Biodegradable resin sheet for fumigation

Abstract

To provide a biodegradable resin sheet for fumigation which has excellent gas barrier performance and whose sheet physical properties is less likely to be damaged even if the sheet is made thinner.SOLUTION: The invention includes 30-65 pts.mass of aliphatic aromatic polyester resin, 20-40 pts.mass of polylactic acid resin, and 10-30 pts.mass of aliphatic polyester resin with respect to 100 pts.mass of biodegradable resin, and has a thickness of 0.04-0.07 mm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a biodegradable resin sheet which uses a biodegradable resin and is preferably used as a cover sheet for fumigating pests such as pine beetles. [Background technology]

[0002] Pine-eating beetles, such as the pine spot weevil, the pine bark beetle, and the pine sawyer beetle, have traditionally caused significant damage to the growth of pine trees and remain a major cause of forest pest damage in Japan.

[0003] In order to prevent such damage from pine beetles, dead pine trees that have been damaged by pine beetles are covered and sealed with plastic barrier sheets, and then fumigated with methyl isothiocyanate (MITC) gas, an active ingredient for fumigation.In addition, even when disinfecting wood, in many cases, wood immediately after cutting is piled up outdoors, covered and sealed with plastic barrier sheets, and then fumigated with MITC gas.

[0004] Polyethylene film and polyvinyl chloride film are used as barrier sheets for such fumigation. However, fumigation of pests such as pine beetles takes a relatively long period of time, lasting for more than one month, and the fumigation barrier sheets are discarded once the chemical fumigation is completed. Chemical fumigation is often carried out in mountain forests with dead pine trees or in mountain forests where timber has been cut down, and used fumigation sheets are incinerated on site. However, in consideration of today's environmental concerns, incineration is not desirable, and therefore fumigation sheets made of biodegradable resins are increasingly being adopted.

[0005] For example, Patent Document 1 discloses a fumigation sheet made of a biodegradable aliphatic polyester resin. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-147096

[0007] Fumigation sheets are used by people who carry them on their backs to the forests where fumigation treatment is to be performed, so there is a demand for lighter sheets, such as by reducing the thickness of the sheets. However, fumigation sheets made from biodegradable resins tend to have inferior gas barrier properties compared to conventional polyethylene films and polyvinyl chloride films, and it has been necessary to make the sheets thicker to improve the gas barrier properties. On the other hand, if the sheet is made too thin, not only the gas barrier properties but also the sheet properties required for a fumigation sheet, such as tear strength, will be deteriorated. Therefore, there is a demand for lightweight sheets made from biodegradable resins while maintaining the performance required for a fumigation sheet. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to provide a biodegradable resin sheet for fumigation that has excellent gas barrier properties even when made thin and is less likely to lose its physical properties. [Means for solving the problem]

[0009] As a result of intensive research conducted by the present inventors to achieve the above object, they discovered that by incorporating an aliphatic aromatic polyester resin, a polylactic acid resin, and an aliphatic polyester resin in specific ratios, it is possible to satisfy the required performance requirements for both gas barrier properties and sheet physical properties even when the sheet is thin, and thus arrived at the present invention.

[0010] That is, the biodegradable resin sheet for fumigation of the present invention is characterized by containing, per 100 parts by mass of biodegradable resin, 30 parts by mass or more and 65 parts by mass or less of aliphatic aromatic polyester resin, 20 parts by mass or more and 40 parts by mass or less of polylactic acid resin, and 10 parts by mass or more and 30 parts by mass or less of aliphatic polyester resin, and having a thickness of 0.04 mm or more and 0.07 mm or less.

[0011] It is also preferable that the aliphatic aromatic polyester resin is polybutylene adipate terephthalate, and the aliphatic polyester resin is polybutylene succinate.

[0012] Furthermore, the methyl isothiocyanate (MITC) gas concentration measured by the following method is less than 500 ppm. (MITC gas concentration) A 380 ml plastic container is evenly filled with soil mixed with 0.14 ml of methyl isothiocyanate and 15 g of dry soil, and the container is then covered and sealed with the biodegradable fumigation resin sheet. This container is then placed in a 3.6 L plastic container with a lid and left at 24°C for 3 hours. A hole for gas measurement is pre-punched in the lid, and the hole is sealed with tape while the container is left standing. After leaving the container for 3 hours, a gas detector tube is inserted into the hole and the MITC gas concentration in the container is measured with the gas detector tube. [Effects of the Invention]

[0013] The present invention can provide a biodegradable resin sheet for fumigation that has excellent gas barrier properties even when made thin and is less likely to lose its physical properties. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is a cross-sectional view illustrating the inside of a container 1 for measuring MITC gas concentration. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention provides a biodegradable resin sheet for fumigation, which contains biodegradable resins, such as an aliphatic aromatic polyester resin, a polylactic acid resin, and an aliphatic polyester resin. The biodegradable resin is a resin that is decomposed by microorganisms in soil or water in nature over a certain period of time, ultimately decomposing into water and carbon dioxide.

[0016] The aliphatic aromatic polyester resin of the present invention is a polymerized condensation product of an aliphatic dicarboxylic acid such as succinic acid, adipic acid, suberic acid, sebacic acid, dodecanoic acid, succinic anhydride, or adipic anhydride, an aromatic dicarboxylic acid such as terephthalic acid, and an aliphatic diol. Examples of the aliphatic diol include 1,4-butanediol, 2,3-butanediol, 1,3-butanediol, 1,4-pentanediol, 2,4-pentanediol, 1,6-hexanediol, neopentyl glycol, ethylene glycol, and diethylene glycol, and one or more of these may be used.

[0017] More specifically, examples of aliphatic aromatic polyester resins include polybutylene adipate terephthalate (PBAT), polybutylene succinate terephthalate, and polytetramethylene adipate terephthalate, and among these, polybutylene adipate terephthalate (PBAT) is particularly suitable.

[0018] The polylactic acid resin of the present invention is not particularly limited as long as it is a condensation product of lactic acid (polylactic acid (PLA)), and may be poly-L-lactic acid resin, poly-D-lactic acid resin, or a mixture thereof (for example, a stereocomplex polylactic acid resin obtained by mixing poly-L-lactic acid resin and poly-D-lactic acid resin).

[0019] The aliphatic polyester resin of the present invention is a polymerized condensation product of an aliphatic dicarboxylic acid and an aliphatic diol. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanoic acid, succinic anhydride, and adipic anhydride. Two or more of these aliphatic dicarboxylic acids may be used in combination. Examples of the aliphatic diol include 1,4-butanediol, 2,3-butanediol, 1,3-butanediol, 1,4-pentanediol, 2,4-pentanediol, 1,6-hexanediol, neopentyl glycol, ethylene glycol, and diethylene glycol. One or more of these may be used.

[0020] More specifically, examples of aliphatic polyester resins include polybutylene succinate (PBS), polyethylene succinate (PES), polybutylene succinate adipate (PBSA), and the like, with polybutylene succinate (PBS) being particularly preferred.

[0021] The biodegradable resin used in the present invention may be blended with known biodegradable resins within the scope of the invention.

[0022] In the present invention, the composition contains 30 to 65 parts by mass of an aliphatic aromatic polyester resin, 20 to 40 parts by mass of a polylactic acid resin, and 10 to 30 parts by mass of an aliphatic polyester resin relative to 100 parts by mass of a biodegradable resin.

[0023] If the content of the aliphatic aromatic polyester resin is less than 30 parts by mass per 100 parts by mass of the biodegradable resin, the tear strength will be insufficient for fumigation purposes, and if it exceeds 65 parts by mass, the gas barrier properties will tend to be poor.

[0024] If the content of polylactic acid resin is less than 20 parts by mass per 100 parts by mass of biodegradable resin, the gas barrier properties will be insufficient, and if it exceeds 40 parts by mass, the resulting sheet will be too hard and difficult to stretch during fumigation work, and will be prone to breaking due to insufficient elongation.

[0025] If the content of the aliphatic polyester resin is less than 10 parts by mass per 100 parts by mass of the biodegradable resin, the gas barrier properties tend to be poor, and if it exceeds 40 parts by mass, the tear strength becomes insufficient for fumigation purposes.

[0026] The biodegradable film of the present invention can contain any additives insofar as they do not impair the effects of the present invention, such as plasticizers, heat stabilizers, lubricants, antiblocking agents, nucleating agents, biodegradation accelerators, biodegradation inhibitors, antioxidants, UV stabilizers, antibacterial agents, fillers, colorants, antistatic agents, and starch.

[0027] The biodegradable resin sheet for fumigation of the present invention is produced by molding using a commonly used method for producing a resin sheet. Examples of methods for producing such a resin sheet include T-die molding, inflation molding, and calendar molding. The sheet may be unstretched or may be uniaxially or biaxially stretched.

[0028] The thickness of the sheet of the present invention is 0.04 mm or more and 0.07 mm or less. If the sheet thickness is less than 0.04 mm, the gas barrier properties and sheet physical properties will be insufficient, and if it exceeds 0.07 mm, the burden during transportation will be great. If the sheet thickness is within this range, the labor required for transporting the sheet to the forest where fumigation treatment will be performed using a backpack or the like can be reduced. Specifically, for a sheet of the present invention measuring 4 m wide and 30 m long, if the sheet thickness is within this range, the weight of the sheet can be reduced to approximately 11 kg or less. Note that a sheet of the same size but with a thickness of 0.1 mm would weigh approximately 15 kg.

[0029] Thus, the present invention is characterized in that by containing a specific ratio of biodegradable resins, such as an aliphatic aromatic polyester resin, a polylactic acid resin, and an aliphatic polyester resin, the sheet has excellent gas barrier properties and physical properties suitable for fumigation, even if the sheet is thin, having a thickness of 0.04 mm or more and 0.07 mm or less.

[0030] In the present invention, the gas barrier property is evaluated based on the methyl isothiocyanate (MITC) gas concentration measured by the method described below. The lower the MITC gas concentration, the less gas permeates the sheet. In the present invention, the MITC gas concentration is less than 500 ppm, preferably 400 ppm or less.

[0031] [MITC gas concentration] Figure 1 shows a container 1 for measuring MITC gas concentration. A 380 ml plastic container 10 is evenly filled with soil 3, a mixture of 0.14 ml of methyl isothiocyanate (MITC, manufactured by Sankei Chemical Co., Ltd., "Kilper 40") and 15 g (approximately 20 ml) of dry soil. The container is then covered with a sheet 2 of the present invention and sealed with a frame 11. This container 10 is then placed in a 3.6 L plastic container 20 with a lid and left at 24°C for three hours. A gas measurement hole 22 is pre-opened in the lid 21, and the hole is sealed with tape 23 or the like during storage. After the container is left for three hours, a gas detector tube (not shown) is inserted into the gas measurement hole 22, and the MITC gas concentration in the container 20 is measured with the gas detector tube.

[0032] In the present invention, the physical properties of a sheet required for fumigation are evaluated based on tear strength (Elmendorf method). This is because a fumigation sheet is required to be a sheet that is difficult to tear when holes or cracks occur in the sheet due to branches or the like. The tear strength is the value obtained by dividing the tear strength (N) measured in accordance with JIS K 6732 by the thickness of the sheet, and is preferably 10 N / mm or more, more preferably 30 N / mm or more in the longitudinal direction.

[0033] The present invention is suitable for use as a fumigation sheet that can be carried on a person's back and used in forests with dead pine trees or forests where timber has been cut down, etc. It can also be used as a sheet for fumigating other coniferous trees such as pine, trees and lumber such as oak and chestnut, processed products such as pallets, cases and packaging materials, fruits, grains, soil, etc. [Example]

[0034] The present invention will be described in more detail below with reference to examples, but is not limited to these examples.

[0035] Examples 1 to 6, Comparative Examples 1 to 7, Reference Examples The components were blended in the blending ratios shown in Tables 1 and 2 below, and sheets of Examples 1 to 6, Comparative Examples 1 to 7, and Reference Example were molded by inflation molding. The blending ratios in the tables are shown in parts by mass.

[0036] The sheet thickness, MITC gas concentration, tear strength, and sheet mass of the obtained sheet were evaluated by the following methods. The results are shown in Tables 1 and 2.

[0037] [Ingredients in Tables 1 and 2] biodegradable resin PBAT: Polybutylene adipate terephthalate (BASF, "Ecoflex") PLA: Polylactic acid (manufactured by Haizheng Biotechnology Co., Ltd., "Revoda 110") PBS: Polybutylene succinate (Mitsubishi Chemical Corporation, "FZ91TN") PHBH: Polyhydroxybutyrate hexanoate (Kaneka Corporation, "X135")

[0038] [Sheet thickness] Measurement was carried out using a dial gauge with a minimum scale of 0.001 mm.

[0039] [MITC gas concentration] A measurement container 1 for MITC gas concentration, as shown in Figure 1, was used. First, a mixture of 0.14 ml of methyl isothiocyanate (MITC, manufactured by Sankei Chemical Co., Ltd., "Kilper 40") and 15 g (approximately 20 ml) of dry soil 3 was evenly spread in a 380 ml plastic container 10. The resulting sheet (10 cm wide, 10 cm long) was placed on top and pressed down with a frame 11 to seal the container. This container 10 was then placed in a 3.6 L plastic container 20 with a lid and left at 24°C for 3 hours. A gas measurement hole 22 was opened in the lid 21, and the hole 22 was covered with tape 23 during the storage period. After the container was left for 3 hours, a gas detector tube was inserted into the gas measurement hole 22, and the MITC gas concentration in the container 20 was measured using the gas detector tube. In measuring the gas concentration, a Kitagawa gas detector (manufactured by Komyo Rikagaku Kogyo Co., Ltd.) and a gas detector tube for MITC gas with a measurement range of 10 to 1500 ppm (manufactured by Komyo Rikagaku Kogyo Co., Ltd., "245UM MITC") were used.

[0040] [Tear strength: Elmendorf method] It is a value obtained by dividing the tear strength (N) in the machine direction measured in accordance with JIS K 6732 by the thickness of the sheet, and was evaluated according to the following criteria. 〇:30N / mm or more △: 10N / mm or more and less than 30N / mm ×: Less than 10N / mm

[0041] [Seat mass] The specific gravity was calculated from the mixture and converted into the mass of a sheet 4m wide and 30m long. The size of the sheet was determined based on the assumption that it would be carried by a person using a backpack to the forest where the fumigation treatment would be performed.

[0042] [Table 1]

[0043] [Table 2]

[0044] Tables 1 and 2 show that by incorporating an aliphatic aromatic polyester resin, a polylactic acid resin, and an aliphatic polyester resin in specific ratios, as in Examples 1 to 6 of the present invention, the required performance of both gas barrier properties and sheet physical properties can be satisfied even if the sheet is made thin. [Explanation of symbols]

[0045] 1 Measurement container 2 Sheet 3 Soil 10 plastic container 11 frame 20 plastic container 21 lid 22 gas measurement hole 23 tape

Claims

1. The composition contains, relative to 100 parts by mass of biodegradable resin, 30 parts by mass or more and 65 parts by mass or less of aliphatic aromatic polyester resin, 20 parts by mass or more and 40 parts by mass or less of polylactic acid resin, and 10 parts by mass or more and 30 parts by mass or less of aliphatic polyester resin, A biodegradable resin sheet for fumigation having a thickness of 0.04 mm or more and 0.07 mm or less.

2. 2. The biodegradable resin sheet for fumigation according to claim 1, wherein the aliphatic aromatic polyester resin is polybutylene adipate terephthalate, and the aliphatic polyester resin is polybutylene succinate.

3. 3. The biodegradable resin sheet for fumigation according to claim 1, wherein the methyl isothiocyanate (MITC) gas concentration measured by the following method is less than 500 ppm. (MITC gas concentration) A mixture of 0.14 ml of methyl isothiocyanate and 15 g of dry soil is spread evenly in a 380 ml plastic container, which is then covered and sealed with the biodegradable resin sheet for fumigation, and this container is then placed in a 3.6 L plastic container with a lid and left to stand for 3 hours at 24° C. A hole for gas measurement is opened in the lid in advance, and the lid is kept sealed with tape while the container is left to stand. After leaving it for 3 hours, a gas detector tube is inserted into the gas measurement hole and the MITC gas concentration in the container is measured with the gas detector tube.

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