Biodegradable mulch film

Abstract

A biodegradable mulch film comprises: a colored layer group 2 containing an aliphatic polyester and colorants; and a tear-preventing layer containing an aromatic aliphatic polyester. The colored layer group 2 includes a white layer 3 containing a white pigment as a colorant, and a black layer 4 containing a black pigment as a colorant. The amount of the aliphatic polyester contained in the colored layer group 2 is 10-30 mass% based on resins.

Description

Biodegradable Multifilm

[0001] The present invention relates to a biodegradable multifilm.

[0002] As a covering material for covering ridges for growing crops, an agricultural multifilm is known. The agricultural multifilm is used for the purpose of promoting stable growth of crops by ensuring heat retention of the soil, suppressing weeds, suppressing evaporation of moisture, and the like.

[0003] By the way, as an agricultural multifilm, a film having biodegradability (hereinafter referred to as "biodegradable multifilm") may be used for the purpose of omitting collection and disposal after use and reducing the burden on the user. As such a biodegradable multifilm, a multifilm having a white layer and a black layer (so-called black-and-white multifilm) is known.

[0004] In relation to the above, Patent Document 1 (Japanese Patent Application Laid-Open No. 2019-55485) discloses a biodegradable resin film provided with a reflective layer and a colored layer, wherein the reflective layer is composed of a resin composition containing a biodegradable aliphatic aromatic polyester resin and titanium oxide, and the colored layer is composed of a resin composition containing a biodegradable aliphatic aromatic polyester resin and carbon black. According to the invention of Patent Document 1, the biodegradable resin film is biodegraded after use, for example, by plowing it into the soil together with the soil.

[0005] The present inventors have been considering using an aliphatic polyester such as PBS (polybutylene succinate) in the black-and-white multifilm. By using an aliphatic polyester, benefits can be obtained in terms of easy biodegradability, moldability, mechanical properties, and short-term weather resistance.

[0006] However, when an aliphatic polyester is used, the film may be easily torn. If tearing occurs during use as a covering material, the original function of promoting the growth of crops is inhibited.

[0007] Therefore, an object of the present invention is to provide a biodegradable multifilm that has an aliphatic polyester and can suppress the occurrence of tearing.

[0008] A biodegradable mulch film according to one aspect of the present invention comprises a group of colored layers containing an aliphatic polyester and a colorant, and a tear-resistant layer containing an aromatic aliphatic polyester. The group of colored layers includes a white layer containing a white pigment as a colorant and a black layer containing a black pigment as a colorant. The aliphatic polyester content in the group of colored layers is 10% by mass or more and 30% by mass or less, based on the resin.

[0009] According to the present invention, a biodegradable mulch film is provided that contains aliphatic polyester while suppressing the occurrence of tearing.

[0010] Figure 1 is a schematic cross-sectional view illustrating the biodegradable mulch film according to this embodiment. Figure 2 is a schematic cross-sectional view illustrating a modified biodegradable mulch film.

[0011] Embodiments of the present invention will be described below with reference to the drawings.

[0012] Figure 1 is a schematic cross-sectional view illustrating the biodegradable mulch film 1 according to this embodiment. As shown in Figure 1, the biodegradable mulch film 1 comprises a colored layer group 2 and an outer layer 5 and an inner layer 6 arranged to sandwich the colored layer group 2. The colored layer group 2 contains aliphatic polyester and a coloring agent. The outer layer 5 and inner layer 6 function as tear-resistant layers and contain aromatic aliphatic polyester. The biodegradable mulch film 1 is used in the agricultural field, for example, as a covering material to cover ridges where crops are grown. When using the biodegradable mulch film 1, the side exposed to sunlight is the outer layer 5, and the side facing the soil is the inner layer 6.

[0013] The colored layer group 2 has a white layer 3 containing a white pigment as a coloring agent and a black layer 4 containing a black pigment as a coloring agent. In other words, the biodegradable mulch film 1 is a so-called black and white mulch film.

[0014] The aliphatic polyester content in colored layer group 2 is 10% by mass or more and 30% by mass or less, based on the resin. In this specification, "content based on resin" refers to the content of each resin when the total mass of the resin components is taken as 100% by mass. In other words, colored layer group 2 also contains resin components other than aliphatic polyester, and aliphatic polyester is only a part of the resin components.

[0015] According to the above configuration, a biodegradable mulch film 1 is provided that contains aliphatic polyester while suppressing the occurrence of film tearing. As previously described, when aliphatic polyester is included in the colored layer group 2, the film may become prone to tearing along its molding direction (MD direction). In contrast, according to this embodiment, an outer layer 5 and an inner layer 6 are provided so as to sandwich the colored layer group 2, and the outer layer 5 and inner layer 6 contain aromatic aliphatic polyester. By providing such an outer layer 5 and inner layer 6, the occurrence of film tearing can be suppressed.

[0016] In addition, according to this embodiment, since the aliphatic polyester content in the colored layer group 2 is 30% by mass or less based on the resin, the occurrence of film tearing can be suppressed more reliably.

[0017] The above is an overview of this embodiment. Next, the detailed configurations of the colored layer group 2, the outer layer 5, and the inner layer 6 will be described.

[0018] <Colored Layer Group> As previously described, colored layer group 2 has a white layer 3 and a black layer 4. The white layer 3 is located on the outside, and the black layer 4 is located on the inside. In each layer included in colored layer group 2, the coloring agent is dispersed in the resin component.

[0019] The resin content in the colored layer group 2 is, for example, 50% by mass or more, preferably 70% by mass or more, based on the total mass of the colored layer group 2. The resin content may differ between the white layer 3 and the black layer 4. In this case, the resin content in the colored layer group 2 is based on the total mass of the colored layer group 2. For example, even if the resin content in the white layer 3 is less than 50% by mass, depending on the resin content in the black layer 4, the total resin content in the colored layer group 2 may be 50% by mass or more. This also applies to the content of the other components described below.

[0020] (Aliphatic Polyester) The colored layer group 2 contains an aliphatic polyester. By using an aliphatic polyester, the biodegradability, moldability, mechanical properties, and short-term weather resistance of the film can be improved. In this specification, "aliphatic polyester" means polyester that does not have repeating units containing aromatics. Therefore, "aromatic aliphatic polyester" is not included in "aliphatic polyester" as defined herein.

[0021] Examples of aliphatic polyesters include at least one selected from the group consisting of polylactic acid (PLA), polyhydroxyalkanoic acid (PHA), polybutylene succinate adipate (PBSA), polycaprolactone (PCL), polyglycolic acid (PGA), polyethylene adipate, polybutylene adipate, polyhydroxyadipate, polycyclohexylene dimethyl adipate, and compounds containing repeating units represented by the following formula (A) (hereinafter referred to as "aliphatic polyester A").

[0022] (Note that in the above formula (A), m1 and m2 are integers between 1 and 4.)

[0023] Preferably, the aliphatic polyester includes the aliphatic polyester A and / or polyhydroxyalkanoic acid described above. Examples of compounds corresponding to aliphatic polyester A include polybutylene succinate (PBS) and polyethylene succinate (PES), with PBS being more preferred from the viewpoint of biodegradability. As for PBS, plant-derived (biomass-derived) products are available commercially. Using plant-derived PBS is also preferable from the viewpoint of environmental impact. Examples of polyhydroxyalkanoic acid include polyhydroxybutyrate (PHB) and 3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH).

[0024] The aliphatic polyester content in the colored layer group 2 is 10% to 30% by mass, based on the resin. More preferably, the aliphatic polyester content in the colored layer group 2 is 15% to 25% by mass, based on the resin.

[0025] If the aliphatic polyester content in colored layer group 2 is too high, the film is more prone to tearing along the molding direction. In contrast, if the aliphatic polyester content in colored layer group 2 is 30% by mass or less based on the resin, the occurrence of tearing can be sufficiently suppressed.

[0026] Furthermore, if the aliphatic polyester content in the colored layer group 2 is 10% by mass or more based on the resin, the advantageous effects of aliphatic polyester in terms of easy biodegradability, moldability, mechanical properties, and short-term weather resistance can be fully realized.

[0027] (Aromatic Aliphatic Polyester) As a resin component other than aliphatic polyester that may be included in the colored layer group 2, aromatic aliphatic polyester is preferred. Aromatic aliphatic polyester has excellent stretchability. Blending aromatic aliphatic polyester can more reliably suppress the occurrence of film tearing. In this specification, "aromatic aliphatic polyester" refers to a polyester having both repeating units having aroma and repeating units without aroma.

[0028] Aromatic aliphatic polyesters are not particularly limited. Examples of aromatic aliphatic polyesters include compounds having two types of repeating units represented by the following formula (B) (hereinafter referred to as "aromatic aliphatic polyester B").

[0029] (In formula (B) above, n1 and n2 represent the molar amounts of each repeating unit. The molar ratio (n1:n2) is, for example, 0.3:1.0 to 10:1.0. Preferably, the molar ratio (n1:n2) is 1.0:1.0 to 1.3:1.0. Also, m3, m4, and m5 are integers from 1 to 4. Furthermore, R is a substituent, representing a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.)

[0030] Preferably, as aromatic aliphatic polyester B, polybutylene adipate terephthalate (PBAT) and polybutylene succinate terephthalate (PBST) are used. Compared to PBAT, PBST has a higher ability to suppress photodegradation. Biodegradable mulch films, for example, may become prone to cracking due to photodegradation if exposed to sunlight for a long period of time while used as a covering material. In contrast, if PBST is included in the colored layer group 2, the progression of photodegradation can be efficiently suppressed, and the occurrence of cracking can be suppressed more reliably. Furthermore, plant-derived PBST is commercially available. By using plant-derived PBST, the environmental burden can be reduced.

[0031] The aromatic aliphatic polyester content in the colored layer group 2 is, for example, 70% by mass or more, preferably 80% by mass or more, based on the resin.

[0032] (White layer) Next, we will explain the white layer 3 included in the colored layer group 2. As previously mentioned, the white layer 3 contains white pigment. The white pigment is a particle with reflectivity.

[0033] While there are no particular limitations on the white pigment, titanium dioxide is preferred due to its extremely high reflectivity.

[0034] The content of the white pigment in the white layer 3 is, for example, 15% to 40% by mass, preferably 20% to 30% by mass, based on 100% by mass of the total mass of the white layer.

[0035] The thickness of the white layer 3 is, for example, 1 to 20 μm, preferably 3 to 12 μm.

[0036] (Black layer) Next, we will explain black layer 4. As previously mentioned, black layer 4 contains black pigment. The black pigment is a light-shielding particle.

[0037] Examples of black pigments include carbon black, titanium black, acetylene black, lamp black, graphite, aniline black, cyanine black, and perylene black. In particular, it is preferable to include carbon black because of its extremely high light-shielding properties.

[0038] The content of black pigment in the black layer 4 is, for example, 1 to 15% by mass, preferably 3 to 10% by mass, based on 100% by mass of the total mass of the black layer.

[0039] The thickness of the black layer 4 is, for example, 1 to 10 μm, preferably 1 to 5 μm.

[0040] (Total thickness of colored layer group 2) The total thickness of colored layer group 2, including the white layer 3 and the black layer 4, is, for example, 5 to 20 μm, preferably 10 to 15 μm.

[0041] (Other Additives) The colored layer group 2 may also contain other additives as needed. Examples of other additives include decomposition accelerators, lubricants, weathering agents, slip agents, heat insulating materials, antiblocking agents, plasticizers, film-forming aids, thickeners, pigment dispersants, and heat stabilizers and hydrolysis inhibitors.

[0042] (Decomposition accelerator) Preferably, the colored layer group 2 contains a decomposition accelerator. The inclusion of the decomposition accelerator promotes the breakdown of the colored layer group 2, thereby improving biodegradability. The decomposition accelerator is not particularly limited, but calcium carbonate is preferred because it can efficiently promote decomposition.

[0043] The content of the decomposition accelerator in the colored layer group 2 is, based on the mass of the entire colored layer group 2, for example, 1% by mass to 20% by mass, preferably 5% by mass to 15% by mass.

[0044] <Outer layer and inner layer> As described above, the outer layer 5 and the inner layer 6 that form the surface layer of the biodegradable multilayer film 1 contain an aromatic aliphatic polyester.

[0045] Examples of the aromatic aliphatic polyester used for the outer layer 5 and the inner layer 6 include the same ones as those described in the colored layer group 2.

[0046] The content of the aromatic aliphatic polyester in each of the outer layer 5 and the inner layer 6 is, taking the total mass of each layer as 100%, for example, 80% by mass or more, preferably 90% by mass or more.

[0047] Preferably, examples of the aromatic aliphatic polyester include PBAT (polybutylene adipate terephthalate) and PBST (polybutylene succinate terephthalate). By using these polyesters, the occurrence of film tearing can be sufficiently suppressed.

[0048] More preferably, both PBAT and PBST are included as the aromatic aliphatic polyester in the outer layer 5 and the inner layer 6. Here, the content of PBST is preferably more than the content of PBAT. Thereby, the occurrence of film tearing can be more reliably suppressed. Most preferably, the content of PBST is 70% by mass or more when the total amount of the aromatic aliphatic polyester contained in each layer is 100% by mass.

[0049] The thickness of the outer layer 5 and the inner layer 6 is, for example, 0.5 to 10 μm, preferably 1 to 5 μm.

[0050] Furthermore, the outer layer 5 and inner layer 6 may contain other additives as needed. Examples of other additives include lubricants, weathering agents, slip agents, heat insulating materials, antiblocking agents, plasticizers, film-forming aids, thickeners, and heat stabilizers and hydrolysis inhibitors. However, if the outer layer 5 and inner layer 6 decompose during use as a coating material, sufficient effectiveness in suppressing crack formation may not be obtained. From this viewpoint, it is preferable that inorganic pigments and decomposition accelerators are not included.

[0051] The content of components other than aromatic aliphatic polyester in the outer layer 5 and inner layer 6 is, for example, 20% by mass or less, and preferably 10% by mass or less.

[0052] (Modified version of colored layer group 2) Next, a modified version of colored layer group 2 will be described. Figure 2 is a schematic cross-sectional view showing this modified version. In this modified version, colored layer group 2 includes a fully aromatic aliphatic polyester layer. A fully aromatic aliphatic polyester layer is a resin layer whose resin component is made of aromatic aliphatic polyester. That is, it is a layer in which 100% by mass of the resin component is aromatic aliphatic polyester.

[0053] The above configuration provides a biodegradable mulch film 1 that can more reliably suppress the occurrence of film tearing. That is, as previously described, aromatic aliphatic polyester has high elongation properties. Therefore, by including a layer made of aromatic aliphatic polyester as the resin component in the colored layer group 2, the occurrence of tearing is more reliably suppressed.

[0054] Preferably, the fully aromatic aliphatic polyester layer is provided in a part of the white layer 3. That is, as shown in Figure 2, the white layer 3 includes a first white layer 3-1 and a second white layer 3-2. The first white layer 3-1 is positioned between the second white layer 3-2 and the black layer 4. That is, the first white layer 3-1 is positioned on the black layer 4 side, and the second white layer 3-2 is positioned on the outer layer 5 side. Here, the first white layer 3-1 is a fully aromatic aliphatic polyester layer. The composition of the resin component in the second white layer 3-2 is not particularly limited, and for example, the same composition as that of the white layer 3 described in the previously described embodiment can be adopted.

[0055] The thickness of the fully aromatic aliphatic polyester layer is, for example, 1 to 15 μm, preferably 5 to 10 μm.

[0056] (Other) Next, other features of the biodegradable mulch film 1 according to this embodiment and its modified form will be described.

[0057] The overall thickness of the biodegradable mulch film 1 is, for example, 10 to 30 μm, preferably 15 to 20 μm.

[0058] The biodegradable mulch film 1 of this embodiment has high tear strength. For example, the tear strength of the biodegradable mulch film 1 is 0.7 N or higher. In a preferred embodiment, the tear strength is 1.0 N or higher. The tear strength of the biodegradable mulch film 1 is measured by the method described in the examples below.

[0059] The biodegradable mulch film 1 has high puncture strength. For example, the puncture strength of the biodegradable mulch film 1 is 0.7 N or higher. In a preferred embodiment, the puncture strength is 0.8 N or higher. The puncture strength of the biodegradable mulch film 1 is measured by the method described in the examples below.

[0060] The biodegradable mulch film 1 also exhibits excellent puncture indentation depth. For example, the puncture indentation depth of the biodegradable mulch film 1 is 2.5 mm or more. In a preferred embodiment, the puncture indentation depth is 3.0 mm or more. The puncture indentation depth of the biodegradable mulch film 1 is measured by the method described in the examples below.

[0061] As previously described, plant-derived resins can be used as part of the resin contained in the biodegradable mulch film 1. For example, the biodegradable mulch film 1 has a biomass content of 25% by weight or more. Preferably, the biomass content is 30% by weight or more. Such a biomass content can be achieved, for example, by using plant-derived PBS as the aliphatic polyester and plant-derived PBST as the aromatic aliphatic polyester.

[0062] The method for producing the biodegradable multifilm 1 is not particularly limited. For example, the biodegradable multifilm 1 having a multilayer structure can be produced by co-extrusion. For example, the inflation method can be used as the extrusion molding method.

[0063] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0064] (Example 1) Compositions for the white layer, black layer, outer layer, and inner layer were prepared. The prepared compositions were molded using co-extrusion (inflation method) to obtain the biodegradable mulch film according to Example 1. Table 1 shows the composition of each layer. In Table 1, the numbers in parentheses for aliphatic polyester and aromatic aliphatic polyester indicate the resin content within each layer. The unit of content is mass %. Bio-PBS (plant-derived PBS) was used as the aliphatic polyester. A mixture of Bio-PBST (plant-derived PBST) and PBAT in a mass ratio of 9:1 was used as the aromatic aliphatic polyester. Titanium dioxide was used as the white pigment. Calcium carbonate was used as the dispersion accelerator. A mixture of lubricants, antiblocking agents, and weather-resistant agents was used as other additives. The same applies to Example 2 and Comparative Example 1 below. In Example 1, the aliphatic polyester content in the entire colored layer group was 18% by mass, based on the resin.

[0065] (Example 2) A first white layer composition and a second white layer composition were prepared as white layer compositions, and the other compositions were prepared in the same manner as in Example 1. The prepared compositions were molded using co-extrusion (inflation method) to obtain a biodegradable mulch film according to Example 2. Table 1 shows the composition of each layer. The first white layer is a layer in which the resin component is aromatic aliphatic polyester, and is a fully aromatic aliphatic polyester layer. In Example 2, the aliphatic polyester content in the entire group of colored layers was 13% by mass on a resin basis.

[0066] In this embodiment, both Bio-PBST and PBAT had the structure shown by formula (B) described above, and the molar ratio of the constituent units (n1:n2) was in the range of 1.0:1.0 to 1.3:1.0.

[0067] Furthermore, the biomass content of the biodegradable mulch films in Example 1 and Example 2 was 25.7% by weight or more in both cases.

[0068] (Comparative Example 1) The content of aliphatic polyester and aromatic aliphatic polyester in the colored layer group was changed from that of Example 1. In other respects, the biodegradable mulch film according to Comparative Example 1 was obtained in the same manner as in Example 1. Table 1 shows the composition of each layer. In Comparative Example 1, the total aliphatic polyester content in the colored layer group exceeded 30% by mass on a resin basis.

[0069]

[0070] (Comparative Example 2) As Comparative Example 2, a biodegradable mulch film (thickness 20 μm) relating to commercially available product A was prepared. Commercial product A had a white layer and a black layer, but did not have an outer layer or an inner layer. The resin components contained in the white layer and the black layer were a mixture of PBAT (aromatic aliphatic polyester) and PLA (aliphatic polyester), and the content of the resin components relative to the total mass of the film was 74% by mass. Of the resin components, the content of PLA, which is an aliphatic polyester, was 10% by mass on a resin basis. In addition, inorganic substances including titanium dioxide as a white pigment were contained at a content of 26% by mass relative to the total mass of the film.

[0071] <Evaluation Method> For Examples 1 and 2 and Comparative Examples 1 and 2, tear strength, puncture strength, and puncture indentation depth were measured using the following method to evaluate the susceptibility of each film to tearing.

[0072] <Tear Strength> Using an Autograph (manufactured by Shimadzu Corporation), the tear strength in the MD direction of each sample was measured according to the following procedure. The film was cut into a rectangle with a long side (MD direction) of 150 mm and a short side (TD direction) of 40 mm, and a 75 mm notch was made in the MD direction at the center of one of the short sides. Next, both long sides were wrapped with reinforcing tape up to 3.5 mm from the end to prepare the sample. Then, using the Autograph, the distance between the chucks was set to 80 mm, the tapered portion of the sample was clamped between the upper and lower chucking fixtures, and one of the chuck fixtures was moved at a speed of 200 mm / min to measure the maximum stress (tear strength) required for the film to break. The ease with which each film would tear was evaluated from the tear strength obtained from the above measurement. Note that a higher tear strength indicates that the film is less likely to tear.

[0073] <Puncture Strength and Puncture Indentation> Using a weather resistance tester (Atlas Corporation, Ci4000), each sample was subjected to a puncture test of 110 W / m². ２ The samples were irradiated with light at 40°C for 120 hours. Then, using an Autograph (manufactured by Shimadzu Corporation), the puncture strength and puncture indentation depth of each sample were measured according to the following procedure. A rod-shaped puncture test fixture (a semi-circular needle with a diameter of 1.0 mm and a tip radius of 0.5 mm) was attached to the tip of the load cell of the puncture test machine, and the sample was then fixed to a fixing fixture. The puncture test fixture was then pressed into the sample at a puncture speed of 50 mm / min, and the maximum stress (puncture strength) and indentation depth (puncture indentation depth) required for the film to break were measured. The susceptibility of each film to tearing was evaluated based on the strength and indentation depth obtained from the above measurements. Note that a higher puncture strength and puncture indentation depth indicate a lower likelihood of tearing.

[0074] (Evaluation Results) Table 2 shows the measurement results for tear strength, puncture strength, and puncture indentation depth for Examples 1 and 2 and Comparative Examples 1 and 2.

[0075]

[0076] (Comparison of Example 1 and Comparative Example 2) Example 1 was equivalent to or better than Comparative Example 2 in terms of tear strength and puncture strength.

[0077] As previously mentioned, when aliphatic polyester is included in the resin layer, the film becomes more prone to tearing. The resin-based content of aliphatic polyester in the colored layer group of Example 1 (18% by mass) is higher than that of Comparative Example 2 (10% by mass). Therefore, based on the composition of the colored layer group, it can be expected that Example 1 will be more prone to tearing than Comparative Example 2. However, as stated above, the tear strength and puncture strength of Example 1 were equal to or higher than those of Comparative Example 2. From this, it can be concluded that Example 1, having an outer layer and inner layer containing aromatic aliphatic polyester, suppressed the occurrence of tearing despite containing a high content of aliphatic polyester.

[0078] (Comparison of Example 1 and Comparative Example 1) Example 1 was superior to Comparative Example 1 in tear strength, puncture strength, and puncture indentation depth. Specifically, as shown in Table 2, the tear strength of Example 1 was 0.7 N (= 1.1 - 0.4 N) greater than that of Comparative Example 1. Also, the puncture strength of Example 1 was 0.3 N (= 0.8 - 0.5 N) greater than that of Comparative Example 1. Furthermore, the puncture indentation depth of Example 1 was 1.4 mm (= 3.2 - 1.8 mm) greater than that of Comparative Example 1. From this, it can be understood that Example 1 is less prone to tearing than Comparative Example 1. In other words, if the aliphatic polyester content in the colored layer group is 30% by mass or less based on the resin, it can be said that the occurrence of tearing in the film can be suppressed.

[0079] (Comparison of Example 1 and Example 2) Comparing the measurement results of Example 1 and Example 2, Example 2 was superior in tear strength, puncture strength, and puncture indentation depth. Specifically, as shown in Table 2, the tear strength of Example 2 was 0.4 N (= 1.5-1.1 N) greater than that of Example 1. Also, the puncture strength of Example 2 was 0.1 N (= 0.9-0.8 N) greater than that of Example 1. Furthermore, the puncture indentation depth of Example 2 was 0.1 mm (= 3.3-3.2 mm) greater than that of Example 1. From this, it can be understood that Example 2 is less prone to tearing than Example 1. In other words, by providing a layer in the colored layer group whose resin component consists only of aromatic aliphatic polyester, the occurrence of tearing in the film can be suppressed more reliably.

[0080] [Note] The main embodiments and their effects included in the present invention are summarized below as a note.

[0081] (Note 1) A biodegradable mulch film comprising a group of colored layers 2 containing aliphatic polyester and a colorant, and a tear-resistant layer containing aromatic aliphatic polyester, wherein the group of colored layers 2 includes a white layer 3 containing a white pigment as a colorant and a black layer 4 containing a black pigment as a colorant, and the aliphatic polyester content in the group of colored layers 2 is 10% by mass or more and 30% by mass or less, based on the resin.

[0082] According to the above configuration, it is possible to suppress the occurrence of tearing in the film while still containing aliphatic polyester.

[0083] (Note 2) A biodegradable mulch film as described in Note 1, comprising an outer layer 5 and an inner layer 6 arranged to sandwich a group of colored layers 2, wherein the outer layer 5 and the inner layer 6 are tear-resistant layers.

[0084] According to the above configuration, it is possible to suppress the occurrence of tearing in the film while still containing aliphatic polyester.

[0085] (Note 3) A biodegradable mulch film as described in Note 1 or 2, wherein the aliphatic polyester contained in the colored layer group 2 is PBS (polybutylene succinate).

[0086] According to the above configuration, the biodegradability, moldability, mechanical properties, and short-term weather resistance of the film can be improved.

[0087] (Note 4) A biodegradable mulch film according to any one of Notes 1 to 3, wherein the colored layer group 2 includes a fully aromatic aliphatic polyester layer in which the resin component is an aromatic aliphatic polyester.

[0088] According to the above configuration, it is possible to more reliably suppress the occurrence of film tearing while still containing aliphatic polyester.

[0089] (Note 5) A biodegradable mulch film according to any one of Notes 1 to 4, wherein the white layer 3 comprises a first white layer 3-1 and a second white layer 3-2, the first white layer 3-1 is positioned between the black layer 4 and the second white layer 3-2, and the fully aromatic aliphatic polyester layer is the first white layer 3-1.

[0090] According to the above configuration, it is possible to more reliably suppress the occurrence of film tearing while still containing aliphatic polyester.

[0091] (Note 6) A biodegradable mulch film as described in any one of Notes 1 to 5, wherein the tear strength is 0.7 N or more.

[0092] (Note 7) A biodegradable mulch film as described in any one of Notes 1 to 6, wherein the biomass content is 25% by weight or more.

[0093] 1: Biodegradable mulch film, 2: Colored layer group, 3: White layer, 3-1: First white layer, 3-2: Second white layer, 4: Black layer, 5: Outer layer, 6: Inner layer

Claims

1. A biodegradable mulch film comprising: a group of colored layers containing aliphatic polyester and a colorant; and a tear-resistant layer containing aromatic aliphatic polyester, wherein the group of colored layers comprises: a white layer containing a white pigment as the colorant; and a black layer containing a black pigment as the colorant, and the aliphatic polyester content in the group of colored layers is 10% by mass or more and 30% by mass or less, based on the resin.

2. A biodegradable mulch film according to claim 1, comprising an outer layer and an inner layer arranged so as to sandwich the colored layer group, wherein the outer layer and the inner layer are the tear-resistant layers.

3. A biodegradable mulch film according to claim 1 or 2, wherein the aliphatic polyester included in the colored layer group is PBS (polybutylene succinate).

4. A biodegradable mulch film according to claim 1 or 2, wherein the colored layer group includes a fully aromatic aliphatic polyester layer in which the resin component is an aromatic aliphatic polyester.

5. A biodegradable mulch film according to claim 4, wherein the white layer comprises a first white layer and a second white layer, the first white layer is disposed between the black layer and the second white layer, and the fully aromatic aliphatic polyester layer is the first white layer.

6. A biodegradable mulch film according to claim 1 or 2, wherein the tear strength is 0.7 N or more.

7. A biodegradable mulch film according to claim 1 or 2, wherein the biomass content is 25% by weight or more.

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