Seedling raising pot with stability over time and method for promoting its decomposition

Abstract

[Problem] To provide a seedling-growing pot body that exhibits long-term stability, that suppresses decomposition during seedling growth, that maintains sufficient strength during planting, and that, through enzymatic treatment immediately before and / or immediately after planting, rapidly decomposes after being planted in a field. [Solution] A base paper for this seedling-growing pot body and a seedling-growing pot body obtained by molding the base paper are characterized by being formed by providing, on at least one surface of a paper substrate, a biodegradable resin layer containing at least 15% by mass of polylactic acid relative to 100% by mass of a biodegradable resin composition.

Description

[Technical Field]

[0001] The present invention relates to seedling raising pots used in the fields of agriculture or horticulture, and relates to base paper for seedling raising pots that maintain the shape of the pots during the seedling raising period, can be planted in the ground as is after the seedlings have been raised, is rapidly biodegradable after planting, and has excellent stability over time when stored for a long period of time; seedling raising pots made by molding and processing the base paper; and a method for promoting the decomposition of the seedling raising pots. [Background technology]

[0002] A seedling transplantation cultivation method has been widely used in the past, in which plants are cultivated in paper pots processed into a square or hexagonal prism shape. In this cultivation method, the square or hexagonal prism shape made of paper is filled with culture soil, seeds are sown, the seedlings are raised under controlled irrigation, and the raised seedlings are planted in the pots, i.e., the potted seedlings, in a field for cultivation.

[0003] In the continuous aggregate pot for transplanting seedlings shown in Patent Document 1, individual square or hexagonal cylindrical pots are connected by connecting pieces to form a continuous body. Patent Document 2 also shows that when using a simple transplanter to continuously pull out the potted seedlings from one end and plant them one by one, it is necessary to maintain the continuous state of the continuous potted seedlings without separating them into individual pieces.

[0004] Patent Documents 3 and 4 disclose that seedling pots made using a laminated sheet with a thermoplastic biodegradable resin layer on a paper base material have the property of quickly decomposing after planting in a field.

[0005] On the other hand, Patent Documents 5 and 6 disclose a technique for controlling the progress of decomposition at any timing by directly administering a microbial enzyme to an agricultural mulch film laid in a field. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4543393 [Patent Document 2] Patent No. 6126486 [Patent Document 3] Patent No. 4763123 [Patent Document 4] Japanese Patent Publication No. 2004-121054 [Patent Document 5] Patent No. 6338183 [Patent Document 6] Patent Gazette No. 5849297 [Patent Document 7] Special Public Notice No. 38-025715 [Patent Document 8] Patent No. 6413117

Non-licensed literature

[0007]

Non-patent document 1

Non-patent document 2

Non-patent document 3

[0008] As proposed or suggested in Patent Documents 1 and 2, the paper for the continuous pots is required to have physical strength, i.e., tensile strength, that can withstand the tension that occurs mainly when the pots are pulled out toward the field during the entire process leading up to planting. However, conventional base paper for seedling raising pots tends to have a slow decomposition rate in the field as it provides sufficient strength during the seedling raising period and at planting. Therefore, if decomposition is incomplete and does not occur in time for the next crop, agricultural work and crop harvesting may be hindered. Therefore, seedling raising pots are required to have the contradictory properties of suppressing the progress of decomposition during seedling raising to maintain sufficient strength at planting, while also decomposing quickly after planting in the field. Patent Documents 3 and 4 disclose that by applying a thermoplastic biodegradable resin layer to a seedling pot, the seedling pot will decompose after planting in a field; however, no technology has yet been established to arbitrarily control decomposition during seedling raising and after planting. Furthermore, Patent Documents 5 and 6 disclose a technology for controlling the progress of biodegradation of agricultural mulch film at any time by directly administering enzymes derived from microorganisms. However, agricultural mulch film and seedling pots differ in the properties of the material, including the intended use of the material, the situations and conditions in which they are used, and the physical strength and chemical properties required accordingly, and therefore cannot be simply interchanged. Furthermore, in addition to having sufficient strength during the seedling raising period and at the time of planting, seedling pot base paper is also required to be stable over time, since seedling pots tend to deteriorate over time after production. [Means for solving the problem]

[0009] The present invention has been made to solve the above-mentioned problems, and biodegradable resins may be used alone or in combination of two or more. Specifically, the present invention provides a base paper for seedling pots, which is finished by laminating, on at least one side of paper, a biodegradable resin composition containing the following biodegradable resins in the following proportions. Furthermore, the present invention provides seedling pots made from the base paper for seedling pots, which are treated with a microbial enzyme immediately before and / or immediately after planting, thereby maintaining a certain level of strength at the time of planting while controlling the progress of decomposition after planting, thereby providing seedling pots with excellent stability over time.

[0010] That is, the present invention relates to the following group of inventions. 1. A base paper for seedling pots, characterized in that it is formed by laminating a biodegradable resin composition containing 15% by mass or more of a polylactic acid-based resin as the resin (A) on a paper base material. 2. The biodegradable resin composition contains an aliphatic polyester resin other than a polylactic acid resin as resin (B), 2. The base paper for seedling pots according to item 1 above, wherein the mass ratio of the resin (A) to the resin (B) is 15:85 to 40:60. 3. The biodegradable resin composition contains an aliphatic polyester resin other than a polylactic acid resin as resin (B) and an aromatic polyester resin as resin (C), the resin (B) is contained in an amount of 30 to 84.9% by mass relative to the total mass of the biodegradable resin composition, 2. The base paper for seedling pots according to item 1 above, wherein the resin (C) is contained in an amount of 0.1 to 30% by mass relative to the total mass of the resin composition components. 4. The base paper for seedling pots according to any one of items 1 to 3 above, wherein the resin (A) is polylactic acid. 5. A base paper for seedling pots according to any one of items 2 to 4 above, characterized in that resin (B) is an aliphatic polyester-based resin obtained by polycondensation of a dicarboxylic acid component consisting of an aliphatic dicarboxylic acid and a diol component consisting of an aliphatic diol. 6. A base paper for seedling pots according to any one of items 2 to 5 above, characterized in that the resin (B) is at least one selected from polybutylene succinate (PBS), polybutylene succinate adipate (PBSA) and polyhydroxybutyric acid. 7. A base paper for seedling pots according to any one of items 3 to 6, characterized in that the resin (C) is an aromatic polyester resin obtained by polycondensation of a dicarboxylic acid component consisting of an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid and a diol component consisting of an aliphatic diol. 8. The base paper for seedling pots according to any one of items 3 to 7 above, wherein the resin (C) is polybutylene adipate terephthalate (PBAT). 9. A seedling pot comprising the base paper for seedling pots according to any one of items 1 to 8 above. 10. A method for decomposing seedling pots, comprising the step of contacting the seedling pots according to item 9 above with a biodegradable resin-decomposing enzyme to biodegrade the seedling pots. 11. A method for decomposing seedling pots according to claim 10, characterized in that the biodegradable resin-degrading enzyme is produced by at least one microorganism selected from the group consisting of yeasts of the genus Pseudozyma, yeasts of the genus Cryptococcus, fungi of the genus Acremonium, fungi of the genus Alternaria, fungi of the genus Arthrinium, fungi of the genus Aureobasidium, fungi of the genus Cladosporium, fungi of the genus Epicoccum, fungi of the genus Fusarium, fungi of the genus Paraphoma, and fungi of the genus Penicillium. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a base paper for seedling pots and seedling pots having the following characteristics. That is, seedling pots made from the seedling pot base paper of the present invention have sufficient strength during the seedling raising period and at the time of planting because decomposition during seedling raising is suppressed. This allows for smooth planting in the field. Furthermore, because the seedling pots can maintain their shape during seedling raising, the seedlings are not damaged during planting, resulting in a high rate of planting survival. Furthermore, seedling pots made from the seedling pot base paper of the present invention have excellent stability over time when stored for long periods. Furthermore, seedling pots made from the seedling pot base paper of the present invention can be treated with an enzyme just before and / or immediately after planting in the field, which controls the progress of biodegradation of the pots in the soil and allows the pots to gradually disintegrate. This allows the seedling roots to grow freely and does not hinder seedling growth. Furthermore, the amount of seedling pot residue remaining due to insufficient decomposition can be reduced, preventing it from affecting the next crop. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a graph showing the tensile strength of biodegradable resin composition laminated paper (laminate thickness: 30 μm) without enzyme treatment after 2 weeks of burial for (A) a sample manufactured less than 1 year ago and (B) a sample manufactured 2 years ago. [Figure 2]Figure 2 is a graph showing the tensile strength of biodegradable resin composition laminated paper (laminate thickness: 15 μm) without enzyme treatment after 2 weeks of burial for (A) a sample manufactured less than 1 year ago and (B) a sample manufactured 2 years ago. [Figure 3] FIG. 3 is a graph showing the tensile strength of biodegradable resin composition laminated paper (laminate thickness: 30 μm) that was produced two years ago with and without enzyme treatment, after (A) two weeks of burial and (B) four weeks of burial. [Figure 4] FIG. 4 is a graph showing the tensile strength of corona-treated biodegradable resin composition laminated paper (laminate thickness: 30 μm) that was produced less than one year ago with and without enzyme treatment, two weeks (A) and four weeks (B) after burial. [Figure 5] Figure 5 is a graph showing the tensile strength of biodegradable resin composition laminated paper (laminate thickness: 30 μm) that was not corona-treated and that was produced less than one year ago, with and without enzyme treatment, two weeks (A) and four weeks (B) after burial. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Seedling pot body> The seedling pots are made by laminating a biodegradable resin composition on at least one side of a paper substrate, and molding the laminated paper into, for example, a square or hexagonal prism. The individual pots can then be connected with connecting pieces to form a continuous pot.

[0014] The main characteristics required of base paper for seedling pots are: (1) having enough paper strength when dry to withstand mechanical processing such as bending and pulling during the production of the pots; (2) being prone to deterioration over time after the pots are manufactured; (3) being resistant to biodegradation by microorganisms during seedling cultivation (rot resistance); (4) having enough paper strength when wet to withstand mechanical and artificial handling when planting the seedlings in the field after cultivation by maintaining rot resistance; and (5) having brittleness after planting that allows roots to grow quickly from the side walls of the pot regardless of the nature of the soil, and having the soil disintegration properties that allow biodegradation by the action of soil microorganisms and the like.

[0015] In particular, biodegradability (property (5)) is required after planting, which contradicts resistance to deterioration (property (2) above) and rot resistance (property (3) above) before planting. Therefore, it is a challenge to establish these contradictory properties in a single seedling pot base paper. Furthermore, the specifications of the seedling pots (for example, the differences between Patent Document 1 and Patent Document 7, as described below), the seedling raising period, the seedling management conditions (management temperature, amount of irrigation, etc.), and the paper strength of the seedling pots when wetted required at planting vary depending on the crop to be used or the type of work involved. Therefore, it is necessary to balance and adjust each of the properties (1) to (5) within an appropriate range, and thereby appropriately set the physical and chemical strength of the seedling pots according to the type of crop.

[0016] Specifically, the characteristic (4) can be expressed as an index of tensile strength (measured with an autograph tensile tester in accordance with JIS P8113:1998). When the continuous aggregate pot for raising and transplanting seedlings shown in Patent Document 1 is assumed to be planted using the simple transplanter shown in Patent Document 2, the tensile strength at the end of raising seedlings (at the time of planting) is desirably 10 N / 30 mm or more, more preferably 15 N / 30 mm or more, and particularly preferably 20 N / 30 mm or more. On the other hand, in the case of the type of seedling raising pot that separates into individual paper containers (pots) shown in Patent Document 7, it is sufficient that the cylindrical shape of the paper container is maintained, and a tensile strength of 5 N / 30 mm or more is desirable. Note that this strength can be adjusted by appropriately setting the basis weight of the paper base material and the thickness of the biodegradable resin layer.

[0017] <Paper base material> The paper substrate used in the present invention is not particularly limited in terms of the type of raw pulp or the amount of cellulose fiber contained therein, as long as it contains cellulose fiber as the main component. Examples include paper containing pulp commonly used in papermaking. More specifically, examples include unbleached, semi-bleached, or bleached kraft pulp, sulfite pulp, semi-chemical pulp, soda pulp, mechanical pulp from softwoods and hardwoods, and recycled paper. These may be used alone or in combination of two or more. Unbleached pulp is particularly preferred.

[0018] The paper used in the present invention may contain, as needed, various auxiliary agents typically used in papermaking, such as binders, fillers, paper strength agents, sizing agents, retention aids, and preservatives, as well as synthetic fibers such as polyethylene and polyester. The paper may also be sized with starch, polyvinyl alcohol, or the like, and may have a coating layer or a resin coating layer whose main component is an inorganic pigment.

[0019] The basis weight of the paper substrate is not particularly limited, but is preferably 20 to 200 g / m 2 It is preferable that the density is 30 to 100 g / m 2 More preferably, 45 to 90 g / m 2 is particularly preferred.

[0020] <Biodegradable resin> "Biodegradable resin" Biodegradable resins are resins that have the same functions as conventional petroleum-derived plastics when in use, but after use are biodegraded by microorganisms in the soil and water of nature over a certain period of time, and are ultimately hydrolyzed into water and carbon dioxide. Examples of the biodegradable resin used in the present invention include aliphatic polyester resins and aromatic polyester resins. The aliphatic polyester of the present invention refers to an aliphatic polyester that does not contain an aromatic ring, and the aliphatic polyester resin refers to an aliphatic polyester resin that does not contain an aromatic ring. Furthermore, the aromatic polyester of the present invention refers to a polyester that contains an aromatic ring, and the aromatic polyester resin refers to a polyester resin that contains an aromatic ring.

[0021] Examples of aliphatic polyester resins include polylactic acid (PLA), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polycaprolactone (PCL), polyhydroxybutyric acid (PHB), polyhydroxyvalerate (PHV), and copolymers thereof (PHVB).

[0022] The polylactic acid resin is referred to as resin (A) in the present invention. The polylactic acid resin is not particularly limited as long as it is a condensation product of lactic acid, and may be a poly-L-lactic acid resin, a poly-D-lactic acid resin, or a mixture thereof (for example, a stereocomplex polylactic acid resin obtained by mixing a poly-L-lactic acid resin and a poly-D-lactic acid resin).

[0023] Furthermore, aliphatic polyester resins other than polylactic acid resins are referred to as resin (B) of the present invention. Aliphatic polyester resins other than polylactic acid resins are aliphatic polyester resins obtained by esterification or transesterification of a dicarboxylic acid component consisting of an aliphatic dicarboxylic acid and a diol component consisting of an aliphatic diol, followed by a polycondensation reaction. For example, polybutylene succinate (PBS) is obtained by esterification or transesterification of a dicarboxylic acid component consisting of succinic acid and a diol component consisting of 1,4-butanediol, followed by a polycondensation reaction. Other components may also be included. For example, other dicarboxylic acid components and other diol components may be included. Examples of other dicarboxylic acid components include aliphatic dicarboxylic acids such as adipic acid, sebacic acid, and itaconic acid. Examples of other diol components include 2,3-butanediol, 1,3-butanediol, 1,4-pentanediol, 2,4-pentanediol, 1,6-hexanediol, neopentyl glycol, ethylene glycol, and diethylene glycol.

[0024] Examples of aromatic polyester resins that can be used as the resin (C) of the present invention include polybutylene adipate terephthalate resins, polybutylene terephthalate alkylate resins, and polybutylene succinate terephthalate resins. Polybutylene adipate terephthalate (PBAT) is particularly preferred. Polybutylene adipate terephthalate (PBAT) is produced by a polycondensation reaction between a dicarboxylic acid component consisting of adipic acid and terephthalic acid and a diol component consisting of 1,4-butanediol, but other components may also be included. For example, other diol components may also be included. Examples of other diol components include 2,3-butanediol, 1,3-butanediol, 1,4-pentanediol, 2,4-pentanediol, 1,6-hexanediol, neopentyl glycol, ethylene glycol, and diethylene glycol.

[0025] "Biodegradable resin blend ratio" The biodegradable resins may be used alone or in combination of two or more. In particular, when film formability and physical properties are taken into consideration, aliphatic polyesters or aromatic polyesters having a melting point of 50 to 180°C and a weight-average molecular weight of 50,000 or more are preferred for obtaining good molded products. Furthermore, when biodegradability, flexibility, and stability over time are required, a mixed resin consisting of two or more types of resins containing 15% by mass or more of a polylactic acid-based resin relative to the total mass of the biodegradable resin composition is preferred. By using this mixed resin in seedling-raising pots, the seedlings do not decompose during raising, maintaining a certain strength at the time of planting, and enzyme treatment immediately before and / or after planting can accelerate the progress of decomposition after planting in the field.

[0026] The content of the polylactic acid resin (resin (A)) is in the range of 15 to 40% by mass, preferably 18 to 35% by mass, and particularly preferably 20 to 30% by mass, based on the total mass of the biodegradable resin composition. A biodegradable resin composition in this range is suitable for maintaining the various properties of moldability, flexibility, stability over time, rot resistance during seedling raising, and decomposition by biodegradable resin-degrading enzymes.

[0027] The content of the above aliphatic polyester resin (other than polylactic acid resin) (resin (B)) is in the range of 60 to 85 mass%, preferably 65 to 82 mass%, particularly preferably 70 to 80 mass%, relative to the total mass of the biodegradable resin composition.

[0028] In addition to the above-mentioned aliphatic polyester resin not containing an aromatic ring, an aromatic polyester resin (resin (C)) may optionally be contained to adjust the rate of soil decomposition in the field and the enzymatic reactivity. In this case, the content of the resin (B) is 30 to 84.9 mass%, preferably 45 to 77 mass%, and particularly preferably 55 to 72 mass%, relative to the total mass of the biodegradable resin composition. The content of the resin (C) is 0.1 to 30 mass%, preferably 5 to 20 mass%, and particularly preferably 8 to 15 mass%, relative to the total mass of the biodegradable resin composition. These contents are suitable for maintaining the properties required of seedling raising pots, such as rot resistance during the seedling raising period, decomposition by biodegradable resin-degrading enzymes, as well as moldability and flexibility.

[0029] Examples of aliphatic polyester resins include "BioPBS (registered trademark) FZ71PM" manufactured by PTTMCC Biochem (aliphatic polyester resin obtained by polycondensation of 1,4-butanediol and succinic acid, melting point: approximately 115°C) and "GSPLA (registered trademark) FZ71PN" manufactured by Mitsubishi Chemical Corporation (same as above, melting point: approximately 115°C). An example of the polylactic acid resin is "Ingeo (registered trademark) 4032D" manufactured by NatureWorks. An example of an aromatic polyester resin is BASF's "Ecoflex" (aromatic polyester resin obtained by polycondensation of an aromatic polyester made from 1,4-butanediol, adipic acid, and terephthalic acid, melting point: approximately 110°C).

[0030] Furthermore, the moldability can be further improved by using an antiblocking agent in the biodegradable resin composition in an amount of 1 to 10% by mass per 100% by mass of the biodegradable resin composition. Specific examples of antiblocking agents include stable metal oxides such as silica, titanium dioxide, and alumina, stable metal salts such as calcium carbonate, calcium phosphate, and barium sulfate, and so-called organic beads in which polylactic acid resin is coated with an inactive organic resin. These antiblocking agents may be used alone or in combination of two or more.

[0031] In addition, in the present invention, in addition to PCL, PBS, PBSA, biodegradable aromatic polyester resin, and nucleating agent, known biodegradable resins, non-biodegradable resins, inorganic fillers, organic fillers, inorganic pigments, organic pigments, UV absorbers, light stabilizers, antioxidants, and lubricants may be blended within the scope of the invention.

[0032] "Lamination method (lamination)" The biodegradable seedling pots of the present invention comprise a laminate sheet made by laminating the above-mentioned biodegradable resin on at least one side of paper. The laminate sheet is made by subjecting the surface of the base paper to corona discharge treatment, flame treatment, anchor coating treatment, etc., and then extruding and laminating the biodegradable resin onto the treated surface. To increase the processing stability of the extrusion laminate, a method is also available in which a general-purpose plastic such as polyethylene is co-extruded with the biodegradable resin, and then the general-purpose plastic film is peeled off to obtain a laminate sheet of paper and biodegradable resin. The thickness of the biodegradable resin layer laminated on the paper base material is not particularly limited, but is preferably 5 to 80 μm, more preferably 15 to 50 μm, and particularly preferably 20 to 35 μm. The thickness of the resin layer can be adjusted to suit the physical strength of the seedling pot and the progress of decomposition by enzyme treatment.

[0033] <Method for decomposing biodegradable resin> "Biodegradable resin-degrading enzyme" As the biodegradable resin-degrading enzyme, any conventionally known enzyme can be used, including, for example, hydrolases such as lipase, cutinase, esterase, protease, lysophospholipase, amylase, glucoamylase, peptidase, serine hydrolase, cellulase, chitinase, xylanase, and pectinase, and oxidoreductases such as peroxidase, monooxygenase, dioxygenase, and laccase, with lipase, cutinase, esterase, protease, and amylase being preferred. Specifically, the cutinase-like enzyme PaE produced by the yeast Pseudozyma antarctica, CmCut1 produced by the Cryptococcus magnus-related strain BPD1A, CfCLE GB-1 and CfCLE Sb19-1 produced by the Cryptococcus flavus GB-1 strain and CfCLE Sb19-1 produced by the Cryptococcus flavus Sb19-1 strain, CLE produced by the Cryptococcus sp. S-2 strain, and PCLE produced by the Paraphoma genus filamentous fungus B47-9 strain can be used. These biodegradable resin-degrading enzymes each have different optimal pH and temperature ranges for maximum enzymatic activity, and these properties can be utilized to appropriately perform the desired enzymatic reaction. For example, PaE exhibits high enzymatic activity in the neutral to alkaline range, with an optimal pH of 9.5 (Non-Patent Document 1). On the other hand, PCLE exhibits high enzymatic activity near the neutral pH range, with an optimum pH of 7.2 (Non-Patent Document 2). Additionally, it is known that the optimum pH of CmCut1 is 7.5 (Non-Patent Document 3), and that of CfCLE GB-1 is 7.8 (Non-Patent Document 4).

[0034] The origin of enzymes The microorganisms that produce biodegradable resin-degrading enzymes are not particularly limited, and any strains, such as strains isolated from nature, can be used. Specifically, the microorganisms include those of the genera Pseudomonas, Pseudozyma, Cryptococcus, Acremonium, Alternaria, Arthrinium, Aureobasidium, Cladosporium, Epicoccum, Fusarium, and Paraforma. Examples of microorganisms that can be used include those of the genera Homa, Penicillium, Bacteroides, Mucor, Humicola, Thermomyces, Talaromyces, Chaetomium, Torula, Sporotrichum, Malbranchea, and Acidovorax. More specifically, the foliar yeast Pseudozyma antarctica, the Cryptococcus magnus-related strain BPD1A, Cryptococcus flavus GB-1 strain, and Cryptococcus flavus Sb19-1 strain, Pseudozyma antarctica isolated from rice grains collected in Ibaraki Prefecture and deposited at the National Institute of Technology and Evaluation Patent Organism Depositary with accession number FERM BP-22155 (deposit date July 22, 2011), the filamentous fungus deposited at the National Institute of Technology and Evaluation Patent Microorganism Depositary with accession number NITE P-573, and Pseudozyma antarctica JCM10317 strain provided as a standard strain at the RIKEN BioResource Center can be used.In particular, it is preferable to use at least one selected from the group consisting of the cutinase-like enzyme PaE produced by the yeast Pseudozyma antarctica, CmCut1 produced by the Cryptococcus magnus-related strain BPD1A, CfCLE GB-1 produced by the Cryptococcus flavus GB-1 strain and CfCLE Sb19-1 produced by the Cryptococcus flavus Sb19-1 strain, CLE produced by the yeast Cryptococcus under accession number FERM P-15155, and PCLE produced by the filamentous fungus Paraphoma under accession number NITE P-573, or a mixture of culture media thereof.

[0035] Furthermore, nucleic acids encoding biodegradable resin-degrading enzymes can be recombined into bacteria, eukaryotic microorganisms, cultured cells, etc. to artificially express biodegradable resin-degrading enzymes. A specific example is the cutinase-like enzyme PaE produced by the yeast Pseudozyma antarctica, as follows: The gene PaCLE1 encoding PaE is registered under GenBank Accession No. DM067526, and a method is known in which PaCLE1 is incorporated into Pseudozyma antarctica or a species closely related to Pseudozyma antarctica by the method described in paragraphs

[0034] to

[0038] of Patent Document 8, and PaE is obtained from the transformant.

[0036] "Polymer water absorbent" In the method for decomposing biodegradable seedling pots of the present invention, in addition to the biodegradable resin-degrading enzyme, a polymeric water-absorbing agent may be applied to the pot. Examples of polymeric water-absorbing agents include, but are not limited to, highly water-absorbent polymers that have sufficient water-retaining capacity and adhere to the surface of biodegradable seedling pots while retaining water, starch derivatives, carboxyalkyl cellulose, hydroxyalkyl cellulose, polysaccharide derivatives, crosslinked polyamino acids, and water-absorbing materials made from fruit and vegetable waste. Among these, carboxyalkyl cellulose is preferred, and carboxymethyl cellulose is particularly preferred. By applying these polymeric water-absorbing agents to biodegradable seedling pots, the polymeric water-absorbing agent containing water and the biodegradable resin-degrading enzyme is maintained on the surface of the biodegradable resin material for a long period of time, facilitating the decomposition of the biodegradable seedling pots.

[0037] "Calcium ingredients mixed with enzymes" The enzymatic reaction can be further accelerated by adding a calcium component to a biodegradable resin-degrading enzyme (Patent Document 5). When a biodegradable resin is decomposed by immersing it in an enzyme solution containing a biodegradable resin-degrading enzyme, the pH of the enzyme solution gradually decreases. Therefore, by maintaining the pH of the target material for enzyme treatment between neutral and slightly alkaline, taking into consideration the optimal pH of the biodegradable resin-degrading enzyme, decomposition by the biodegradable resin-degrading enzyme can be efficiently carried out. Materials that are unlikely to adversely affect soil or crops include calcium salts and calcium-containing soil conditioners. Specifically, calcium carbonate, calcium oxide, calcium chloride, and calcium-containing minerals such as montmorillonite can be suitably used. Furthermore, heavy calcium carbonate-containing soil conditioners and light calcium carbonate-containing soil conditioners can be suitably used as calcium-containing soil conditioners.

[0038] "Treatment method using enzyme solution" Watering from the bottom of the seedling pot, application to the surface, spraying, or spray irrigation are also possible. Furthermore, a polymer water absorbing agent may be applied simultaneously or separately. [Example]

[0039] <Adjustment of decomposing enzymes> A Pseudozyma antarctica culture solution containing PaE was prepared from Pseudozyma antarctica (accession number FERM BP-22155) using the method described in paragraph

[0021] of Patent Document 6 (hereinafter referred to as the "PaE crude enzyme solution of the present invention"), and the concentration based on the enzyme activity was measured using the method described in detail below. The solution was then adjusted with 20 mM Tris-HCl buffer (pH 8.0) to a predetermined volume of enzyme solution, and calcium carbonate (Softon) was added as needed.

[0040] <Measurement of biodegradable resin-degrading enzyme activity> The activity of the biodegradable resin-degrading enzyme was measured according to the following method for measuring the activity of the degrading enzyme described in paragraph

[0019] of Patent Document 5. First, 1730 μL of 20 mM Tris-HCl buffer (pH 6.8) and 30 μL of a substrate solution prepared by dissolving a predetermined amount of PBSA emulsion EM-301 solution in water are added to a test tube with an inner diameter of 10 mm and mixed. If necessary, 40 μL of 100 mM calcium chloride solution is added. Next, a culture solution of the microorganisms that produce the biodegradable resin-degrading enzyme is obtained, and after removing the microorganisms by centrifugation, 200 μL of the supernatant is obtained and added to the test tube. The mixture to which the supernatant has been added is stirred using a vortex mixer, and the transmittance at 660 nm is measured using a turbidimeter. The test tube is then shaken at 220 rpm at 30°C, and the transmittance is measured at the time of mixing and 15 minutes after mixing. The transmittance obtained using the turbidimeter is converted to absorbance using the following equation (1), and the enzyme activity is calculated from the obtained absorbance using the following equation (2). At=-log(X / 100) (1) C=(A0-A15)×10 / 15[U / mL / min] ···(2) (In the above formula (1), At represents the absorbance at time t (min.), and X represents the transmittance. In addition, in the above formula (2), C represents the enzyme activity, and A0 and A15 represent the absorbance at the time of mixing and 15 minutes after mixing, respectively.)

[0041] <Measurement and evaluation of test sample performance> (1) Wet tensile strength (standard), enzyme-treated tensile strength: Measurements were performed using a constant-rate extension tensile tester (Shimadzu Corporation, Autograph Tensile Tester) according to JIS P8113:1998 "Paper and paperboard - Test methods for tensile properties - Part 2: Constant-rate extension method." The sample size was 30 mm x 70 mm, and it was elongated at a chuck span of 30 mm and a tension rate of 10 mm / min, and the strength at break was measured. The same measurement was repeated eight times, and the average value (and standard deviation) was calculated. (2) Tensile strength after investment treatment: Measurements were carried out using a constant-rate extension tensile tester (Shimadzu Corporation, Autograph Tensile Tester) according to the method specified in JIS P8113:1998 "Paper and paperboard - Test methods for tensile properties - Part 2: Constant-rate extension method." The sample size was 30 mm x 70 mm, the chuck span was 30 mm, and the specimen was elongated at a tensile speed of 100 mm / min, and the strength at break was measured. The measurement was repeated four times, and the average value (and standard deviation) was calculated.

[0042] Example 1: Test on stability over time (burial test) According to Example 1, the strength and stability over time of a sample manufactured two years ago were compared with that of a sample manufactured less than one year ago. "Production of biodegradable resin composition laminated paper" Resin compositions having the blending ratios (A) to (D) and (a) to (d) shown in Table 1 below were pre-dried and then laminated to a basis weight of 84 g / m 2 By laminating the resin composition onto unbleached kraft paper (paper base material), laminated papers with two patterns of resin composition layers (lamination layers) with thicknesses of 30 μm and 15 μm were produced. Samples manufactured less than one year ago will be marked with "Code-1," and samples manufactured two years ago will be marked with "Code-2." [Table 1]

[0043] Burial test Test specimens measuring 30mm x 70mm were cut and buried in vegetable soil (our company's Super Soil, pH 6.74, EC 1.81dS / m) with a moisture content adjusted to 50%. They were then placed in an artificial climate chamber (manufactured by Nippon Medical) at a temperature of 30°C and humidity of 90%. After two weeks of storage, the samples were removed and their shapes were observed. The tensile strength of the samples was measured using an autograph tensile tester (manufactured by Shimadzu Corporation) with a chuck span of 30mm and a test speed of 100mm / min. The test was repeated four times. The strength of the samples before burial was measured by immersing the test specimens in water for 24 hours and measuring the values under the same conditions.

[0044] As shown in Figures 1 and 2, the strength after burial was stronger for the 30 μm thickness than for the 15 μm thickness, and samples (C-1), (C-2), (D-1), and (D-2), which contain 20% or more PLA, were particularly strong. Although samples (C-2) and (D-2) tended to have slightly lower strength than samples manufactured less than one year ago, they were roughly the same strength, and it was thought that deterioration over time was small. On the other hand, samples (A-2) and (B-2), which had a PLA ratio of less than 20%, were weaker than samples (C-2) and (D-2), and samples (a-2) and (b-2) were weaker than samples (c-2) and (d-2). Furthermore, the strength was lower even when compared to the strength one year after manufacture, suggesting that they are prone to deterioration over time. In any case, samples (a) and (b) or samples (A and (B) had low strength after burial and were considered to be of no practical use. Therefore, if the PLA ratio was 20% or more, sufficient strength was maintained after burial, and deterioration over time was minimal even after more than two years.

[0045] Example 2: Test on stability over time (enzyme treatment) Samples aged 2 years after production To evaluate the stability over time based on the biodegradation action of the enzyme, the physical strength of samples aged 2 years after production was measured. "Production of biodegradable resin composition laminated paper" Resin compositions having the blending ratios (A-2), (B-2), (C-2) and (D-2) shown in Table 2 below were pre-dried and then laminated to a basis weight of 84 g / m. 2The laminated paper was prepared by laminating the resin composition layer (lamination layer) to a thickness of 30 μm on unbleached kraft paper (paper base material), and the sample used was two years old after production. [Table 2]

[0046] "Enzyme solution immersion test" The crude PaE enzyme solution of the present invention was diluted with 20 mM Tris-HCl (pH 8.0) buffer to a concentration of 4.69±0.50 U / mL. The sample was cut into a 30 mm square and the weight of the sample (test piece) was measured. The sample was then immersed in the enzyme solution prepared by the method described above and shaken in an incubator (manufactured by Nippon Medical School) set at 30°C for 24 hours, after which the sample was removed and its weight was measured. The decomposition rate was calculated from the difference in weight before and after immersion. The decomposition rate of the biodegradable resin composition (also called bioplastics) alone was also estimated from the basis weight of the paper substrate.

[0047] As shown in Table 3, the decomposition rate after 24 hours was approximately 20% for (A-2), (B-2), and (C-2), while it was approximately 8% for (D-2). The decomposition rate of the biodegradable resin composition alone was approximately 70-80% for (A-2), (B-2), and (C-2), while it was approximately 30% for (D-2). When the ratio of PLA reached 30%, the progress of decomposition could be suppressed. [Table 3]

[0048] Burial test The crude PaE enzyme solution of the present invention was diluted with 20 mM Tris-HCl (pH 8.0) buffer, and calcium carbonate (Softon) was further added to a weight ratio of 2% to adjust the activity to 7.80±0.66 U / mL. Samples were cut into 30 mm x 70 mm pieces and buried in vegetable soil (our Super Soil, pH 6.74, EC 1.81 dS / m) adjusted to 50% moisture content. They were then placed in a climate chamber (manufactured by Nippon Medical) at 30°C and 90% humidity. After two and four weeks of storage, the samples were removed, their shapes were observed, and their tensile strength was measured using an autograph tensile tester (manufactured by Shimadzu Corporation) with a chuck span of 30 mm and a test speed of 10 mm / min. Enzyme-treated samples were immersed in enzyme solution for 3 hours at room temperature, as well as untreated samples immersed in water. The strength of the specimens before burying was measured by immersing the specimens in water for 12 hours under the same conditions. Tests were performed in four replicates.

[0049] As shown in Figure 3, the tensile strength after two weeks of burial in soil was (A-2) < (B-2) < (C-2) ≒ (D-2), with the sample tending to be more difficult to decompose as the PLA content increased. Four weeks after burial, the strength of (A-2) and (B-2) was lower than after two weeks, indicating that decomposition had progressed, whereas (C-2) and (D-2) maintained sufficient strength even after four weeks of burial. It should be noted that this sample was made more than two years ago, suggesting that if the sample contains more than 20% PLA, it will be less susceptible to deterioration over time. Furthermore, the tensile strength of the enzyme-treated sample was lower than that of the untreated sample, demonstrating the decomposition-promoting effect of the enzyme treatment.

[0050] Example 3: Addition test of aromatic polyester resin (enzyme treatment) <Production of biodegradable resin composition laminated paper> Resin compositions having the blending ratios (K) to (N) shown in Table 4 below were pre-dried and then subjected to corona treatment or non-corona treatment to form sheets with a basis weight of 50 g / m. 2 Laminated paper with a 30 μm thick resin composition layer (lamination layer) was produced by laminating the above unbleached kraft paper (paper base material), and samples produced less than one year ago were used. [Table 4]

[0051] "Enzyme solution immersion test" The crude PaE enzyme solution of the present invention was diluted with 20 mM Tris-HCl (pH 8.0) buffer to a concentration of 4.69±0.50 U / mL. The sample was cut into a 30 mm square and the weight of the sample (test piece) was measured. The sample was then immersed in the enzyme solution prepared by the method described above and shaken in an incubator (manufactured by Nippon Medical School) set at 30°C for 24 hours, after which the sample was removed and its weight was measured. The decomposition rate was calculated from the difference in weight before and after immersion. The decomposition rate of the biodegradable resin composition alone was also estimated from the basis weight of the paper substrate.

[0052] As shown in Table 5, the decomposition rate after 24 hours was approximately 30% for K, L, and M, and approximately 20% for N, regardless of whether or not corona treatment was performed. Furthermore, the estimated decomposition rate of only the biodegradable resin composition, excluding the paper portion, was approximately 70% for K, L, and M, and approximately 30-40% for N. The higher the PLA blend ratio, the more inhibited enzymatic decomposition was. Furthermore, in samples (L, N) containing 30% PLA, L, which contained PBAT, was more easily decomposed than N. [Table 5]

[0053] Burial test The crude PaE enzyme solution of the present invention was diluted with 20 mM Tris-HCl (pH 8.0) buffer, and calcium carbonate (Softon) was further added to a weight ratio of 2% to adjust the activity to 7.80±0.66 U / mL. Samples were cut into 30 mm x 70 mm pieces and buried in vegetable soil (our Super Soil, pH 6.74, EC 1.81 dS / m) adjusted to 50% moisture content. They were then placed in a climate chamber (manufactured by Nippon Medical) at 30°C and 90% humidity. After two and four weeks of storage, the samples were removed, their shapes were observed, and their tensile strength was measured using an autograph tensile tester (manufactured by Shimadzu Corporation) with a chuck span of 30 mm and a test speed of 10 mm / min. Enzyme-treated samples were immersed in enzyme solution for 3 hours at room temperature, as well as untreated samples immersed in water. The strength of the specimens before burying was measured by immersing the specimens in water for 12 hours under the same conditions. Tests were performed in four replicates.

[0054] As shown in Figures 4 and 5, the tensile strength of the untreated sample after 2 weeks of soil burial was <l<m<nの順で強く、plaの比率とpbatの混合の有無によって分解程度が異なった。つまり、plaの比率とpbatの混合の有無によって生分解を制御することが可能である。Furthermore, as shown in Figures 4 and 5, this tendency was more pronounced four weeks after burial. In this test, a tendency was observed for easier decomposition when part of the PBS was replaced with PBAT. The tensile strength of the enzyme-treated sample showed a similar tendency, but was lower than that of the untreated sample, confirming the effect of enzyme treatment in promoting decomposition. However, no difference in the degree of decomposition was observed due to corona discharge treatment. Furthermore, as shown in Figures 4 and 5, a certain degree of decay resistance was observed for K-1, K-2, L-1, and L-2 in a two-week burial test without enzyme treatment, but the decay resistance was extremely poor in a four-week burial test. In other words, seedling pots made from the biodegradable resin composition of K-1, K-2, L-1, and L-2 are suitable for short-term seedling raising, are quickly biodegraded after transplanting, and can reduce the generation of seedling pot residue.

Claims

1. A base paper for seedling pots is formed by laminating a biodegradable resin composition on a paper substrate having a basis weight of 30 to 100 g / m 2, and the seedling pots made of the base paper are treated with an enzyme just before planting in a field to promote decomposition. The biodegradable resin composition contains a polylactic acid resin as resin (A) and polybutylene succinate (PBS) as resin (B), the mass ratio of the resin (A) to the resin (B) is 20:80 to 30:70; The thickness of the biodegradable resin layer laminated on the paper base material is 20 to 35 μm. A seedling pot base paper characterized by:

2. A base paper for seedling pots as described in claim 1, characterized in that the resin (A) is polylactic acid.

3. A base paper for seedling pots, which is formed by laminating a biodegradable resin composition on a paper substrate, and the seedling pots made of the base paper are used in a method in which decomposition is promoted by enzymatic treatment immediately before planting in a field, The biodegradable resin composition comprises a polylactic acid-based resin as resin (A), an aliphatic polyester-based resin other than a polylactic acid-based resin as resin (B), and an aromatic polyester-based resin as resin (C); The resin (A) is contained in the range of 20 to 30% by mass relative to the total mass of the biodegradable resin composition. death, The resin (B) is contained in an amount of 55 to 72% by mass relative to the total mass of the biodegradable resin composition, The resin (C) is contained in an amount of 8 to 15% by mass relative to the total mass of the biodegradable resin composition, The base paper for seedling pots is characterized in that the thickness of the biodegradable resin layer laminated on the paper base material is 20 to 35 μm.

4. 4. The seedling pot base paper according to claim 3, wherein the resin (A) is polylactic acid.

5. 5. The seedling pot base paper according to claim 3 or 4, wherein the resin (B) is an aliphatic polyester resin obtained by polycondensation of a dicarboxylic acid component consisting of an aliphatic dicarboxylic acid and a diol component consisting of an aliphatic diol.

6. 6. The seedling pot base paper according to claim 3, wherein the resin (B) is at least one selected from the group consisting of polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and polyhydroxybutyric acid.

7. 7. The seedling pot base paper according to claim 3, wherein the resin (C) is an aromatic polyester resin obtained by polycondensation of a dicarboxylic acid component consisting of an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid and a diol component consisting of an aliphatic diol.

8. 8. The base paper for seedling pots according to any one of claims 3 to 7, wherein the resin (C) is polybutylene adipate terephthalate (PBAT).

9. A seedling pot comprising the base paper for seedling pots according to any one of claims 1 to 8.

10. A method for promoting decomposition of seedling pots, comprising the step of contacting the seedling pots of claim 9 with a biodegradable resin-decomposing enzyme to control the progress of biodegradation of the seedling pots.

11. The biodegradable resin-degrading enzyme is a biodegradable resin-degrading enzyme produced by at least one microorganism selected from the group consisting of Pseudozyma yeast, Cryptococcus yeast, Acremonium filamentous fungi, Alternaria filamentous fungi, Arthrinium filamentous fungi, Aureobasidium filamentous fungi, Cladosporium filamentous fungi, Epicoccum filamentous fungi, Fusarium filamentous fungi, Paraphoma filamentous fungi and Penicillium filamentous fungi. The method for promoting the decomposition of seedling pots according to claim 10, characterized in that the biodegradable resin-degrading enzyme is produced by at least one microorganism selected from the group consisting of Pseudozyma yeast, Cryptococcus yeast, Acremonium filamentous fungi, Alternaria filamentous fungi, Arthrinium filamentous fungi, Aureobasidium filamentous fungi, Cladosporium filamentous fungi, Epicoccum filamentous fungi, Fusarium filamentous fungi, Paraphoma filamentous fungi and Penicillium filamentous fungi.

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