Agricultural film and method for producing agricultural film

Abstract

To provide an agricultural film that makes use of the advantages of polyolefin-based agricultural films, such as long usable life and environmental friendliness owing to the absence of chlorine, while also achieving performance equivalent or superior to those of polyvinyl chloride agricultural films, such as flexibility, and resistance to abrasion and tearing.SOLUTION: An agricultural film comprises: a first layer; a second layer laminated adjacent to the first layer; and a third layer laminated adjacent to the side of the second layer opposite the first layer, wherein the first layer comprises a metallocene plastomer having a melting point of 97°C or less, a slip agent, and an anti-blocking agent, and the content of the metallocene plastomer is 90 mass% or more based on the total amount of the first layer, wherein the second layer contains an ethylene-vinyl acetate copolymer and a heat-retaining agent, and wherein the agricultural film is used such that overlapping areas of the first layer are peeled apart during deployment.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an agricultural film and a method for manufacturing the agricultural film, and more particularly to an agricultural film that is used by being stretched in a tunnel shape. [Background technology]

[0002] Tunnel-shaped agricultural films are often used in crop cultivation for the purposes of increasing the growing temperature of crops and protecting the growing crops from snow, etc. Such agricultural films are required to be highly flexible, have high heat retention, be resistant to abrasion and tear caused by fixing bands and wind, etc. (high abrasion and tear resistance), and be easy to unfold when installed (high peelability between overlapping layers), etc.

[0003] Traditionally, polyvinyl chloride has been widely used for tunnel-shaped agricultural films used for each row of crop cultivation (see Patent Document 1, etc.). Polyvinyl chloride agricultural films are soft and flexible, and are not easily torn even when rubbed. However, the period during which they can be stretched (the period during which they can be used) is short, ranging from about six months to about two years at most, depending on the situation. With the rising cost of disposing of waste polyvinyl chloride film and the issue of global warming being discussed, a material to replace polyvinyl chloride was required.

[0004] As an alternative to polyvinyl chloride for agricultural film materials, polyolefin-based films such as polyolefin and olefin-vinyl acetate copolymers have been attracting attention (see Patent Document 1, etc.). These polyolefin-based films have a long spreadable period (usable period) of generally more than two years, and are excellent in durability and weather resistance. However, compared to conventional polyvinyl chloride agricultural films, they have issues such as inferior flexibility and heat retention, and are also somewhat less resistant to tearing when rubbed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-219004 Summary of the Invention [Problem to be solved by the invention]

[0006] The main object of the present invention is to provide an agricultural film that has flexibility, abrasion resistance, tear resistance, etc. equivalent to or greater than those of polyvinyl chloride agricultural films, while taking advantage of the advantages of polyolefin-based agricultural films, such as a long usable period and environmental friendliness because they do not contain chlorine. [Means for solving the problem]

[0007] In order to solve such problems, the inventors have made extensive efforts to develop an olefin-based (polyolefin, polyolefin-vinyl acetate copolymer, etc.) agricultural film that is equal to or better than polyvinyl chloride agricultural films. That is, the agricultural film of the present invention comprises a first layer, a second layer laminated adjacent to the first layer, and a third layer laminated adjacent to the second layer on the opposite side to the first layer, wherein the first layer contains a metallocene-based plastomer having a melting point of 97°C or less, a slip agent, and an antiblocking agent, the content of the metallocene-based plastomer being 90 mass% or more relative to the total amount of the first layer, the second layer contains an ethylene-vinyl acetate copolymer and a heat-retaining agent, and is used so that the overlapping first layers are peeled off when the film is unfolded.

[0008] The density of the first layer is 0.94 g / cm 3 It is preferable that:

[0009] The slip agent of the first layer may be one or more compounds selected from the group consisting of silicon-acrylic copolymer, erucamide, and oleamide, and the antiblocking agent of the first layer may be one or more compounds selected from the group consisting of aluminum hydroxide, synthetic silica, and calcium carbonate having a particle size of 4 μm to 8 μm.

[0010] The heat retaining agent of the second layer is hydrotalcite, and the content of the heat retaining agent in the second layer is preferably 8% by mass or more and 12% by mass or less with respect to the total amount of the second layer.

[0011] The ratio of the thickness of the first layer to the thickness of the second layer to the thickness of the third layer is preferably 1:2.5 to 6.0:1.

[0012] The method for producing an agricultural film of the present invention includes an inflation step using a three-layer inflation molding device, in which a second layer is sandwiched between a first layer and a third layer, and the first layer is extruded so as to become an inner layer of a tubular film; and a cutting step of at least one end of the tubular film. the first layer comprises a metallocene-based plastomer having a melting point of 97°C or less, a slip agent, and an antiblocking agent, the metallocene-based plastomer being 90% by mass or more of the total amount of the first layer, and the second layer comprises an ethylene-vinyl acetate copolymer and a heat retaining agent. Effect of the Invention

[0013] The present invention makes it possible to provide an agricultural film that has the same or greater flexibility, abrasion resistance, tear resistance, etc. as polyvinyl chloride agricultural films, while taking advantage of the advantages of polyolefin-based agricultural films, such as a long usable period and environmental friendliness because they do not contain chlorine. [Brief description of the drawings]

[0014] [Figure 1] An example of a method for producing the agricultural film of the present invention will be outlined below. [Diagram 2] 1 shows an example of a cross-sectional view of the agricultural film of the present invention. [Diagram 3] 1 is a photograph of an example of the agricultural film of the present invention. [Figure 4] 1 is a photograph of another example of the agricultural film of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The embodiments of the present invention will be specifically described below, but the present invention is not limited to these embodiments.

[0016] The agricultural film A of the present invention comprises a first layer 1 , a second layer 2 and a third layer 3 .

[0017] The agricultural film A is a covering material used in tunnels and greenhouses for the purpose of increasing the growing temperature of agricultural crops and protecting the growing crops from snow, etc. The agricultural film A of the present invention is particularly suitable for tunnel-shaped agricultural films that require frequent film spreading and frequent film turning over for crop status checks, ventilation, etc. The tunnel-shaped agricultural film A can cover tunnels with a width of 100 cm to 200 cm, a height of 50 cm to 100 cm, and a length of about 50 m to 100 m. That is, in order to cover a tunnel, it is desirable that the agricultural film A opened by cutting the end of the cylindrical film A0 along the cutting line L has a width in the range of 130 cm to 400 cm, preferably about 200 cm to 300 cm (see FIG. 1).

[0018] Figure 2 shows a cross-sectional view of agricultural film A. Note that, to facilitate understanding, the length and width of the drawing are on different scales, and the thickness direction is larger than the width direction. The first layer 1 is located on the outermost side of the agricultural film A, and is formed on the outermost side of the tunnel when it is wrapped in a tunnel shape. In the cylindrical film A0 shown in FIG. 1, the first layer 1 is formed on the innermost side, and the first layers 1 are in contact with each other. In many cases, the cylindrical film A0 is cut at a cutting line L at at least one end at the site where it is wrapped in a tunnel shape, and the first layers 1 that are in contact with each other are peeled off and spread out. The spreading work can be performed on a support frame for the tunnel, or can be performed by one person. After spreading, the agricultural film A is formed with the first layer 1 on the outside, and it can be wrapped in a tunnel shape using the support frame for the tunnel.

[0019] During storage and distribution, the first layer 1 becomes an inner layer of the tubular film A0, and the surfaces of the first layers 1 come into contact with each other and overlap. On the other hand, during use, at least one end of the tubular film A0 is cut along the cutting line L, the contact between the first layers 1 is peeled off, and the film is stretched, so that the first layer 1 is positioned on the outermost side of the agricultural film A. To perform this operation smoothly, the agricultural film A, and in particular the first layer 1, is required to have strength, resistance to abrasion and tear, as well as flexibility and peelability.

[0020] In order to have such properties, the first layer 1 contains, as a basic material, a plastomer having plasticity at about room temperature, and at least a slip agent and an antiblocking agent (AB agent).

[0021] The plastomer of the first layer 1 is a metallocene plastomer, and is a polyolefin film containing polyethylene, having a melting point of 97° C. or less, preferably 95° C. or less, and more preferably 93° C. or less. In contrast, many of the conventionally widely used linear low-density polyethylenes have a melting point of around 115° C. Metallocene plastomers having a melting point in the above range are more resistant to tearing due to abrasion against the support frame of a tunnel, etc., and can also have improved flexibility, compared to conventional linear low-density polyethylenes and the like. The density of the metallocene plastomer used in the first layer 1 is 0.94 g / cm 3 or less, preferably 0.93 g / cm 3 Less than or equal to 0.91 g / cm 3 is less than.

[0022] The content of the metallocene plastomer in the first layer 1 is 90% by mass or more, preferably 92% by mass or more, and more preferably 94% by mass or more, based on the total amount of the first layer 1. In addition to the metallocene plastomer, the first layer 1 may contain a polyolefin polymer (linear or branched) including polyethylene, but it is preferable not to do so.

[0023] The slip agent contained in the first layer 1 is an additive that can reduce friction between the film and the processing machine during film formation and between the materials of the film. Examples of slip agents include erucic acid amide, oleic acid amide, stearic acid amide, stearic acid, stearic acid monoglyceride, stearyl stearate, and silicone-acrylic copolymer. The first layer 1 may contain one of these slip agents, or two or more of them may be used in combination. Among them, erucic acid amide, oleic acid amide, and silicone-acrylic copolymer are more preferable.

[0024] The antiblocking agent contained in the first layer 1 is an additive that can reduce stickiness and adhesion between films. The antiblocking agent forms irregularities on the film surface using fine particles, thereby reducing contact between films. Examples of antiblocking agents include aluminum hydroxide, synthetic silica, calcium carbonate, synthetic zeolite, etc. The first layer 1 may contain one of these antiblocking agents, or two or more of them may be used in combination. The particle size of the antiblocking agent is preferably from 4 μm to 8 μm, and more preferably from 5 μm to 7 μm.

[0025] In addition, the first layer 1 may optionally contain various additives that are commonly used in films.

[0026] The second layer 2 is adjacent to the first layer 1 and the third layer 3, and is laminated so as to be sandwiched between the first layer 1 and the third layer 3 (see FIG. 2). The second layer 2 is disposed as an intermediate layer among the layers of the film both in the tubular film A0 during storage and distribution and in the agricultural film A during use (after being spread out).

[0027] The second layer 2 is required to have properties such as enhancing heat retention. For this reason, the second layer 2 contains an ethylene-vinyl acetate copolymer as a basic material and at least a heat retaining agent.

[0028] The ethylene-vinyl acetate copolymer of the second layer 2 has a vinyl acetate content of 4% by mass or more and 40% by mass or less, and preferably 10% by mass or more and 30% by mass or less, relative to the ethylene-vinyl acetate copolymer. Within this content range, the ethylene-vinyl acetate copolymer has the properties of a thermoplastic elastomer.

[0029] The content of the ethylene-vinyl acetate copolymer in the second layer 2 is 80% by mass or more, and preferably 85% by mass or more, based on the total amount of the second layer 2.

[0030] The heat retaining agent contained in the second layer 2 is preferably one having an infrared absorbing function, and an example of such a heat retaining agent is hydrotalcite, which is a Mg / Al-based layered compound. The content of the heat retaining agent in the second layer 2 is 8% by mass or more and 12% by mass or less, and more preferably 10% by mass or more and 12% by mass or less, relative to the total amount of the second layer 2. When the heat retaining agent is hydrotalcite, foaming occurs easily if the content exceeds 12% by mass relative to the second layer 2. Note that foaming affects the appearance, but slight foaming does not affect various physical properties.

[0031] In addition, various additives that are usually used in films may be optionally blended into the second layer 2. In particular, it is preferable to blend an anti-fogging agent, and examples of the anti-fogging agent include diglycerin-based compounds, and it is more preferable to blend the anti-fogging agent in an amount of 1.5% by mass to 2.5% by mass based on the total amount of the second layer 2.

[0032] The third layer 3 is laminated adjacent to the second layer 2 on the opposite side to the first layer 1 (see FIG. 2). The third layer 3 becomes the outer layer of the tubular film A0 during storage and distribution. On the other hand, during use, at least one end of the tubular film A0 is cut along the cutting line L, the first layers 1 are peeled off from each other, and the film is stretched, so that the third layer 3 becomes the innermost layer of the agricultural film A. In other words, the third layer 3 becomes the layer on the inside of the tunnel.

[0033] The third layer 3 can contain basic materials and additives that are generally used in tunnel-shaped agricultural films. For example, ethylene-vinyl acetate copolymer is used as the basic material, diglycerin-based compounds are used as anti-fogging agents, and other antioxidants are used. These agents may be added as masterbatches.

[0034] The thickness ratio of the first layer 1, the second layer 2, and the third layer 3 is preferably 1:2.5 to 6.0:1, more preferably 1:3.0 to 5.0:1, and even more preferably 1:5:1. By increasing the thickness ratio of the second layer 2, the heat retention and flexibility of the agricultural film A can be improved. Furthermore, the thickness of the first layer 1 and the third layer 3 is preferably 3 μm or more and 30 μm or less, and more preferably 5 μm or more and 15 μm or less. When the ratio of the thicknesses of the first layer 1, the second layer 2, and the third layer 3 is 1:5:1, the total thickness of the first layer 1, the second layer 2, and the third layer 3 is preferably 21 μm or more and 210 μm or less, and more preferably 35 μm or more and 105 μm or less.

[0035] The ethylene-vinyl acetate copolymer, which is the basic material exemplified by the second layer 2 and the third layer 3, is more flexible than low-density polyethylene and metallocene-based elastomers. However, the first layer 1 is required to have physical properties necessary for molding, including reducing friction during film molding, and is required to reduce stickiness because it is the inner layer in the tubular film A0 and the first layers 1 come into contact with each other. It is also required to have peelability and flexibility during expansion, and is required to have strength that does not break when rubbed against the tunnel support frame (see Figure 3, etc.). Since it is necessary to satisfy such requirements, it is difficult to use ethylene-vinyl acetate copolymer as the basic material of the first layer 1. Therefore, a metallocene-based plastomer that has the above-mentioned physical properties, is highly flexible, and has plasticity near room temperature is applied to the first layer 1.

[0036] The manufacturing method of the agricultural film A of the present invention includes an inflation step using a three-layer inflation molding device, in which a second layer is sandwiched between a first layer and a third layer and extruded so that the first layer becomes the inner layer of a tubular film A0, and a step of cutting at least one end of the tubular film A0. In the inflation process, inflation molding is carried out using a known method. Furthermore, the step of cutting at least one end of the tubular film A0 is mainly carried out at the site of use, and involves cutting along a cutting line L using a cutter or the like (see FIG. 1). The first layer 1 and the second layer 2 are as described above. EXAMPLES

[0037] An example of agricultural film A of the present invention is shown below. Samples 1-3 in Table 1 and sample 4 as a comparative example were blended, and using a three-layer inflation molding device (40 mmΦ three-layer extruder manufactured by Yoshii Iron Works, model number YEI-40, or equivalent), the second layer was sandwiched between the first and third layers, and the first layer was extruded to become the inner layer of the tubular film A0 to form a tubular film A0. One end of the cylindrical film A0 was cut to obtain agricultural film A as a sample.

[0038] The obtained samples were subjected to the following evaluation tests, and the evaluation results are also shown in Table 1.

[0039] (Appearance evaluation) The appearance of the sample was evaluated by visual inspection. The appearance of the sample was evaluated for the presence or absence of bubbles in the intermediate layer. In sample 3, some foaming was observed in the second layer 2. This foaming is thought to be due to the high content of heat retaining agent. Although foaming affects the appearance, it is evaluated that only a small amount of foaming does not affect the various physical properties.

[0040] (Evaluation of abrasion resistance) The abrasion resistance was evaluated by performing a Gakushin abrasion test 500 times on the obtained samples using a test device (Suga Testing Machine, Model FR-2), and visually checking the test pieces for tears and scratches after the test. If the abrasion resistance (resistance to abrasion) is low, the surface of the sample will be torn, and if the abrasion resistance is high, the scratches on the surface of the sample will be shallow and small. Cases that were equivalent to polyvinyl chloride agricultural film were marked with an ◎, those that were inferior to polyvinyl chloride agricultural film but had a particularly good surface condition were marked with a ○+, those in good surface condition were marked with an ○, those that were equivalent to the comparative example sample 4, which is the current product, were marked with a △, and those whose surface condition was inferior to the current product were marked with an ×. In samples 1-3, the evaluation results were all good or especially good, compared to the comparative example, sample 4, which is the current product.

[0041] (Evaluation of the coefficient of friction) The coefficient of friction between the first layers 1 was evaluated. Using a test device (manufactured by Tester Sangyo), one day after film formation, the sample was attached to a movable floor surface (plate) and weight so that the first layers 1 were in contact with each other, and the dynamic coefficient of friction was measured. The comparative example of sample 4 had a value of 0.366, whereas samples 1-3 had values ​​of 0.309-0.350, indicating that friction between the inner layers in the tubular film A0 was reduced.

[0042] (Evaluation of adhesion (peel strength)) The adhesion between the first layers 1 was evaluated. The film (sample) immediately after film formation was cut into a size of 10 cm x 10 cm, and the first layers 1 were stacked on top of each other and heated at 70°C x 10 kgf x 15 H. After cooling to room temperature, a Strograph (Toyo Seiki Co., Ltd., model number VGIF) was used to measure the peel force when the two sheets were peeled off at a speed of 100 mm / min. The peel strength of the comparative example, sample 4, was 9.7 gf / 10 cm, whereas samples 1-3 had peel strengths of 10.1 gf / 10 cm-13.4 gf / 10 cm, indicating that the peel strength between first layers 1 was improved compared to the comparative examples.

[0043] (Evaluation of heat retention) The heat retention of the obtained samples was evaluated. The evaluation was performed by transmission measurement using an FT-IR (Fourier transform spectrophotometer, JASCO Corporation, FT / IR-4000). Wave number: 400 cm -1 ~1250cm -1 The infrared blocking rate within this range was defined as the heat retention index and compared. The heat retention index of the comparative example, sample 4, was 55, whereas that of samples 1-3 was 67-69, indicating that the heat retention was improved compared to the comparative examples.

[0044] [Table 1]

[0045] The present invention may have the following configurations. [Section 1] An agricultural film, A first layer; a second layer laminated adjacent to the first layer; a third layer laminated adjacent to the second layer on a side opposite to the first layer; Equipped with the first layer includes a metallocene plastomer having a melting point of 97° C. or less, a slip agent, and an antiblocking agent, and the content of the metallocene plastomer is 90% by mass or more based on the total amount of the first layer; the second layer comprises an ethylene-vinyl acetate copolymer and a thermal insulating agent; The agricultural film is used in such a way that the overlapping portions of the first layers are peeled off when the film is stretched. [Section 2] The density of the first layer is 0.94 g / cm 3 Item 3. The agricultural film according to item 1, which is as follows: [Section 3] 3. The agricultural film according to item 1 or 2, wherein the slip agent of the first layer is one or more compounds selected from the group consisting of silicon-acrylic copolymer, erucic acid amide, and oleic acid amide, and the antiblocking agent of the first layer is one or more compounds selected from the group consisting of aluminum hydroxide, synthetic silica, and calcium carbonate having a particle size of 4 μm or more and 8 μm or less. [Section 4] 4. The agricultural film according to any one of items 1 to 3, wherein the heat retaining agent of the second layer is hydrotalcite, and the content of the heat retaining agent in the second layer is 8% by mass or more and 12% by mass or less with respect to the total amount of the second layer. [Section 5] 5. The agricultural film according to any one of items 1 to 4, wherein a ratio of thicknesses of the first layer, the second layer, and the third layer is 1:2.5 to 6.0:1. [Section 6] A method for producing an agricultural film, comprising the steps of: an inflation process using a three-layer inflation molding device, sandwiching the second layer between the first layer and the third layer, and extruding the first layer to form an inner layer of a tubular film; cutting at least one end of the tubular film; Including, the first layer includes a metallocene plastomer having a melting point of 97° C. or less, a slip agent, and an antiblocking agent, the metallocene plastomer being present in an amount of 90% by mass or more based on the total amount of the first layer; The second layer comprises an ethylene-vinyl acetate copolymer and a thermal insulation agent. [Explanation of symbols]

[0046] Agricultural film A0 Cylindrical film 1. First Layer 2. Second Layer 3. The third layer L cutting line

Claims

1. An agricultural film, A first layer; and a second layer laminated adjacent to the first layer; a third layer laminated adjacent to the second layer on a side opposite to the first layer; Equipped with the first layer includes a metallocene plastomer having a melting point of 97° C. or less, a slip agent, and an antiblocking agent, and the content of the metallocene plastomer is 90% by mass or more based on the total amount of the first layer; the second layer comprises an ethylene-vinyl acetate copolymer and a thermal insulating agent; The agricultural film is used in such a way that the overlapping portions of the first layers are peeled off when the film is stretched.

2. The density of the first layer is 0.94 g / cm 3 2. The agricultural film of claim 1, wherein:

3. 3. The agricultural film according to claim 1 or 2, wherein the slip agent of the first layer is one or more compounds selected from the group consisting of silicon-acrylic copolymer, erucic acid amide, and oleic acid amide, and the antiblocking agent of the first layer is one or more compounds selected from the group consisting of aluminum hydroxide, synthetic silica, and calcium carbonate, each having a particle size of 4 μm to 8 μm.

4. 2. The agricultural film according to claim 1, wherein the heat retaining agent of the second layer is hydrotalcite, and the heat retaining agent is present in an amount of 8% by mass to 12% by mass relative to the total amount of the second layer.

5. 2. The agricultural film according to claim 1, wherein a ratio of thicknesses of the first layer, the second layer, and the third layer is 1:2.5 to 6.0:

1.

6. A method for producing an agricultural film, comprising the steps of: an inflation process using a three-layer inflation molding device, sandwiching the second layer between the first layer and the third layer, and extruding the first layer to form an inner layer of a tubular film; cutting at least one end of the tubular film; Including, The first layer includes a metallocene plastomer having a melting point of 97° C. or less, a slip agent, and an antiblocking agent, and the metallocene plastomer is present in an amount of 90% by mass or more based on the total amount of the first layer; The second layer comprises an ethylene-vinyl acetate copolymer and a thermal insulation agent.

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