Seedling protective cover

Abstract

The present invention aims to provide a seedling protection cover that can suppress the occurrence of tearing caused by impacts such as heavy rain and wind during the seedling protection period by improving the tear strength in the MD direction. [Solution] The invention comprises a flexible or foldable biodegradable resin sheet containing a biodegradable resin, an ultraviolet absorber, a light stabilizer, and a carbodiimide compound, wherein the biodegradable resin sheet contains 20 to 60 parts by mass of polylactic acid, 40 to 80 parts by mass of polybutylene adipate terephthalate, and 0.3 to 1.0 part by mass of the carbodiimide compound per 100 parts by mass of the biodegradable resin.

Description

Technical Field

[0001] The present invention relates to a biodegradable seedling protection cover that can prevent damage to seedlings planted in mountains and forests by wild animals and does not inhibit the growth of seedlings.

Background Art

[0002] Conventionally, as a means for preventing damage by wild animals, a method of covering seedlings with a protection cover is known. In this method, the protection cover is transported to the place where the seedlings are planted, assembled on site, and each seedling is covered with the protection cover. To prevent the protection cover from falling, it is necessary to set up supports and the like around it and tie and fix it with fixing rings and the like. As the seedling protection cover, a lightweight and easily assembled one is required. In addition, it can transmit light (light transmittance) so as not to inhibit the growth of seedlings, can withstand long-term use outdoors (weather resistance), and can also withstand impacts by animals (impact resistance). For example, sheet-shaped or net-shaped ones made of synthetic resin with light transmittance are used, and these are curved or bent into a cylindrical shape such as a cylinder or a polygonal column to protect the seedlings. For example, in Patent Document 1, a method is shown in which a transparent or translucent resin sheet is formed into a cylindrical shape with a substantially hexagonal cross section to protect seedlings, and is fixed to adjacent saplings with a well-known resin binding band.

[0003] Also, after the seedlings have grown to a certain extent, it is necessary to remove the protection cover. At that time, the used protection cover is collected, transported from the mountain, and then subjected to incineration treatment or landfill disposal. In addition, the used synthetic resin sheet has become brittle due to weathering deterioration, making it difficult to collect.

[0004]

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2001-231384 [Patent Document 2] Japanese Patent Publication No. 2013-014359 [Overview of the project] [Problems that the invention aims to solve]

[0006] Further investigation by the inventors revealed that when the seedling protection cover is folded into a polygonal shape to maintain its cylindrical shape, as shown in Figure 1, there is a risk that the cover may tear at the folds 5 (for example, like a banana peel) during the seedling protection period due to severe weather such as heavy rain and wind, as shown in Figure 2. The inventors believe that the reason for this is that when the folds are made in the direction of flow (MD) of the sheet used for the seedling protection cover, the tear strength of the folds weakens, making them more susceptible to tearing from impacts such as heavy rain and wind. If tears occur during the protection period, there is a concern that the protective cover may collapse, the seedlings may be exposed, and damage from animals may occur.

[0007] In other words, the present invention aims to provide a seedling protection cover that can suppress the occurrence of tearing caused by impacts such as heavy rain and wind during the seedling protection period by improving the tear strength in the MD direction. [Means for solving the problem]

[0008] The present invention comprises a bendable or foldable biodegradable resin sheet containing a biodegradable resin, an ultraviolet absorber, a light stabilizer, and a carbodiimide compound, wherein the biodegradable resin sheet contains 20 to 60 parts by mass of polylactic acid, 40 to 80 parts by mass of polybutylene adipate terephthalate, and 0.3 to 1.0 part by mass of the carbodiimide compound per 100 parts by mass of the biodegradable resin.

[0009] Preferably, the tear strength of the biodegradable resin sheet in the flow direction (MD) is 35 N / mm or more and 200 N / mm or less.

[0010] Preferably, the tear strength of the biodegradable resin sheet in the width direction (TD) is 35 N / mm or more and 200 N / mm or less. [Effects of the Invention]

[0011] The present invention makes it possible to provide a seedling protection cover that can suppress the occurrence of cracking caused by impacts such as heavy rain and wind during the seedling protection period. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view showing an example of how to use a seedling protective cover. [Figure 2] This diagram shows a seedling protective cover that has torn at the fold. [Modes for carrying out the invention]

[0013] The present invention relates to a seedling protective cover made of a curved or foldable biodegradable resin sheet containing a biodegradable resin, an ultraviolet absorber, a light stabilizer, and a carbodiimide compound.

[0014] [Polylactic acid] The biodegradable resin sheet comprising the present invention requires polylactic acid as the biodegradable resin, and contains 20 to 60 parts by mass of polylactic acid per 100 parts by mass of biodegradable resin. If the polylactic acid content is less than 20 parts by mass, the sheet tends to be too soft and will not stand upright even when formed into a cylinder. On the other hand, if the polylactic acid content exceeds 60 parts by mass, the sheet becomes difficult to bend or fold, making it difficult to process, and its tear strength also weakens.

[0015] In the present invention, the biodegradable resin sheet preferably contains 30 to 50 parts by mass of polylactic acid per 100 parts by mass of biodegradable resin. When the polylactic acid content is within this range, it has appropriate flexibility, the sheet can stand upright in a cylindrical shape, and the assembly of the seedling protective cover becomes easier.

[0016] [Polybutylene adipate terephthalate] The biodegradable resin sheet comprising the present invention further requires polybutylene adipate terephthalate as the biodegradable resin, and contains 40 to 80 parts by mass of polybutylene adipate terephthalate per 100 parts by mass of biodegradable resin. If the polybutylene adipate terephthalate content is less than 40 parts by mass, the tear strength is weak, making it easily torn by rain and wind, and it is unsuitable as a seedling protective cover. On the other hand, if the polybutylene adipate terephthalate content exceeds 80 parts by mass, it becomes a highly elastic sheet, making it difficult to stand upright when used as a seedling protective cover.

[0017] In the present invention, the biodegradable resin sheet preferably contains 50 to 70 parts by mass of polybutylene adipate terephthalate per 100 parts by mass of biodegradable resin. When the polybutylene adipate terephthalate content is within this range, it has appropriate flexibility, the sheet can stand upright in a cylindrical shape, and the assembly of the seedling protective cover is made easy.

[0018] [Carbodiimide compounds] The biodegradable resin sheet constituting the present invention requires the addition of a carbodiimide compound. Conventionally known carbodiimide compounds can be used in the present invention. For example, a monocarboxydiimide compound having one carbodiimide group in the same molecule, a polycarbodiimide compound having two or more carbodiimide groups in the same molecule can be mentioned. Furthermore, an aromatic monocarboxydiimide compound or an aromatic polycarbodiimide compound containing an aromatic ring in the molecule, an aliphatic monocarboxydiimide compound or an aliphatic polycarbodiimide compound not containing an aromatic ring in the molecule, etc. can be mentioned. Among these, any one of them can be used alone, or two or more of them can be used in combination. Among them, aliphatic monocarboxydiimide compounds and aliphatic polycarbodiimide compounds are preferably used.

[0019] Examples of the aliphatic monocarboxydiimide compound include dicyclohexylcarbodiimide, ethylene bis(dicyclohexylcarbodiimide), hexamethylene bis(dicyclohexylcarbodiimide), diisopropylcarbodiimide, N-ethyl-N'-(3-dimethylaminopropyl)carbodiimide, etc. Further, as the aliphatic polycarbodiimide compound, it can be synthesized by a decarboxylation condensation reaction of diisocyanate using a carbodiimidization catalyst such as an organic phosphorus compound or an organometallic compound. Examples of the diisocyanate include hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, xylylene diisocyanate, tetramethylxylylene diisocyanate, etc.

[0020] The strength of the resin sheet is affected by the temperature conditions during molding, the extrusion speed, and the compatibility of the resin. Generally, the resin sheet is oriented by being stretched during molding. However, if the resin viscosity is low, that is, if the fluidity of the resin is high, the orientation progresses rapidly, and the tear strength in the stretching direction tends to weaken. In the present invention, when a carbodiimide compound is added to the biodegradable resin, the compatibility of the biodegradable resin is improved, and a crosslinking reaction occurs in the resin of the sheet, increasing the viscosity. When the viscosity of the resin is high, the fluidity of the resin decreases, and the resin sheet is slowly extruded while being heated. In other words, it is considered that the tear strength in the MD direction of the biodegradable resin sheet of the present invention is improved by suppressing the orientation in the flow direction (MD direction).

[0021] The carbodiimide compound contains 0.3 parts by mass or more and 1.0 part by mass or less with respect to 100 parts by mass of the biodegradable resin. If the content of the carbodiimide compound is less than 0.3 parts by mass, sufficient tear strength in the MD direction cannot be obtained as a seedling protection cover, and there is a risk of tearing. On the other hand, if the content of the carbodiimide compound exceeds 1.0 part by mass, the viscosity becomes excessively high during sheet production, the fluidity decreases, and it becomes difficult to perform extrusion molding.

[0022] In the present invention, as the biodegradable resin sheet, preferably, the content of the carbodiimide compound when 100 parts by mass of the biodegradable resin is 0.5 parts by mass or more and 0.7 parts by mass or less. If the content of the carbodiimide compound is within this range, it has sufficient tear strength as a seedling protection cover, has good processability, and also leads to a reduction in manufacturing cost by minimizing the use of raw materials.

[0023] Since the seedling protection cover is used until the seedlings grow to a certain extent, weather resistance is required, and in the present invention, it contains an ultraviolet absorber and a light stabilizer.

[0024] [Ultraviolet absorber][[ID=Examples of UV absorbers include salicylic acid esters, benzotriazoles, hydroxybenzophenones, and acrylonitrile-substituted compounds. These UV absorbers can be used individually or in combination of two or more. Specifically, 2-hydroxybenzophenones such as 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-ethoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 5,5'-methylenebis(2-hydroxy-4-methoxybenzophenone); 2-(2'-hydroxy-5'-methylphenyl)benzotriazoles such as 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole, and 2,2'-methylenebis(4-tert-octyl-6-benzotriazole)phenol; phenyl salicylate, resorcinol monobenzoate, and 2,4-di-t Examples include benzoates such as ert-butylphenyl-3',5'-di-tert-4'-hydroxybenzoate and hexadecyl-3,5-di-tert-butyl-4-hydroxybenzoate; oxanilides such as 2-ethoxy-4'-dodecyloxanilide; and cyanoacrylates such as ethyl-α-cyano-β,β-diphenyl acrylate and methyl-2-cyano-3-methyl-3-(p-methoxyphenyl)acrylate.

[0025] [Light stabilizer] Examples of light stabilizers include hindered amine-based light stabilizers, specifically 2,2,6,6-tetramethyl-4-pyridyl stearate, 1,2,2,6,6-pentamethyl-4-pyridyl stearate, 2,2,6,6-tetramethyl-4-pyridylbenzoate, N-(2,2,6,6-tetramethyl-4-pyridyl)dodecylsuccinimide, 1-[(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxyethyl]-2,2,6,6-tetramethyl-4-piperidyl(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, and bis(1,2,2,6,6-pentamethyl-4-pyridyl) -2-butyl-2-(3,5-di-tert-butyl-4-hydroxybenzyl)malonate, N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine, tetra(2,2,6,6-tetramethyl-4-piperidyl)butanetetracarboxylate, bis(2,2,6,6-tetramethyl-4-piperidyl)di(tridecyl)butanetetracarboxylate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)di(tridecyl)butanetetracarboxylate, 3,9-bis{1,1- Dimethyl-2-[tris(2,2,6,6-tetramethyl-4-piperidyloxycarbonyloxy)butylcarbonyloxy]ethyl}-2,4,8,10-tetraoxaspiro[5.5]undecane, 3,9-bis{1,1-dimethyl-2-[tris(1,2,2,6,6-pentamethyl-4-piperidyloxycarbonyloxy)butylcarbonyloxy]ethyl}-2,4,8,10-tetraoxaspiro[5.Examples of hindered amine-based light stabilizers include undecane, 1,5,8,12-tetrakis{4,6-bis[N-(2,2,6,6-tetramethyl-4-piperidyl)butylamino]-1,3,5-triazine-2-yl}-1,5,8,12-tetraazadodecane, 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol / dimethyl succinate condensate, 2-tert-octylamino-4,6-dichloro-s-triazine / N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine condensate, and N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine / dibromoethane condensate.

[0026] The amount of these UV absorbers and light stabilizers should be 0.1 to 1 part by mass each per 100 parts by mass of biodegradable resin. If the amount is less than 0.1 parts by mass, no effect will be obtained, and if it exceeds 1 part by mass, no further effect will be observed, and it will not only increase costs but also impair the light transmittance of the plant seedling protective cover due to bloom, which is undesirable.

[0027] [Other additives] The present invention may be modified by adding various additives as needed, provided that its physical properties are not impaired. Examples of additives include antioxidants, antistatic agents, lubricants, inorganic fillers, organic fillers, pigments, plasticizers, antifogging agents, and flame retardants.

[0028] [Physical properties] The present invention relates to a seedling protection cover made of a curved or foldable biodegradable resin sheet containing a biodegradable resin, an ultraviolet absorber, a light stabilizer, and a carbodiimide compound, and having a tear strength suitable for protecting seedlings. Specifically, the biodegradable resin sheet of the present invention preferably has a tear strength in the flow direction (MD) of the biodegradable resin sheet of 35 N / mm or more and 200 N / mm or less, and further preferably has a tear strength in the width direction (TD) of the biodegradable resin sheet of 35 N / mm or more and 200 N / mm or less. The following describes in detail the physical properties of the biodegradable resin sheet used in the seedling protection cover of the present invention.

[0029] [Tear strength] The biodegradable resin sheet of the present invention preferably has a tear strength in the flow direction (MD) of the biodegradable resin sheet of 35 N / mm or more and 200 N / mm or less. Generally, in sheets manufactured by extruders, the resin is oriented in the flow direction (MD) during extrusion, resulting in different tear strengths in the MD and TD directions, with a tendency for the tear strength to be particularly weak in the MD direction. Furthermore, in sheets used for protecting seedlings, the MD direction may be the longitudinal direction of the seedling protection cover product in order to obtain the necessary height for protecting the seedlings. In that case, if the tear strength in the MD direction is weak, when the sheet is curved or folded into a tube shape for seedling protection, there is a risk that tears may occur at points with inferior tear strength, such as the fold 5, during the protection period, as shown in Figure 2. This invention improves the compatibility of the resin and increases its viscosity by adding a carbodiimide compound, thereby suppressing the orientation of the resin in the MD direction, and resulting in a tear strength in the MD direction of 35 N / mm to 200 N / mm. A tear strength of 35 N / mm to 200 N / mm in the MD direction improves the longitudinal strength of the seedling protection cover, preventing tearing during the protection period even when used in a curved or folded position.

[0030] The biodegradable resin sheet of the present invention preferably has a tear strength in the width direction (TD) of the biodegradable resin sheet of 35 N / mm or more and 200 N / mm or less. This configuration makes it possible to obtain a biodegradable resin sheet with more suitable tear strength for use as a seedling protective cover. Furthermore, regardless of whether the MD direction or the TD direction is the longitudinal direction of the seedling protective cover product, it is possible to suppress the occurrence of tearing during the protection period.

[0031] The tear strength of the above-mentioned biodegradable resin sheet is measured in accordance with JIS K7128.

[0032] [Seedling protective cover] The seedling protection cover of the present invention may vary depending on the size of the seedling to be protected, but the height is preferably in the range of 100 to 200 cm and the width is preferably in the range of 30 to 80 cm. Furthermore, the thickness is preferably 0.1 to 2.0 mm. If it is too thick, the light transmission will decrease, which may inhibit the growth of the seedlings, and the weight will increase, making transportation and handling difficult. If it is too thin, the sheet will not be able to stand on its own, making it difficult to handle, and its weather resistance will decrease, causing it to crack before the seedlings have a chance to grow due to prolonged exposure.

[0033] Furthermore, the seedling protective cover of the present invention may be provided with multiple locking parts or other annular bodies (such as rings) at both ends of the biodegradable resin sheet, which are capable of maintaining the cylindrical shape formed by the curvature or bending of the sheet. The shape of the locking parts is not particularly limited as long as they can lock both ends of the sheet, but for example, a notch can be provided at one end and a notch for insertion into the notch can be provided at the other end opposite to it. Alternatively, through holes can be provided in addition to notches. Two to five pairs of such locking parts are sufficient for one sheet. Furthermore, the cross-sectional shape of the cylindrical body may be a known shape such as a circle or a polygon.

[0034] The locking portion of the seedling protection cover of the present invention may be designed to allow the support post to pass through. Therefore, since a separate support post fixing device is not required, assembly is simplified. The support post is not particularly limited as long as it is used as a support post for fixing the seedling protection cover.

[0035] The seedling protection cover of the present invention may be provided with multiple ventilation holes. These ventilation holes facilitate the flow of air into the cover, which is beneficial for the growth of the seedlings.

[0036] The lower end of the seedling protection cover of the present invention can be provided with a hole for inserting a retaining stake. The retaining stake is used to fix the seedling protection cover to the ground, and since the cylindrical body does not rotate even when exposed to wind, it is possible to prevent damage to the branches and leaves of the seedling caused by the rotation of the cylindrical body.

[0037] The seedling protective cover of the present invention is formed by punching out a biodegradable resin sheet molded by methods such as the T-die method, calendering method, or inflation method, but the T-die method is particularly preferred from the viewpoint of ensuring the sheet has the necessary thickness to stand on its own.

[0038] As shown in Figure 1, the seedling protection cover of the present invention is transported in sheet form to the forest or other area where the seedlings are planted, and assembled there. The assembly method involves first rolling the seedling protection cover 1 into a cylindrical or polygonal shape and securing it with a fixing ring 3. Next, a support pole 2 is attached to the seedling protection cover 1. Then, the cover is placed over the seedling, and the support pole 2 is driven into the ground about 40-50 cm to secure the seedling protection cover to the ground. [Examples]

[0039] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0040] [Example 1] 40 parts by mass of PLA, 60 parts by mass of PBAT, 0.3 parts by mass of carbodiimide compound, 1.5 parts by mass of talc, 0.85 parts by mass of UVA, and 0.5 parts by mass of HALS were mixed and a film was formed using a T-die extruder to obtain a sheet with a thickness of 0.5 mm. The composition is shown in Table 1. Note that Table 1 is listed in parts by mass and shows the amount of each compound relative to 100 parts by mass of biodegradable resin.

[0041] [Examples 2-8] Sheets were obtained in the same manner as in Example 1, except that the formulation amounts were changed as shown in Table 1.

[0042] [Comparative Examples 1-5] Sheets were obtained in the same manner as in Example 1, except that the formulation amounts were changed as shown in Table 1.

[0043] [Resin composition] biodegradable resin PLA: Polylactic acid (manufactured by Kaisei Biomaterials Co., Ltd., product name "REVODE110") PBAT: Polybutylene adipate terephthalate (BASF product name "Ecoflex C1200") additives Inorganic filler talc: (Manufactured by Takehara Chemical Industry Co., Ltd., product name "Hytron") UV absorber: UVA (Manufactured by Chemipro Chemical Co., Ltd., product name "KEMISORB12") Light stabilizer: HALS (ADEKA Corporation, product name "ADEKA Stab LA-63FL") Carbodiimide compound: (Manufactured by Nisshinbo Chemical Co., Ltd., product name "Carbodilite LA-1")

[0044] [Tear test] For the sheets obtained in Examples 1-8 and Comparative Examples 1, 2, 4, and 5, the tear strength (N / mm) in the MD and TD directions was measured using a Trouser tear tester (manufactured by A&D Company, Limited, product name "Tensilon RTF-1310") at a test speed of 200 mm / min and room temperature, in accordance with JIS K 7128-1. The results are shown in Table 1. Comparative Example 3 was not measured because it could not be molded.

[0045] [Practicality] The sheets obtained in Examples 1-8 and Comparative Examples 1, 2, 4, and 5 were cut to a height of 1425 mm and a width of 360 mm, and their workability was evaluated when assembled as shown in Figure 1 using the following procedure. The results are shown in Table 1. Procedure (1) Roll up seedling protective cover 1 into a roughly hexagonal shape. (2) Secure the seedling protective cover 1 with the fixing ring 3. (3) Pass the support post 2 through the fixing ring 3 from the upper end of the seedling protection cover 1. (4) Place the support stake 2 over the seedling in the state described in (3), and insert it into the soil about 40-50 cm deep. The evaluation criteria are as follows: ○: The seat can stand on its own during assembly and does not detach from the fixing ring 3. △: The seat is difficult to stand upright during assembly, but it does not detach from the fixing ring 3. ×: The seat cannot stand on its own during assembly, and it detaches from the fixing ring 3.

[0046] [Weather resistance] The sheets obtained in Example 3 and Comparative Example 1 were subjected to weathering tests for 500 hours using a weathering tester (manufactured by Suga Test Instruments Co., Ltd., product name "Sunshine Weather S80") in accordance with JIS K 6732. Subsequently, the tear strength (N / mm) in the MD direction was measured using a trouser tear tester (manufactured by A&D Company, Limited, product name "Tensilon RTF-1310") at a test speed of 200 mm / min and at room temperature, in accordance with JIS K 7128-1. Trouser tear was measured using a sample from before the weathering test as a blank. The results are shown in Table 2.

[0047] [Table 1]

[0048] [Table 2]

[0049] Examples 1 to 8 demonstrate that adding a carbodiimide compound increases the tear strength in the MD direction to 35 N / mm or higher, indicating an improvement in tear strength in the MD direction.

[0050] Table 2 shows that, when exposed for the same amount of time, Example 3, which had a carbodiimide compound added, was more resistant to tearing than Comparative Example 1, which did not have a carbodiimide compound added. This demonstrates that the sheet of the present invention improves tear strength in the MD direction, thereby suppressing tearing caused by impacts such as heavy rain and wind during the seedling protection period. [Explanation of Symbols]

[0051] 1. Seedling protective cover 2 pillars 3. Fixing ring 4 Seedlings 5. Folded section

Claims

1. It consists of a flexible or foldable biodegradable resin sheet containing a biodegradable resin, an ultraviolet absorber, a light stabilizer, and a carbodiimide compound. The biodegradable resin sheet is characterized by containing 20 to 60 parts by mass of polylactic acid and 40 to 80 parts by mass of polybutylene adipate terephthalate per 100 parts by mass of the biodegradable resin, and containing 0.3 to 1.0 part by mass of a carbodiimide compound per 100 parts by mass of the biodegradable resin, as a seedling protective cover.

2. The seedling protection cover according to claim 1, characterized in that the tear strength of the biodegradable resin sheet in the flow direction (MD) is 35 N / mm or more and 200 N / mm or less.

3. The seedling protection cover according to claim 1, characterized in that the tear strength in the width direction (TD) of the biodegradable resin sheet is 35 N / mm or more and 200 N / mm or less.

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