinyl alcohol to be blended in mixed paper is 30 to 95:60 to 4:
It is desirably 1 to 10. The biodegradable thermoplastic synthetic fiber short fiber is a biodegradable thermoplastic resin melt-spun and cut to a certain length, having a fineness of 0.2 to 10 d (denier) and a fiber length of 1 to 20 mm. Is desirable. If the fineness is less than 0.2 d, the paper layer of the mixed paper is too dense, and the air permeability of the sheet after coating and impregnating the biodegradable thermoplastic resin on the mixed paper does not reach 10,000 cu. .
If the fineness exceeds 10d, the number of biodegradable thermoplastic synthetic fibers in the mixed paper is reduced, and the strength is undesirably reduced. If the fiber length is less than 1 mm, the strength of the mixed paper is reduced, and if it is more than 20 mm, the synthetic fibers are twisted or entangled at the time of papermaking, and the papermaking property is undesirably reduced.

The biodegradable thermoplastic resin used for melt spinning includes polybutylene succinate (melting point 114 ° C.),
Polyethylene succinate (melting point 100 ° C), polybutylene succinate adipate (melting point 96 ° C), poly 1
-Lactic acid (melting point 175 ° C), poly d, l-lactic acid (melting point 12
0 ° C.), polycaprolactone (melting point 60 ° C.), polybutylene succinate carbonate (melting point 106 ° C.) and the like. These single component fibers may be used alone, or two or more single component fibers may be used in combination.
In addition, a conjugate fiber composed of two or more types of components may be used in advance, and the conjugate fiber may have a sheath-core structure in which the core portion and the sheath portion are composed of different components. The sheath-core type composite fiber uses a biodegradable thermoplastic resin having a melting point of 90 to 120 ° C. for the sheath, and the core component has a melting point of 20 to 30 ° C. more than the sheath component.
By using a high biodegradable thermoplastic resin, it is possible to heat and fuse the sheath component of the fibers while maintaining the fiber form on the dryer of the paper machine, thereby improving the papermaking properties and increasing the strength of the mixed papermaking. There are advantages. As such a sheath-core type composite fiber, a sheath portion is a combination of polybutylene succinate adipate, a core portion is a combination of polybutylene succinate, a sheath portion is a combination of poly d, l-lactic acid, and a core portion is a combination of poly l-lactic acid, A combination of a poly-l-lactic acid / polycaprolactone copolymer having a sheath portion and a poly-l-lactic acid having a core portion is known.

The biodegradable thermoplastic synthetic fiber is preferably blended at 30 to 95% by mass in the papermaking raw material, and the blending ratio is 3%.
When the amount is less than 0% by mass, the heat sealing strength is insufficient, and it is difficult to heat seal and join the joining portions of the cylinders in the cylinder manufacturing apparatus. Further, when the blending ratio is less than 30% by mass, the permeability of the mixed paper is reduced, and it is difficult to achieve a permeability of 10,000 cu after impregnating or coating the biodegradable thermoplastic resin. On the other hand, the biodegradable thermoplastic synthetic fiber content was 9%.
When the content exceeds 5% by mass, when the biodegradable thermoplastic synthetic fibers are heat-fused together on a dryer of a paper machine, the mixed paper does not easily peel off from the surface of the dryer, and the papermaking property is deteriorated.

[0018] The papermaking fiber blended in the mixed paper is used to reduce the cost by reducing the blending ratio of expensive biodegradable thermoplastic synthetic fiber, and is used for softwood bleached kraft pulp, hardwood bleached kraft pulp, mercerized pulp. Wood pulp such as dissolved pulp and curled fiber pulp, non-wood pulp such as flax pulp, manila hemp pulp and kenaf pulp, semi-synthetic fiber such as rayon staple fiber, and purified cellulose fiber such as lyocell staple fiber are used. Of these papermaking fibers, natural fibers such as wood pulp and non-wood pulp are beaten and used in the range of 500 to 700 ml CSF, and the type and beating degree of the natural fibers are appropriately selected according to the air permeability of the mixed paper. . For example, to increase both the air permeability and the sheet strength, use Manila hemp pulp beaten to about 500 ml CSF.
A technique such as using softwood bleached mercerized pulp beaten to about mlCSF is used.

The fiber length of the papermaking fiber is preferably 0.8 mm to 5.0 mm as a weight-weighted average fiber length. Those having a short weight-weighted average fiber length are hardwood pulp, and those having not been beaten exhibit a weight-weighted average fiber length of about 1 mm. On the other hand, those having a long weight-weighted average fiber length are flax pulp, and those having a too long weight are used after being cut to 5 mm or less by beating treatment. The papermaking fiber is blended mainly for cost reduction, but without blending, the strength of the wet paper at the time of papermaking is weak, the paper is easily cut, and it is difficult to peel off from the surface of the dryer. As a countermeasure against this, it is necessary to incorporate at least 4% by mass of the papermaking fiber into the papermaking raw material.

The polyvinyl alcohol short fibers to be mixed with the mixed paper are used when the wet paper is dried by a drier, and are used to firmly bond the constituent fibers of the mixed paper after drying to increase the drying strength and rigidity. As a result, there is also an effect of improving the cutting property when cutting the continuous cylindrical body filled with the cultivated soil with saw teeth. As the polyvinyl alcohol short fibers, generally available polyvinyl alcohol short fibers for papermaking having a dissolution temperature of 60 to 80 ° C and a fiber length of 3 to 5 mm can be used, and the blending ratio is appropriately 1 to 10% by mass of the papermaking raw material. It is. When the mixing ratio is less than 1% by mass, the effect of improving the dry strength and the bending stiffness is insufficient, while the mixing ratio is 10%.
If the amount is more than 10% by mass, the mixed paper is less likely to be peeled off from the surface of the dryer of the paper machine at the time of papermaking, and the papermaking property is undesirably reduced.

A mixed paper made of biodegradable thermoplastic synthetic fibers, papermaking fibers, and polyvinyl alcohol short fibers has a high wet strength of bonding between the biodegradable thermoplastic synthetic fibers, but has a high wet strength. The bonding between fibers for fibers and polyvinyl alcohol short fibers has low wet strength (wet resistance),
There is a disadvantage that it is broken by irrigation during the seedling raising period before biodegradation. To compensate for the lack of wet strength, a wet strength enhancer is added. The addition amount of the wet strength enhancer is 0.1 to 5% by mass as a solid content with respect to 100% by mass of the fiber component.
To be added. Polyamide polyamine epichlorohydrin resin, melamine formaldehyde resin, urea formaldehyde resin,
And cationic starch fatty acid ester emulsions. If the addition amount is less than 0.1% by mass, the effect of improving the wet strength is insufficient, and if it exceeds 5% by mass, the effect of improving the wet strength level off compared to the increase in the cost of the wet strength enhancer, which is not preferable. The method of adding the wet strength enhancer is carried out by adding to the papermaking raw material, that is, a method of so-called internal addition, or a method of impregnating and coating with a size press device in a papermaking process.

For the production of the mixed paper, existing paper machines such as a short net paper machine, an inclined short net paper machine, a circular net paper machine, and a circular net / short net combination paper machine can be used. In particular, it is preferable to use an inclined short-mesh paper machine because the papermaking becomes easy even when the fiber length is 10 mm or more.

The basis weight of the mixed paper is preferably 20 to 40 g / m ^{2. If} the basis weight is lower than 20 g / m ² , the strength is insufficient, and if the basis weight exceeds 40 g / m ² , the air permeability decreases. The composition of the mixed paper is such that short fibers of biodegradable thermoplastic synthetic fibers, papermaking fibers, and polyvinyl alcohol short fibers have a mass ratio of 30 to 9%.
In addition to a single-layer structure composed of one kind of papermaking raw material blended at a ratio of 5:60 to 4: 1 to 10, the outermost layer of the sheet has a multilayer structure to increase the blending ratio of the biodegradable thermoplastic synthetic fiber,
The intermediate layer may have a lower blending ratio of the biodegradable thermoplastic synthetic fiber than the outermost layer.

The reason why the mixed paper is coated or impregnated with the biodegradable thermoplastic resin is to further increase the wet strength of the mixed paper.
Also, it is for covering the papermaking fiber which is easily biodegradable to delay the biodegradation during the seedling raising period. As the biodegradable thermoplastic resin used for coating or impregnation, cellulose acetate, ethyl cellulose, shellac, polybutylene succinate,
Examples thereof include polybutylene succinate adipate, polylactic acid, and polycaprolactone, which are used in the form of a solution dissolved in acetone, toluene, a halogenated hydrocarbon solvent, or an oil-in-water emulsion.

Furthermore, polyvinyl alcohol having a degree of saponification of 8 to 60 mol% is mentioned as a biodegradable thermoplastic resin which forms a water-resistant film and is also desirable in terms of heat sealability. Polyvinyl alcohol having a saponification degree of 8 to 60 mol% swells in cold water but does not dissolve, so that the papermaking fiber can be coated with a water-resistant film without adding a water-proofing agent. Further, since polyvinyl alcohol having a saponification degree of 8 to 60 mol% has thermoplasticity, it can be reinforced as necessary without impairing the heat sealing property of the base material-mixed paper. The preferred range of the degree of saponification of polyvinyl alcohol is 15 to 45 mol%, more preferably 20 to 30 mol%.

The polyvinyl alcohol having a saponification degree of 8 to 60 mol% is used after being dissolved in a mixed solvent of alcohol and water, a mixed solvent of ketone and water, or a halogenated hydrocarbon solvent. As the alcohol, methyl alcohol, ethyl alcohol, and isopropyl alcohol are preferable, and as the ketone, acetone is used. The mixing ratio of these organic solvents and water depends on the alcohol or ketone:
Water = 40 to 90:60 to 10, preferably alcohol to ketone: water = 60 to 80:40 to 20. Examples of the halogenated hydrocarbon solvent include trichloroethylene, dichloromethane, dichloroethane and the like.

The lower the degree of saponification, the lower the biodegradability of polyvinyl alcohol. If the degree of saponification of polyvinyl alcohol is less than 8 mol%, the biodegradability is insufficient for use in impregnation or coating in the present invention. . In addition, the degree of saponification is 60
As a result of experiments, it is difficult to increase the wet strength of polyvinyl alcohol of more than 95 mol% and less than 95 mol% even when impregnated and coated on mixed paper, and water-proofing agents such as polyamide polyamine epichlorohydrin resin are blended. However, the effect of improving the wet strength of the mixed paper is hardly observed.

On the other hand, polyvinyl alcohol having a saponification degree of 95 mol% or more can be used because it is soluble in hot water but insoluble in cold water. However, since water resistance alone is insufficient, a water-resistant agent is mixed and used in the form of an aqueous solution. As the water-proofing agent, a polyamide polyamine epichlorohydrin resin, a melamine formaldehyde resin or the like is blended and used in a known ratio. The polyvinyl alcohol having a saponification degree of 95 mol% or more may be modified by introducing a carboxyl group.

The above biodegradable thermoplastic resins may be used alone or in combination of two or more. Since all of the above biodegradable thermoplastic resins have a lower biodegradation rate than papermaking fibers, by coating or impregnating the mixed paper to cover the surface of the papermaking fibers, the seedlings can be grown before being transplanted into soil. The collapse of the seedling-forming block forming sheet due to biodegradation during the period can be suppressed. The rate of biodegradation in soil depends on the type of biodegradable thermoplastic resin, and by selecting or combining the type of biodegradable thermoplastic resin to be applied or impregnated from the above biodegradable thermoplastic resins. The biodegradation rate of the seedling raising block forming sheet can be adjusted.

As described above, the sheet for raising seedling blocks obtained by coating or impregnating the biodegradable thermoplastic resin on the mixed paper has a permeability of 10,000 cu or more and a wet tensile strength (wet resistance). It is necessary that the strength be 0.14 kN / m or more. The air permeability and wet strength of the sheet for forming a seedling raising block can be adjusted by adjusting the amount of the biodegradable thermoplastic resin adhered to the base mixed paper. If the amount of the biodegradable thermoplastic resin is less than 1 g / m ² , the air permeability increases, but the wet tensile strength does not reach 0.14 kN / m, while if the amount of the biodegradable thermoplastic resin exceeds 10 g / m ² , Although the wet tensile strength increases, the air permeability becomes insufficient because the air permeability does not reach 10,000 cu. For this reason, the solid content adhesion amount of the biodegradable thermoplastic resin must be 1 to 10 g / m ² .

The biodegradable thermoplastic resin to be coated or impregnated on the mixed paper itself has heat sealing properties, but when the solid content is in the range of 1 to 10 g / m ² , sufficient heat sealing properties are not obtained. I can't get it. In order to impart heat-sealing properties to the seedling block forming sheet, it is essential to mix biodegradable thermoplastic synthetic fibers into the mixed paper used as the base material. The thermoplastic resin plays a role in reinforcing the heat sealing property of the base mixed paper.

As a method of coating or impregnating the biodegradable thermoplastic resin on the mixed paper, an existing coating and impregnating method such as a mangle, a size press, a roll coater, and a gravure coater can be used. Moreover, you may spray by a spray method.

The sheet material for forming a seedling-growing block according to the present invention is obtained by forming a continuous tubular body having a diameter of 20 to 80 mm by wrapping the cultivated soil, cutting the same into a height of 1 to 1.5 times the diameter,
It can be suitably used as a seedling block of a short cylindrical body having a height of 30 to 120 mm, but the wrapping type of the cultivated soil is not necessarily limited to the cylindrical body, and it may be a prismatic body, or may be an individual bag shape. It is also possible to use.

[0034]

The following test methods are commonly used in the following Examples and Comparative Examples.

Method for Evaluating Heat Sealability and Cuttability in Manufacture of Cylindrical Body The basic structure is the same as that of a cylindrical molding machine (manufactured by Elegard) having the structure described in Japanese Patent No. 276959, A cylinder molding machine remodeled so as to be suitable for the production of a body nursery block was prepared. FIG. 3 is a cross-sectional view for explaining the cylinder molding machine. This cylinder molding machine has a diameter of 4c.
m to produce a cylinder block of 4 cm in length, width 1
A winding 6 of a cylindrical body forming sheet 5 having a length of 32 mm and a length of 1400 m is mounted. This cylinder molding machine has a heat sealing section,
It consists of the main components of the filling section and cutting section.

In the heat sealing portion A, the cylindrical body is molded and heat sealed. A tubular body forming sheet 5 is wrapped around a pipe 8 for supplying the cultivation soil 7, formed into a cylindrical shape, and a margin portion (approximately 6 mm) is superimposed, and lowered by a working cylinder (not shown) at regular time intervals. The above-mentioned glue margin portion is thermally sealed by a rectangular parallelepiped heating block 9 having a width of 5 mm and a length of 120 mm. The open state (a1) and the heat sealing state (a2) are repeated by the vertical movement of the heating block.

In the filling section B, the soil is filled inside the cylinder by intermittent suction. The pipe 8 extends halfway inside the suction chamber 10 in which the pipe 8 can be clamped, and the suction chamber 10 has a cylindrical hollow portion 11 having the same diameter as the pipe. A large number of suction holes are provided on the contact surface so that the inside of the cylinder can be sucked through the cylinder forming sheet. The suction chamber 10 can be divided vertically into two parts in a horizontal plane, and can alternately repeat vertical division and vertical integration, and perform a reciprocating motion of moving forward and backward a fixed length (4 cm) in the horizontal direction. In the closed suction state (b
1), the closed advance state (b2), and the open reverse state (b3) are repeated.

At the cutting portion C, the cylindrical body is cut by saw teeth. The cylindrical continuous body filled with the cultivation soil 7 is sent to the cutting chamber 12, attached at an angle of 60 degrees with respect to the horizontal plane, and moved up and down by a working cylinder (not shown).
As a result, the cylindrical block 14 is obtained by cutting at regular intervals (4 cm). The sawtooth rising state (c1) and the cutting state (c2) are repeated.

The combination of the operation states of the heat sealing section A, the filling section B, and the cutting section C is as follows.
-C1, the second step is a1-b2-c1, the third step is a1-b3-c2, and these three steps are repeated.

The heat-sealing property and the cutting property of the sheet for forming a cylindrical body were evaluated as follows. At the mounting position of the cylinder molding machine,
A cylinder-forming sheet to be tested was attached, filled with seedling cultivation soil (manufactured by Kuribayashi Co., Ltd.) to form a cylinder having a diameter of 40 mm, and cut into a length of 40 mm to produce a cylinder block. After the cylindrical body forming sheet is rolled into a cylindrical shape and both ends are overlapped and pressed with a heating block, if the cylindrical body forming sheets are heat-sealed without peeling off each other, the heat-sealing property is evaluated as good, Displayed with ○ mark. On the other hand, when the heating block rises and then the heating block ascends, the sheet for tubular molding adheres and peels off each other, or the heat-sealed portion peels off in the subsequent process and the soil of the contents spills out. Was evaluated as poor in heat sealability, and indicated by a mark x. When cutting the continuous cylindrical body after filling with the soil, the saw blade was caught by the constituent fibers of the sheet for forming a cylindrical body and the sheet could be cut without tearing, and the cutability was evaluated as good. On the other hand, when the cylindrical body forming sheet was not completely cut or was torn or cut off due to the transverse reciprocating movement of the saw blade, the cutability was evaluated as poor and indicated by a cross.

Seedling raising test method The cylindrical block of 40 mm in length cut above is placed in a pocket formed in a plastic tray with its bottom surface slightly raised from the bottom of the pocket. Sowed. The pockets formed in the plastic tray were formed in 6 rows and 10 columns, and the cylinder blocks were arranged in a state aligned with the plastic tray, germinated and grown for 70 days. During the seedling raising period, watering was performed periodically from the upper surface, and a plastic tray was immersed in a pool having a depth of 30 mm to irrigate by absorbing water from the bottom surface.

After 70 days of raising the seedlings, it is difficult to tear the sheet for forming the cylinder. After raising the seedlings for 70 days, the user picks up the side of the cylindrical block from the plastic tray and observes the ease of tearing of the sheet for forming the cylinder at that time. Those that did not break due to finger pressure or the friction between the cylinder and the side surface of the pocket of the plastic tray when picking up were marked with a circle, and those that broke or cracked were marked with a cross.

Biodegradation rate of cylinder-forming sheet after 70-day seedling raising The ratio of the area of the collected molding sheet to the area of the molding sheet at the start of seedling-raising after removing the cylinder-forming sheet from the cylinder block Was measured, and the biodegradation rate was determined from the following equation. Biodegradation rate (%) = (area of sheet for forming cylinder at start of seedling-area of collected sheet for forming cylinder) ÷ area of sheet for forming cylinder at start of seedling × 100

Physical Property Test of Cylindrical Forming Sheet Wet tensile strength: A test piece having a width of 15 mm and a length of 150 mm was prepared and measured according to JIS P8135. In addition,
After completion of the seedling raising period, the wet tensile strength of the cylinder forming sheet remaining in the cylinder block is determined by immersing the lower half of the cylinder block in a water tank having a depth of 20 mm for 15 minutes, pulling it up and leaving it to stand for 30 minutes. The sheet for body forming was peeled off, a test piece having a width of 15 mm and a length of 40 mm was sampled in the circumferential direction, and measured in the lateral direction of the cylindrical body forming sheet. The wet tensile strength in the vertical direction of the cylindrical body forming sheet is such that the sheet near the bottom of the cylindrical block has collapsed and a test piece having a length of 40 mm cannot be collected in the vertical direction. It was calculated from the wet tensile strength.

The longitudinal wet tensile strength (kN / m) of the tube-forming sheet after the seedling raising period is completed = the lateral wet tensile strength (kN / m) of the tube-forming sheet after the seedling raising period is completed. The longitudinal wet tensile strength (k) of the cylinder forming sheet before the end of the period
N / m) ÷ Wet tensile strength in the transverse direction (kN / m) of the cylinder-forming sheet before the end of the seedling raising period

Air permeability: It was measured using an air permeability meter (product name PPM100) manufactured by Filtrona. Basis weight: Measured according to JIS P8124. Thickness and density: Measured according to JIS P8118. Dry tensile strength: measured according to JIS P8113. Flexural rigidity: Lorentzen flexural rigidity tester (B
Using an Ending Stiffness Tester, a 38 mm × 60 mm test piece was measured at a bending angle of 20 °.

Examples of the present invention and comparative examples will be described below, but the present invention is not limited to these examples.

Example 1 Polybutylene succinate
Biodegradable thermoplastic synthetic fiber having adipate as a sheath component and polybutylene succinate as a core component (NBF-KK manufactured by Daiwabo Polytech Co., Ltd., fineness 4d, fiber length 5)
mm) 50% by mass of softwood bleached to 650 ml CSF and 42% by mass of mercerized pulp, and polyvinyl alcohol short fiber dissolved in hot water at 70 ° C. (VPB107-2 manufactured by Kuraray Co., Ltd., fineness 1d, fiber length 5 mm) A papermaking material consisting of 8% by mass was prepared. Fiber component 1 of this raw material
0.6% by mass of a polyamide polyamine epichlorohydrin resin (Nippon PMC)
WS535), and mixed paper having a basis weight of 28.6 g / m ² was produced using an inclined short-mesh paper machine. This mixed paper had an air permeability of 61400 cu and a longitudinal dry tensile strength of 0.3.
It was 2 kN / m and the wet tensile strength in the longitudinal direction was 0.20 kN / m, and had favorable physical properties as a base paper for coating and impregnation.

Cellulose acetate (acetate flakes L-30, manufactured by Daicel Chemical Industries, Ltd.) having an acetylation degree of 55% and an average degree of polymerization of 150 was mixed with an acetone: ethanol mixed solution (9:
(1 part by mass) to prepare a 2% by mass solution, and the mixed paper was impregnated and coated with a roll coater. The coated paper had a solid content of cellulose acetate of 4.2 g / m ² and an air permeability of 34400.
cu, longitudinal dry tensile strength 0.49 kN / m, longitudinal wet tensile strength 0.26 kN / m, transverse wet tensile strength 0.
The sheet had 17 kN / m and a longitudinal bending stiffness of 31 mN, and had sufficient physical properties as a tubular seedling-growing block forming sheet.

With respect to the obtained sheet for forming a cylindrical body, heat sealing property and cutting property at the time of manufacturing the cylindrical body, wet tensile strength after 70 days of seedling raising, difficulty in breaking when transferred after 70 days of seedling raising, 70 days of seedling raising The subsequent biodegradation rate was measured and is shown in Table 1. The sheet for forming a cylindrical body has good heat sealing properties and cutability during the production of the cylindrical body,
Even after 70 days of raising the seedlings, the seedlings existed in a circumferential shape around the cylindrical block to prevent collapse of the cultivation. For this reason, even if the cylinder block is picked up to be transplanted, the cylinder forming sheet is not broken and the cylinder block is not collapsed, and the cylinder block can be easily transferred. At this time, the tubular molding sheet peeled off from the tubular block had a wet tensile strength in the longitudinal direction of 0.11 kN / m, a wet tensile strength in the transverse direction of 0.07 kN / m, and a biodegradability. Was 28%.

The root of Catharanthus roseus penetrated the sheet for forming the cylinder from the lower half of the cylinder block and grew well, and the root grew only in the bottom direction of the cylinder block and became spiral at the bottom. However, there was no nemaki phenomenon in which fixation after transplantation was reduced. On the other hand, when the cylinder block is buried in the soil for 70 days without seeding, the sheet for forming the cylinder becomes fragmented and cannot be collected as a sheet, and the biodegradation rate is 5%.
8%. This suggests that the cylinder-forming sheet of the cylinder block transplanted into the soil after 70 days of raising the seedlings is largely biodegradable within several months.

Example 2 Polybutylene succinate
Biodegradable thermoplastic synthetic fiber having adipate as a sheath component and polybutylene succinate as a core component (NBF-KK manufactured by Daiwabo Polytech Co., Ltd., degree 4d, fiber length 5 m)
m) and poly d, l-lactic acid as a sheath component,
20% by mass of biodegradable thermoplastic synthetic fiber having a core component of poly l-lactic acid (Lactron manufactured by Kanebo Synthetic Co., Ltd., fineness: 2d, fiber length: 5mm) and 21% by mass of softwood bleached mercerized pulp beaten into 720ml CSF; 650ml CS
Manila hemp bleached pulp beaten into F. 21% by mass, and 70%
A papermaking raw material comprising 8% by mass of polyvinyl alcohol short fiber (VPB107-2 manufactured by Kuraray Co., Ltd., fineness: 1d, fiber length: 5 mm) dissolved in hot water at ℃ was prepared. 0.3% in terms of solid content with respect to 100% by mass of the fiber component
% By mass of a polyamide polyamine epichlorohydrin resin (WS535, manufactured by Japan PMC Co., Ltd.), and the mixture was formed on an inclined short-mesh paper machine. 2% by mass
A melamine formaldehyde resin aqueous solution (Sumitomo Chemical Industries, Ltd., Sumiretsuresin 8% AC) was applied to produce a mixed paper having a basis weight of 26.4 g / m ² . This mixed paper had an air permeability of 54900 cu, a longitudinal dry tensile strength of 0.73 kN / m, and a longitudinal wet tensile strength of 0.60 kN / m.
m, and had preferable physical properties as a base paper for coating and impregnation.

Cellulose acetate (acetate flakes L-30, manufactured by Daicel Chemical Industries, Ltd.) having an acetylation degree of 55% and an average polymerization degree of 150 was mixed with an acetone: ethanol mixed solution (9:
(1 part by mass) to prepare a 2% by mass solution, which was coated on both sides of the mixed paper with a roll coater. The coated paper had a solid content of cellulose acetate of 1.9 g / m ² and an air permeability of 3452.
0cu, longitudinal dry tensile strength 0.88kN / m, longitudinal wet tensile strength 0.65kN / m, transverse wet tensile strength 0.46kN / m, longitudinal bending stiffness 32mN, tubular seedling The sheet had sufficient physical properties as a sheet for block molding.

With respect to the obtained cylinder forming sheet, heat sealing properties and cutting properties at the time of production of the cylinder, wet tensile strength after 70 days of seedling raising, difficulty in breaking when transferred after 70 days of seedling raising, 70 days of seedling raising The subsequent biodegradation rate was measured and is shown in Table 1. The sheet for forming a cylindrical body has good heat sealing properties and cutability during the production of the cylindrical body,
Even after 70 days of raising the seedlings, the seedlings existed in a circumferential shape around the cylindrical block to prevent collapse of the cultivation. For this reason, even if the cylinder block is picked up to be transplanted, the cylinder forming sheet is not broken and the cylinder block is not collapsed, and the cylinder block can be easily transferred. At this time, the tubular molding sheet peeled off from the tubular block has a wet tensile strength in the longitudinal direction of 0.28 kN / m and a wet tensile strength in the transverse direction of 0.20 kN / m. Was 16%.

As compared with the cylindrical body forming sheet of Example 1,
Although the wet tensile strength after 70 days is high and the biodegradation rate is low, this is due to the fact that a polylactic acid-based sheath-core composite fiber having a lower biodegradation rate than the polybutylene succinate-based sheath-core composite fiber is blended. This is considered to be due to the overall effects such as the blending of manila hemp pulp for increasing the drying strength and the application of an aqueous melamine formaldehyde resin solution for increasing the wet strength. In this way, the biodegradability of the sheet for cylindrical molding can be adjusted by the combination of the raw materials and chemicals,
Those that can be sufficiently used for raising garden trees such as gold crest, which requires a seedling raising period of 180 days or more, can be obtained.

The roots of Catharanthus roseus penetrated the sheet for forming the cylinder from the lower half of the cylinder block and grew well, and the root grew only in the bottom direction of the cylinder block and became spiral at the bottom. However, there was no nemaki phenomenon in which fixation after transplantation was reduced. On the other hand, when the tubular block is buried in the soil for 70 days without seeding, the tubular forming sheet becomes fragmented and cannot be collected as a sheet, and the biodegradation rate is 3%.
1%. This suggests that the tube forming sheet of the tube block transplanted into the soil after 70 days of seedling raising has a higher biodegradation rate than during the seedling raising period, and ultimately largely biodegrades.

Comparative Example 1 Polybutylene succinate
Biodegradable thermoplastic synthetic fiber having adipate as a sheath component and polybutylene succinate as a core component (NBF-KK manufactured by Daiwabo Polytech Co., Ltd., fineness 4d, fiber length 5)
mm) and 20% by mass of softwood bleached pulp beaten to 560 ml CSF, rayon staple fiber (manufactured by Daiwabo Rayon Co., Ltd., corona SB, fineness 3d, fiber length 5m)
m) Polyvinyl alcohol short fiber (VPB107-2 manufactured by Kuraray Co., Ltd.) dissolved in 25% by mass and hot water at 70 ° C.
A papermaking raw material having a fineness of 1 d and a fiber length of 5 mm) of 5% by mass was prepared. A polyamide polyamine epichlorohydrin resin (WS535, manufactured by Nippon PMC Co., Ltd.) having a solid content of 0.6% by mass based on 100% by mass of the fiber component of this raw material.
Was added to produce a mixed paper having a basis weight of 28.5 g / m ^{2 using} an inclined short-mesh paper machine. This mixed paper has an air permeability of 96,000 c.
u, the dry tensile strength in the longitudinal direction was 0.15 kN / m, and the wet tensile strength in the longitudinal direction was 0.11 kN / m, and had favorable physical properties as a base paper for coating and impregnation.

Cellulose acetate (acetate flakes L-30, manufactured by Daicel Chemical Industries, Ltd.) having an acetylation degree of 55% and an average polymerization degree of 150 was mixed with an acetone: ethanol mixed solution (9:
(1 part by mass) to prepare a 5% by mass solution, and the mixed paper was impregnated and coated with a roll coater. The coated paper had a solid content of cellulose acetate of 11.7 g / m ² and an air permeability of 2290.
cu, longitudinal dry tensile strength 0.85 kN / m, longitudinal wet tensile strength 0.49 kN / m, transverse wet tensile strength 0.
It was 40 kN / m, the longitudinal bending stiffness was 36 mN, and the solid content of the impregnated and coated cellulose acetate was large.

With respect to the obtained cylinder forming sheet, heat sealing property and cutting property at the time of manufacturing the cylinder, difficulty in breaking when transferred after 70 days of seedling raising, biodegradation rate after 70 days seedling raising, and 70 days after seedling raising The root growth was measured and is shown in Table 1. The tubular molding sheet has a portion that cannot be adhered in a tubular shape due to insufficient heat sealing property at the time of producing the tubular body. This is because the biodegradable thermoplastic fiber is completely formed by excessively coated cellulose acetate. It turned out that it was because it was covered. The cutability of the portion bonded in a cylindrical shape was good. After the seedling was raised for 70 days, the sheet for forming a cylindrical body was present around the periphery of the cylindrical block in a strong circumferential shape to prevent collapse of the cultivated soil. For this reason, even if the cylinder block is picked up to be transplanted, the cylinder forming sheet is not broken and the cylinder block is not collapsed, and the cylinder block can be easily transferred. At this time, the biodegradation rate of the cylindrical body forming sheet peeled off from the cylindrical block was 3%.

However, roots of Catharanthus roseus could not penetrate the sheet for forming a cylindrical body, and the roots grew only in the direction of the bottom surface of the cylindrical block and a root-wounding phenomenon occurred in a spiral shape at the bottom. The commercial value as a flower seedling became extremely low, and the field transplantation test was not performed.

As described above, when the amount of the biodegradable thermoplastic resin to be impregnated or coated exceeds 10 g / m 2, the air permeability of the coated tube forming sheet becomes 10,000 or less, and It can be understood that not only the root value of the plant grown in the above step, but also the commercial value as a flower seedling is lost, and the heat sealing property at the time of forming the cylindrical body is also impaired, thereby lowering the productivity.

Comparative Example 2 Polybutylene succinate
Biodegradable thermoplastic synthetic fiber having adipate as a sheath component and polybutylene succinate as a core component (NBF-KK manufactured by Daiwabo Polytech Co., Ltd., fineness 4d, fiber length 5)
mm) and 20% by mass of softwood bleached pulp beaten to 560 ml CSF, rayon staple fiber (manufactured by Daiwabo Rayon Co., Ltd., corona SB, fineness 3d, fiber length 5m)
m) Polyvinyl alcohol short fiber (VPB107-2 manufactured by Kuraray Co., Ltd.) dissolved in 25% by mass and hot water at 70 ° C.
A papermaking raw material having a fineness of 1 d and a fiber length of 5 mm) of 5% by mass was prepared. A polyamide polyamine epichlorohydrin resin (manufactured by Nippon PMC Co., Ltd., WS53) having a solid content of 0.08% by mass relative to 100% by mass of the fiber component of this raw material.
5), and the weight is 26.4 g / m2 on an inclined short-mesh paper machine.
A mixed paper of No. ² was produced. This mixed paper has an air permeability of 9600.
0 cu, the longitudinal dry tensile strength was 0.15 kN / m, and the longitudinal wet tensile strength was 0.09 kN / m.

An anionic starch fatty acid ester emulsion (Randy CP-20AS, manufactured by Nippon Cornstarch Co., Ltd.) was applied to this mixed paper at a solid content of 3 g / m ² using a size press coater. Coated paper has air permeability of 87000c
u, longitudinal dry tensile strength 0.35 kN / m, longitudinal wet tensile strength 0.10 kN / m, longitudinal bending stiffness 31 mN
Thus, a sheet for forming a cylindrical body having extremely low wet strength was obtained.

The obtained sheet for forming a cylindrical body was measured for heat sealability and cutting property at the time of manufacturing the cylindrical body, difficulty in breaking when transferred after raising the seedling for 70 days, and biodegradation rate after raising the seedling for 70 days. 1 is shown. The sheet for forming a cylindrical body had good heat-sealing properties and cutting properties at the time of manufacturing the cylindrical body, but the portion wound around the bottom of the cylindrical block after 70 days of seedling growth was decomposed and disappeared, and the soil collapsed. It was observed. Furthermore, when the user lifts up the tubular block to transplant it, the tubular molding sheet is broken and the tubular block collapses, making it impossible to relocate the tubular block. Since the sheet for forming a cylindrical body had extremely low wet strength and could not be peeled off from the cylindrical block in a sheet shape, a test piece for measuring the wet strength could not be collected. The biodegradation rate of the sheet for forming a cylindrical body was estimated to be 60% from the total area of the pieces peeled off from the cylindrical block.

As described above, when the longitudinal or lateral wet tensile strength of the tube-forming sheet is less than 0.14 kN / m, the wet tensile strength of the tube-forming sheet is increased after 70 days of seedling raising. The sheet for forming a cylindrical body is easily broken when picking up to transfer the cylindrical block, and the cultivation of the cylindrical block collapses, making it impossible to handle.

Comparative Example 3 Polybutylene succinate
Biodegradable thermoplastic synthetic fiber having adipate as a sheath component and polybutylene succinate as a core component (NBF-KK manufactured by Daiwabo Polytech Co., Ltd., fineness 4d, fiber length 5)
mm) 50% by mass of softwood bleached to 700 ml CSF and 42% by mass of mercerized pulp, and polyvinyl alcohol short fiber dissolved in hot water at 70 ° C. (VPB107-2 manufactured by Kuraray Co., Ltd., fineness 1d, fiber length 5 mm) A papermaking material consisting of 8% by mass was prepared. Fiber component 1 of this raw material
0.3% by mass of a polyamide polyamine epichlorohydrin resin (Nippon PMC)
(WS535) was added, and a mixed paper having a basis weight of 31.0 g / m ² was produced using an inclined short-mesh paper machine. This mixed paper had an air permeability of 88100 cu and a dry tensile strength of 0.1 in the machine direction.
It was 6 kN / m, the wet tensile strength in the longitudinal direction was 0.13 kN / m, the wet tensile strength in the transverse direction was 0.09 kN / m, and the flexural rigidity in the longitudinal direction was 22 mN. This mixed paper was used as it was as a sheet for forming a cylindrical body without being impregnated with a biodegradable thermoplastic resin.

The heat-sealing property and the cutting property of this sheet for forming a cylindrical body at the time of manufacturing the cylindrical body were measured, and the results are shown in Table 1. The sheet for forming a cylindrical body has good heat-sealing properties at the time of manufacturing the cylindrical body, but a phenomenon in which saw teeth peel off constituent fibers of the sheet at the time of cutting occurs. However, it was difficult to stably manufacture the cylindrical block because the paper was torn and the paper was cut. From this, when the bending stiffness in the longitudinal direction is less than 30 mN, when the saw blade is pressed to cut the cylinder, the rigidity of the cylinder is insufficient, and the cylinder cannot resist the sudden reciprocating movement of the saw blade, and the cylinder is not moved. It can be seen that the fibers move together with the sawtooth, causing fluffing of the constituent fibers and tearing of the sheet.

[0068]

[Table 1]

Example 3 Polybutylene succinate
Biodegradable thermoplastic synthetic fiber having adipate as a sheath component and polybutylene succinate as a core component (NBF-KK manufactured by Daiwabo Polytech Co., Ltd., fineness 4d, fiber length 5)
mm) and 35% by mass of biodegradable thermoplastic synthetic fiber composed of poly 1-lactic acid (Lactron, manufactured by Kanebo Gosen Co., Ltd., fineness: 2d, fiber length: 5 mm) and 600 ml CSF
Bleached softwood pulp 28% by mass, rayon staple fiber (Daiwabo Rayon Co., Ltd., Corona SB, fineness 3
d, fiber length 5 mm) 22% by mass, and polyvinyl alcohol short fiber (Kuraray Co., Ltd., V) dissolved in hot water at 70 ° C.
A papermaking raw material comprising 8% by mass of PB107-2, fineness 1d, fiber length 3 mm) was prepared. Fiber component 100 of this raw material
0.6% by mass of a polyamide polyamine epichlorohydrin resin (Nippon PMC Co., Ltd.)
, WS535) and a grammage of 25 on a slanted short screen paper machine.
g / m ² of mixed paper was produced. This mixed paper has an air permeability of 5
1600cu, longitudinal dry tensile strength 0.69kN / m,
The wet tensile strength in the machine direction was 0.18 kN / m, and had favorable physical properties as a base paper for coating and impregnation.

Degree of saponification 21.3 mol%, average degree of polymerization 15
20 polyvinyl alcohols (UM, manufactured by Unitika Ltd.)
R-150L) was dissolved in an isopropyl alcohol: water mixture (7: 3 parts by mass) to prepare a 4% by mass solution, and the mixed paper was impregnated and coated with a roll coater. The coated paper had a solid content of polyvinyl alcohol of 5.1 g / m ² , an air permeability of 46900 cu, and a longitudinal dry tensile strength of 1.05 kN /
m, longitudinal wet tensile strength 0.24 kN / m, transverse wet tensile strength 0.21 kN / m, longitudinal bending stiffness 92 mN
And had sufficient physical properties as a tubular seedling raising block forming sheet.

With respect to the obtained cylinder forming sheet, heat sealability and cutting property at the time of production of the cylinder, wet tensile strength after 70 days of seedling raising, difficulty in breaking when transferred after 70 days of seedling raising, 70 days of seedling raising The subsequent biodegradation rate was measured and is shown in Table 2. The sheet for forming a cylindrical body had good heat sealing properties and cutting properties at the time of manufacturing the cylindrical body, and was present around the cylindrical block even after 70 days of raising the seedlings to prevent collapse of the soil. For this reason, even if the cylinder block is picked up to be transplanted, the cylinder forming sheet is not broken and the cylinder block is not collapsed, and the cylinder block can be easily transferred. At this time, the tubular molding sheet peeled off from the tubular block has a wet tensile strength in the longitudinal direction of 0.03 kN / m and a wet tensile strength in the transverse direction of 0.02 kN / m. Was 15%.

The root of Catharanthus roseus penetrates the sheet for forming the cylinder from the lower half of the cylinder block and grows well. The root grows only in the direction of the bottom surface of the cylinder block and spirals at the bottom. However, there was no nemaki phenomenon in which fixation after transplantation was reduced. On the other hand, when the cylindrical block was directly buried in the soil for 70 days without seeding, the sheet for forming the cylindrical body was easily broken, a part of the sheet could not be recovered, and the biodegradation rate was 32%. This suggests that the tube forming sheet of the tube block transplanted into the soil after 70 days of seedling raising has a higher biodegradation rate than during the seedling raising period, and ultimately largely biodegrades.

Example 4 Polyvinyl alcohol having a saponification degree of 9.4 mol% and an average polymerization degree of 1500 (unitika)
UMR-150L) was dissolved in an isopropyl alcohol: water mixture (7: 3 parts by mass) to prepare a 2% by mass solution, and the base paper for coating and impregnation of Example 3 was impregnated and coated with a roll coater. . The coated paper has a solid content of polyvinyl alcohol of 3.1 g / m ² , a permeability of 50800 cu, a longitudinal dry tensile strength of 0.92 kN / m, a longitudinal wet tensile strength of 0.20 kN / m and a lateral wetness. Tensile strength 0.17kN
/ M, and the bending stiffness in the longitudinal direction was 82 mN, and had sufficient physical properties as a tubular nursery block forming sheet.

With respect to the obtained sheet for forming a cylindrical body, heat sealing property and cutting property at the time of manufacturing the cylindrical body, wet tensile strength after 70 days of seedling raising, difficulty in breaking when transferred after 70 days of seedling raising, 70 days of seedling raising The subsequent biodegradation rate was measured and is shown in Table 2. The sheet for forming a cylindrical body had good heat sealing properties and cutting properties at the time of manufacturing the cylindrical body, and was present around the cylindrical block even after 70 days of raising the seedlings to prevent collapse of the soil. For this reason, even if the cylinder block is picked up to be transplanted, the cylinder forming sheet is not broken and the cylinder block is not collapsed, and the cylinder block can be easily transferred. At this time, the cylindrical body forming sheet peeled off from the cylindrical block has a wet tensile strength of 0.02 kN / m in both the vertical and horizontal directions and a biodegradation rate of 1
3%.

The roots of Catharanthus roseus penetrated the sheet for forming the cylinder from the lower half of the cylinder block and grew well, and the roots grew only in the direction of the bottom surface of the cylinder block and spiraled at the bottom. However, there was no nemaki phenomenon in which fixation after transplantation was reduced. On the other hand, when the cylindrical block was buried in the cultivated soil for 70 days without seeding, the sheet for cylindrical forming was broken into pieces, and a part of the sheet could not be recovered, and the biodegradation rate was 38%. This suggests that the tube forming sheet of the tube block transplanted into the soil after 70 days of seedling raising has a higher biodegradation rate than during the seedling raising period, and ultimately largely biodegrades.

Example 5 Polyvinyl alcohol (UMR-150L, manufactured by Unitika Ltd.) having a saponification degree of 21.3 mol% and an average degree of polymerization of 1520 was mixed with isopropyl alcohol: water (7: 3 parts by mass). And a 2% by mass solution was prepared, and impregnated with a roll coater on the coating and impregnating base paper of Example 3. The coated paper had a solid content of polyvinyl alcohol of 2.0 g / m ² , 52400c air permeability
u, longitudinal dry tensile strength 0.90 kN / m, longitudinal wet tensile strength 0.14 kN / m, transverse wet tensile strength
17 kN / m, the bending rigidity in the longitudinal direction was 54 mN, and it had sufficient physical properties as a tubular seedling-growing block forming sheet.

With respect to the obtained sheet for forming a cylindrical body, heat sealing property and cutting property at the time of manufacturing the cylindrical body, wet tensile strength after 70 days of seedling raising, difficulty in breaking when transferred after 70 days of seedling raising, 70 days of seedling raising The subsequent biodegradation rate was measured and is shown in Table 2. The sheet for forming a cylindrical body had good heat sealing properties and cutting properties at the time of manufacturing the cylindrical body, and was present around the cylindrical block even after 70 days of raising the seedlings to prevent collapse of the soil. For this reason, even if the cylinder block is picked up to be transplanted, the cylinder forming sheet is not broken and the cylinder block is not collapsed, and the cylinder block can be easily transferred. At this time, the tubular body forming sheet peeled off from the tubular block has a wet tensile strength of 0.01 kN / m in both the longitudinal and transverse directions and a biodegradation rate of 3
5%.

The roots of Catharanthus roseus penetrated the sheet for forming the cylinder from the lower half of the cylinder block and grew well, and the root grew only in the bottom direction of the cylinder block and became spiral at the bottom. However, there was no nemaki phenomenon in which fixation after transplantation was reduced. On the other hand, when the cylindrical block was buried in the cultivated soil for 70 days without seeding, the cylindrical molding sheet was broken into pieces and could not be recovered, and the biodegradation rate was 53%. This suggests that the tube forming sheet of the tube block transplanted into the soil after 70 days of seedling raising has a higher biodegradation rate than during the seedling raising period, and ultimately largely biodegrades.

Further, as compared with the sheet for forming a cylindrical body of the cylindrical block according to the third embodiment, the amount of adhered solids of polyvinyl alcohol was reduced to less than half. As a result, the biodegradation rate after transplanting the soil was higher than that of the third embodiment. It can be seen that the biodegradation rate can be adjusted by changing the solid content of polyvinyl alcohol.

Comparative Example 4 A 4% by mass solution was prepared by dissolving a water-soluble polyvinyl alcohol (UMR-30M, manufactured by Unitika Ltd.) having a degree of saponification of 65 mol% and an average degree of polymerization of 600 in water. The base paper for coating and impregnation in Example 3 was impregnated and coated with a roll coater. The coated paper has a solid content of polyvinyl alcohol of 5.2 g / m ² and an air permeability of 47600 c.
u, the longitudinal dry tensile strength is 0.90 kN / m, the longitudinal bending stiffness is 79 mN, but the longitudinal wet tensile strength is 0.05 kN.
N / m and the transverse wet tensile strength were as low as 0.06 kN / m, so that the wet tensile strength was insufficient for use as a tubular nursery block forming sheet.

The obtained sheet for forming a cylindrical body was heat-sealed and cut during the production of the cylindrical body, the wet tensile strength after 70 days of seedling raising, the difficulty in breaking when transferred after 70 days of seedling raising, the 70 days of seedling raising The subsequent biodegradation rate was measured and is shown in Table 2. The tubular molding sheet has good heat sealing properties and cutting properties at the time of producing the tubular body, but has extremely low wet strength after 70 days of seedling raising, and is easily broken when picked up to transplant the tubular block. Also, it could not be peeled off from the soil of the cylinder block.

As described above, when the degree of saponification of the polyvinyl alcohol to be impregnated or applied exceeds 60 mol%,
The wet tensile strength of the tube-forming sheet is less than 0.14 kN / m, and after 70 days of raising the seedlings, the wet-tensile strength of the tube-forming sheet is completely absent, and the cultivation of the cylindrical block collapses and handling becomes unacceptable. It becomes possible.

[0083]

[Table 2]

[0084]

According to the present invention, a biodegradable sheet material for forming a seedling-growing block suitable for manufacturing a seedling-growing block having a short cylindrical shape by wrapping the soil to form a continuous cylindrical body and cutting the continuous cylindrical body. In addition to breathability, water permeability, and moisture resistance, it has heat sealing properties when forming into a cylindrical body, easy cutting properties when cutting into a short cylindrical body, and retains its shape during the seedling raising period. A biodegradable sheet material that decomposes in soil.

[Brief description of the drawings]

FIG. 1 is a cutaway perspective view of a continuous tubular body in which a soil is wrapped in a biodegradable sheet material.

FIG. 2 is a perspective view of a short tubular seedling raising block.

FIG. 3 is a cross-sectional view for explaining a cylinder molding machine.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) D21H 13/10 D21H 13/10 13/16 13/16 19/20 19/20 B 21/20 21/20 (72) Inventor Yukiyuki Hattori 90-2 Eo, Fuji City, Shizuoka Prefecture F-term in Mishima Paper Co., Ltd.Development Research Laboratory 2B027 NB01 NC02 NC23 NC31 NC37 NC39 NC52 ND03 ND09 NE05 QA02 4L055 AA02 AA07 AF09 AF10 AF13 AF21 AF26 AF33 AF44 AF46 AF47 AG46 AG64 AG81 AG87 AH17 AH37 AJ02 BE08 BE10 EA07 EA12 FA13 FA20 GA25

Claims (5)

[Claims] 1. A mixed paper made by blending short fibers of biodegradable thermoplastic synthetic fibers, papermaking fibers and polyvinyl alcohol short fibers as a raw material for papermaking, and adding a wet strength enhancer to the biodegradable thermoplastic. Impregnated or coated with resin, air permeability 10,000
A biodegradable sheet material for forming a nursery block, wherein the sheet material has a wet tensile strength of at least 00 cu, a wet tensile strength of at least 0.14 kN / M, and a bending stiffness of at least 30 mN. 2. The blending ratio of short fibers of biodegradable thermoplastic synthetic fibers, fibers for papermaking and short fibers of polyvinyl alcohol is 30 to 95:60 to 4: 1 to 10 by mass. Item 4. A biodegradable sheet material for molding a seedling raising block according to Item 1. 3. The method according to claim 1, wherein the amount of the wet-strength enhancer is 1%.
The biodegradable sheet material for forming a seedling raising block according to claim 1, wherein the ratio of the solid content is 0.1 to 5% by mass with respect to 00% by mass. 4. The biodegradable sheet material for forming a nursery block according to claim 1, wherein the amount of the biodegradable thermoplastic resin to be impregnated or applied is 1 to 10 g / m ² . 5. The seedling raising block according to claim 1, wherein the biodegradable thermoplastic resin to be impregnated or coated is polyvinyl alcohol having a saponification degree of 8 to 60 mol%. Biodegradable sheet material for molding.