JP2004314364A - Agricultural film with excellent weather resistance - Google Patents

Abstract

[PROBLEMS] To provide an agricultural PO film that can be suitably used even in a severe use environment represented by fruit tree cultivation on a slope such as a hill.
A low-density polyethylene containing at least one or more hindered amine compounds, having a density of 0.90 to 0.93 g / cm ³ and an MFR of 0.5 to 4.0 g / 10 minutes (190 ° C.) Ethylene-vinyl acetate copolymer having a vinyl acetate content of 3 to 15% by weight and an MFR of 0.5 to 4.0 g / 10 min (190 ° C.) on both sides of the intermediate layer having a thickness of 0.02 mm or more. An agricultural film having a total thickness of 0.03 to 0.15 mm, in which layers each having a thickness of 0.005 mm or more are laminated.
[Selection diagram] None

Description

【００３４】
実施例１は全項目に渡り良好な結果が得られたのに対し、比較例１は引っ張り破断強度が不足し、比較例２は引き裂き強度が不足する。また、比較例１及び２は共に耐候性試験において短時間で著しい強度低下を示した。
【００３５】
（実施例２、比較例３〜５）
表２に示す構成を有するフィルムをインフレーション成形法で三層共押出成形しフィルムを得た。得られたフィルムについて、後述の評価を行い、結果を表２に示した。
【００３６】
【表２】

【００３７】
実施例２は良好な結果が得られたのに対し、比較例３は引き裂き強度、耐光性が、比較例４は耐光性が、比較例５は引き裂き強度、耐光性が悪かった。
【００３８】
（実施例３、比較例６、７）
表３に示す構成を有するフィルムをインフレーション成形法で三層共押出成形しフィルムを得た、尚、比較例６は特許文献１に、比較例７は特許文献３にそれぞれ基づいて試作した。
実施例３、比較例６、および比較例７として作製したフィルムを山形県置賜地方の丘陵地に設営されているブドウ栽培施設に展張し、比較評価を行った。フィルムは略南向きの丘陵斜面へ約５０ｍの長さに展張され、上端と下端の標高差は約２５ｍであった。４月中旬に展張を行い、その後ブドウの生育に応じて適宜石灰硫黄合剤の散布が行われた。評価は、展張作業の容易性、５ヶ月後の破損状況により行い、結果を表３に示す。
【００３９】
【表３】

【００４０】
実施例３のフィルムは、展張時は問題もなく、５ヶ月後においても当初の状態を維持しており、耐候劣化による破損も強風による破損も見られず、また、ブドウの生育も良好であった。これに対し、比較例６および比較例７のフィルムは、展張時に問題を生じ、５ヶ月後においても破損が生じ、ブドウの実割れや落下等の障害が発生した。
【００４１】
〔評価方法〕
（破断点強度）
上記方法により得られた農業用フィルムの破断点強度をストログラフ（東洋精機製作所社製）によりＪＩＳ Ｋ−６７８１に準拠して測定した。
（引裂強度（エルメンドルフ法））
上記方法により得られた農業用フィルムの引裂強度をエルメンドルフ引裂強度測定機（東洋精機製作所社製）によりＪＩＳ Ｋ−７１２８に準拠して測定した。
（透明性（ヘーズ））
上記樹脂組成物より得られた農業用フィルム（作製直後）のヘーズ値を、ヘーズ測定機（日本電色工業社製：ＮＤＨ２０００）により測定した。
（耐候性（促進試験法））
耐候性の促進評価は、図１に示す試験装置を作製し、以下の条件にて耐候劣化試験を行い、破断に至るまでの期間を求めた。
先ず、フィルム試験片を石灰硫黄合剤希釈液（宮内硫黄合剤社製：１０倍水道水希釈）に２４時間浸漬し、その後表面をふき取らずに試験装置に図１に示した如く設置する。図１中１２の金属パイプには８０℃の温水を流量 ５リットル／分で流し続け、フィルムを部分的に加温状態に保持した。また、フィルムの一端は、図１中１３に示した分銅にて０．０２Ｎ／ｃｍの張力を与えた。さらに、上空から図１中１４に示す紫外線ランプを用いて５０Ｗ／ｍ^２の紫外線を照射した。
【００４２】
【図面の簡単な説明】
【図１】：フィルムの耐候性試験方法を示す模式図。
【符号の説明】
１・・・耐候性促進試験装置
１１・・・フィルム試験片
１２・・・金属製パイプ
１３・・・分銅
１４・・・紫外線ランプ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an agricultural film used for facility cultivation of agricultural products. More specifically, the present invention relates to an agricultural film that is covered and spread on the outer surface of a facility formed of metal pipes and the like and is used for purposes such as heat retention, rain protection, and wind protection. More specifically, the present invention relates to an agricultural film suitably used for institutional cultivation on an inclined surface of hills represented by fruit tree cultivation.
[0002]
[Prior art]
Conventionally, polyvinyl chloride film (hereinafter abbreviated as "agricultural PVC film"), polyolefin-based film (hereinafter abbreviated as "agricultural PO film"), and the like have been commonly used as plastic films spread at agricultural crop cultivation facilities. Have been. Because these films are always used outdoors, they can be caused by ultraviolet rays contained in sunlight, heat received from facility components heated by sunlight, fertilizers and pesticides used in facilities, and acid rain. Exposed to deteriorating factors. On the other hand, due to demands for facilitating the spreading operation, reducing the amount of waste after use, and reducing costs related to facilities, the development of the film in the direction of thinning has been promoted.
[0003]
Agricultural PVC films, which have been widely used in the past, are excellent in heat retention, weather resistance, transparency, and workability. On the other hand, there is a concern that toxic gas may be generated during incineration disposal after use. Is decreasing. Recently, the use of agricultural PO films as a film replacing agricultural PVC films has been rapidly increasing. Agricultural PO films have many advantages over agricultural PVC films, such as light weight, price, processability, mechanical strength, and ease of disposal.
[0004]
However, PO films are more vulnerable to the above-mentioned deterioration factors in outdoor use than PVC films, and various studies have been conducted to enable long-term use and use in areas where use conditions are severe. It has been done. That is, as a method for improving the resistance of the polyolefin-based film to the above-mentioned deterioration factors (hereinafter referred to as weather resistance), for example, a method using a hindered amine-based compound as an additive (see Patent Document 1) is disclosed. The hindered amine compound in the film tends to disappear in a short period of time under the condition involving water. As a means for allowing the hindered amine-based compound to be present in the film for a long period of time, a method of simultaneously adding a fine inorganic powder having a polarity is disclosed (see Patent Document 2). It has the drawback that its properties are remarkably reduced and it is no longer suitable for use as an agricultural coating film.
[0005]
Furthermore, agricultural films in which a polyolefin resin having a low vinyl acetate content is laminated on both sides of a center layer in which additives such as a hindered amine compound and inorganic fine powder are added to a polyolefin resin having a high vinyl acetate content. It is disclosed (see Patent Document 3).
[0006]
However, conventional agricultural PO films have been mainly used in cultivation facilities (generally referred to as "houses") installed on level ground, and the cultivated crops are basically vegetables and flowers. Therefore, a large tension is not continuously applied to the film, and a large amount of an acidic or basic drug is not sprayed, and the film is partially exposed to a large amount of ultraviolet light or high temperature. Few.
[0007]
On the other hand, fruit tree cultivation, particularly grape cultivation, is often performed on hills, that is, tension is concentrated on a high altitude portion on an inclined surface. In addition, the southward slope has a large amount of ultraviolet light per unit area, and the air under the film warmed by sunlight rises along the slope and the upper part has a high temperature. In addition, it is regularly practiced to spray a strongly basic lime-sulfur mixture with a large amount of dilution water. Under such severe conditions, conventional agricultural films are not sufficient, and there is a demand for agricultural films having better strength and weather resistance.
Furthermore, film stretching work on sloping surfaces in hills is extremely hard work, and the framework of the facility is often in a simple form. Therefore, a thinner agricultural film is required.
[0008]
[Patent Document 1]
JP-A-59-86645 [Patent Document 2]
JP-A-56-41254 [Patent Document 3]
Japanese Patent Application Laid-Open No. 7-313996
[Problems to be solved by the invention]
[0010]
An object of the present invention has been made in view of the above problems, and it is an object of the present invention to provide an agricultural PO film that can be suitably used even in a harsh use environment represented by fruit tree cultivation on a slope such as a hill. is there.
[0011]
[Means for Solving the Problems]
A thickness 0 made of low-density polyethylene containing at least one or more hindered amine-based compounds, having a density of 0.90 to 0.93 g / cm ³ and an MFR of 0.5 to 4.0 g / 10 minutes (190 ° C.) Thickness of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 3 to 15% by weight and an MFR of 0.5 to 4.0 g / 10 min (190 ° C.) on both sides of an intermediate layer of at least 0.02 mm A film for agricultural use, wherein layers having a thickness of 0.005 mm or more are laminated, and the total thickness is 0.03 to 0.15 mm.
[0012]
Hereinafter, the details will be described.
[0013]
The center layer of the present invention has a strength capable of withstanding the tension applied by being spread on the slope, and a role of preventing the film from being softened in a partially generated temperature rising state. It is necessary that the polyethylene resin used for the center layer is a low-density polyethylene, and among them, an ethylene-α-olefin copolymer, that is, a linear low-density polyethylene is more preferable. The density of the low-density polyethylene is 0.90 to 0.93 g / cm ³ , and the MFR is 0.5 to 4.0 g / 10 min (190 ° C.). The density in the present invention is a density measured in accordance with JIS K 7112 “Method for measuring density and specific gravity of plastics and non-foamed plastics”, and MFR is JIS K 7210 “Plastics-thermoplasticity”. Test Method for Plastics Melt Mass Flow Rate and Melt Volume Flow Rate "at 190 ° C.
[0014]
When the density of the low-density polyethylene resin is less than 0.90 g / cm ³ , the obtained agricultural film is insufficient in strength and unsuitable for stretching work, and has a low flexural modulus. A blocking phenomenon occurs during storage. On the other hand, when the density exceeds 0.94 g / cm ³ , the transparency of the obtained film is reduced, and there is a problem in use as an agricultural film. The preferred range of density is 0.91~0.93g / cm ^3.
[0015]
When the MFR of the low-density polyethylene resin is less than 0.5 g / 10 minutes (190 ° C.), the film forming property (productivity) of the agricultural film is impaired, and conversely, the MFR is 4.0 g / 10 minutes ( If it exceeds 190 ° C.), the mechanical strength of the obtained agricultural film becomes insufficient. When a co-extrusion method is used as the film forming means of the present invention, it is preferable that the MFR of the resin used for both outer layers described later and the MFR of the resin used for the center layer are made as close as possible.
[0016]
A hindered amine compound is added to the center layer as a weather resistance improver. As the hindered amine compound, any conventionally known compound can be used, and a single compound or a mixture of two or more compounds can be used. Specifically, dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine succinate polycondensate, tetrakis (2,2,6,6-tetramethyl- 4-piperidyl) -1,2,3,4-butanetetracarboxylate, poly {[6-[(1,1,3,3-tetramethylbutyl) amino] -1,3,5-triazine-2 4-diyl] [(2,2,6,6-tetramethyl-4-piperidyl) imino] hexamethylene [(2,2,6,6-tetramethyl-4-piperidyl) imino]} and the like.
[0017]
If necessary, a heat stabilizer, an antioxidant, an ultraviolet absorber and the like may be added to the center layer as long as the effects of the present invention are not impaired.
As the heat stabilizer, any conventionally known heat stabilizer can be used, and specific examples thereof include chelators such as metal salts of carboxylic acids, phenolic antioxidants, and organic phosphites.
As the antioxidant, any conventionally known antioxidant can be used, and usually, those having the effect of the heat stabilizer are often used. For example, metal salts of carboxylic acids, phenolic antioxidants, and organic phosphites And the like.
[0018]
As the above-mentioned ultraviolet absorber, any conventionally known one can be used. For example, benzophenone-based, benzotriazole-based, salicylate-based, cyanoacrylate-based and the like can be used alone or in combination of two or more. Specifically, as a benzophenone-based ultraviolet absorber, 2,4-dihydroxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, As a benzotriazole-based ultraviolet absorber such as 2,2'-hydroxy-4,4'-dimethoxybenzophenone and 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2- (2'-hydroxy-5'-tert- Butylphenyl) benzotriazole, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3′-tert-butyl-5-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-buty Phenyl) -5-chloro-benzotriazole, 2- (2'-hydroxy-3 ', 5'-di -tert- amylphenyl) -5-chloro-benzotriazole, and the like.
[0019]
The center layer preferably does not contain an antifogging agent.An antifogging agent has a property of migrating to the surface in a film, and when an antifogging agent is contained, a weathering agent is also added to the surface together with the antifogging agent. It shifts and the weather resistance, especially the long-term weather resistance, decreases. Therefore, when it is necessary to add an antifogging agent, the amount of the antifogging agent is preferably less than 20,000 ppm.
[0020]
Further, it is preferable that the center layer does not contain a heat retaining agent or the like which is inorganic fine particles. Inorganic fine particles typified by a heat insulating agent and the like have, for example, an action of trapping an acid, a basic substance, and the like contained in a drug, and as a result, promote deterioration of a film. Therefore, when it is necessary to provide heat retention, the amount of the heat retention agent is preferably less than 7% by weight.
[0021]
The thickness of the center layer needs to be 0.02 mm or more. When the thickness of the center layer is less than 0.02 mm, it is difficult to secure the above-described strength and heat resistance. The upper limit of the thickness of the central layer is not particularly limited, and is appropriately determined within a range not departing from the thickness of the entire film.
[0022]
The surface layer plays a role in preventing generation of fine cracks generated on the film surface due to ultraviolet rays, moisture, and the like. Acids and basic substances such as lime-sulfur mixture sprinkled as pesticides penetrate into the cracks formed on the film surface together with the moisture, and remarkably accelerate the deterioration of the physical properties of the film. The vinyl acetate content of the ethylene-vinyl acetate copolymer used for the surface layer is preferably 3 to 15% by weight, and the MFR is preferably 0.5 to 4.0 g / 10 minutes (190 ° C.).
[0023]
When the vinyl acetate content of the ethylene-vinyl acetate copolymer is less than 3% by weight, the flexibility of the surface becomes insufficient and the function of preventing the occurrence of fine cracks becomes insufficient. Conversely, if the vinyl acetate content exceeds 15% by weight, a fusing phenomenon occurs during storage, which is not preferable. A more preferred vinyl acetate content is 5 to 10% by weight.
[0024]
When the MFR of the ethylene-vinyl acetate copolymer is less than 0.5 g / 10 min (190 ° C.), the film forming property (productivity) of the agricultural film is impaired, and conversely, the MFR is 4.0 g / 10. When the temperature exceeds 190 ° C. (190 ° C.), the rupture strength is reduced, and the function of preventing the generation of fine cracks becomes insufficient. More preferably, it is in the range of 0.8 to 2.0 g / 10 minutes (190 ° C.).
[0025]
In order to allow the condensed water droplets to flow onto the surface layer composed of the ethylene-vinyl acetate copolymer layer, an antifogging agent may be kneaded as necessary, or an antifogging film may be formed on the surface. good.
As the antifogging agent, any conventionally known one can be used, and polyhydric alcohol fatty acid esters are preferably used. Specifically, polyhydric alcohol-saturated fatty acid esters such as glycerin stearic acid ester, diglycerin stearic acid ester, polyglycerin stearic acid ester, and sorbitol stearic acid ester; And a polyhydric alcohol-unsaturated fatty acid ester.
Examples of the antifogging film formed on the surface of the laminated film include a coating film of an inorganic oxide sol represented by, for example, colloidal silica and colloidal alumina, and as an application thereof, an inorganic oxide sol and an organic compound (interfacial activity). Coating films such as agents and resins), coating films of liquids mainly containing surfactants, films mainly containing hydrophilic resins (for example, polyvinyl alcohol, polyethylene oxide, polysaccharides, polyacrylic acid, etc.). ) And the like.
[0026]
Other additives and the like may be added to the surface layer composed of the ethylene-vinyl acetate copolymer layer as long as the effects of the present invention are not impaired. However, it is preferable to avoid adding inorganic fine particles such as a heat insulator and an anti-blocking agent. As described above, the inorganic fine particles have an effect of inhibiting transparency and capturing an acid, a basic substance, and the like contained in a drug to be used, and as a result, promote deterioration of the film. It is preferable to use organic fine particles when taking measures of imparting heat retention and blocking, and to use as little as possible when using inorganic fine particles.
[0027]
The thickness of the above-mentioned surface layer needs to be 0.005 mm or more. When the thickness of the surface layer is less than 0.005 mm, the function of preventing the above minute cracks becomes insufficient. The upper limit of the thickness of the surface layer is not particularly limited, and is appropriately determined within a range that does not deviate from the thickness of the entire film.
[0028]
The agricultural PO film of the present invention has a configuration in which surface layers are laminated on both sides of a center layer, and the entire thickness is 0.03 to 0.15 mm, preferably 0.05 to 0.1 mm. Range. When the thickness is less than 0.03 mm, the absolute strength of the film is insufficient, and the film is easily broken by a mechanical force such as a strong wind. Further, the strength is significantly reduced due to the progress of weather resistance deterioration, which is not preferable. On the other hand, when the thickness exceeds 0.15 mm, the weight per unit area of the film becomes excessively large, and it becomes difficult to perform the stretching operation on a hill. Further, the cost of the film per unit area increases, which is not preferable from the economical viewpoint.
[0029]
The method for producing the agricultural PO film of the present invention is not particularly limited, and any conventionally known method may be employed. Examples thereof include a multilayer inflation method, a multilayer T-die method, a multilayer lamination method, and a calendar method. Can be
[0030]
The use of the agricultural PO film of the present invention is not only suitable for orchard cultivation in hills as described above, but also in fields where light weight and high strength are required, such as adhesion of agricultural chemicals and fertilizers to the film is inevitable. It can also be suitably used in fields such as For example, curtains used inside agricultural houses and rain shelters at composting plants correspond to these.
[0031]
Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
[0032]
【Example】
(Example 1, Comparative Examples 1 and 2)
A film having the configuration shown in Table 1 was co-extruded in three layers by an inflation molding method to obtain an agricultural film. The overall thickness of each film was the same as shown in the table. The obtained film was evaluated as described below, and the results are shown in Table 1.
The MFR shown in the table indicates a melt mass flow rate, and is a value measured at a temperature of 190 ° C. and a load of 21.18 N according to JIS K7210.
[0033]
[Table 1]

[0034]
In Example 1, good results were obtained for all items, whereas Comparative Example 1 was insufficient in tensile breaking strength, and Comparative Example 2 was insufficient in tear strength. Further, both Comparative Examples 1 and 2 showed a remarkable decrease in strength in a short time in the weather resistance test.
[0035]
(Example 2, Comparative Examples 3 to 5)
A film having the structure shown in Table 2 was co-extruded in three layers by an inflation molding method to obtain a film. The obtained film was evaluated as described below, and the results are shown in Table 2.
[0036]
[Table 2]

[0037]
In Example 2, good results were obtained, whereas Comparative Example 3 was poor in tear strength and light resistance, Comparative Example 4 was poor in light resistance, and Comparative Example 5 was poor in tear strength and light resistance.
[0038]
(Example 3, Comparative Examples 6, 7)
A film having the structure shown in Table 3 was co-extruded in three layers by an inflation molding method to obtain a film. Comparative Examples 6 and 7 were prototyped based on Patent Document 1 and Patent Document 3, respectively.
The films produced in Example 3, Comparative Example 6, and Comparative Example 7 were spread on a grape cultivation facility established on a hill in the Okita area of Yamagata Prefecture, and comparative evaluation was performed. The film was stretched approximately 50 m long on a hill slope almost facing south, and the difference in elevation between the top and bottom was about 25 m. Spreading was carried out in mid-April, and thereafter a lime-sulfur mixture was sprayed appropriately according to the growth of the grapes. The evaluation was performed based on the ease of the spreading operation and the damage status after 5 months, and the results are shown in Table 3.
[0039]
[Table 3]

[0040]
The film of Example 3 had no problem at the time of stretching, and maintained its initial state even after 5 months. No damage due to weather resistance or damage due to strong wind was observed, and the growth of grapes was good. Was. On the other hand, the films of Comparative Examples 6 and 7 had a problem at the time of stretching, and even after 5 months, they were damaged, and failures such as actual cracking of the grape and dropping occurred.
[0041]
〔Evaluation method〕
(Strength at break)
The breaking point strength of the agricultural film obtained by the above method was measured by a strograph (manufactured by Toyo Seiki Seisaku-sho, Ltd.) in accordance with JIS K-6781.
(Tear strength (Elmendorf method))
The tear strength of the agricultural film obtained by the above method was measured by an Elmendorf tear strength measuring machine (manufactured by Toyo Seiki Seisaku-sho, Ltd.) in accordance with JIS K-7128.
(Transparency (haze))
The haze value of the agricultural film (immediately after production) obtained from the resin composition was measured with a haze measuring device (NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd.).
(Weather resistance (accelerated test method))
For the evaluation of the promotion of weather resistance, a test apparatus shown in FIG. 1 was prepared, a weather resistance deterioration test was performed under the following conditions, and a period until breakage was obtained.
First, the film test piece is immersed in a lime sulfur mixture dilution liquid (manufactured by Miyauchi Sulfur Mixture: 10 times diluted with tap water) for 24 hours, and then placed in a test apparatus without wiping the surface as shown in FIG. . Hot water at 80 ° C. was continuously supplied to the metal pipes 12 in FIG. 1 at a flow rate of 5 liter / min to keep the film partially heated. One end of the film was given a tension of 0.02 N / cm by the weight shown in FIG. Further, ultraviolet light of 50 W / m ² was irradiated from above using an ultraviolet lamp 14 shown in FIG.
[0042]
[Brief description of the drawings]
FIG. 1 is a schematic view showing a weather resistance test method of a film.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Weathering acceleration test apparatus 11 ... Film test piece 12 ... Metal pipe 13 ... Weight 14 ... UV lamp

Claims (1)

A thickness 0 made of low-density polyethylene containing at least one or more hindered amine compounds, having a density of 0.90 to 0.93 g / cm ³ and an MFR of 0.5 to 4.0 g / 10 min (190 ° C.) Thickness of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 3 to 15% by weight and an MFR of 0.5 to 4.0 g / 10 min (190 ° C.) on both sides of an intermediate layer having a length of 0.02 mm or more. A film for agricultural use, wherein layers having a thickness of 0.005 mm or more are laminated, and the total thickness is 0.03 to 0.15 mm.

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