Anti-fog agent for agricultural films and agricultural films

Abstract

To provide an antifogging agent having no perfluoroalkyl group and capable of suppressing the generation of fog (particularly, continuously suppressing the generation of fog) in a greenhouse by being added to an agricultural film, and also to provide an agricultural film comprising the fog preventive agent added thereto.SOLUTION: An antifogging agent for an agricultural film comprises, as an active ingredient, polydimethylsiloxane modified with polyether at both ends and having an HLB value of 5.3 or more and less than 7 and a mass average molecular weight of 3,600 or more and less than 7,000. The modified polydimethylsiloxane has a structure represented by the following general formula (1) in which an ethyleneoxy group and a propyleneoxy group are added to both ends of polydimethylsiloxane. [In the formula, C2H4O represents an ethyleneoxy group; C3H6O represents a propyleneoxy group; a, b, m, and n indicate the average addition moles of the respective units; a and b are the same or different and represent an integer of 1 or more; and m and n represent integers of 1 or more].SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an anti-fog agent that suppresses the generation of fog in an agricultural greenhouse, and an agricultural film containing the anti-fog agent. [Background technology]

[0002] In recent years, agricultural crops have been widely cultivated under synthetic resin films, such as in greenhouses and tunnels. It is known that water vapor evaporating from the soil or crops can cause the film surface to become cloudy or water droplets to adhere to it, resulting in a decrease in the cultivability of crops due to insufficient sunlight and the occurrence of crop diseases due to the dropping of water droplets. Therefore, conventional synthetic resin films used in the cultivation of agricultural crops (hereinafter referred to as "agricultural films") have been anti-fog films in which the film surface has been made hydrophilic by adding nonionic surfactants or the like. When covered with such anti-fog films, fog is likely to form near the film on the inner surface of the greenhouse in the mornings and evenings from autumn to winter, when the temperature difference between the inside and outside of the greenhouse becomes large. This fog is believed to be the cause of pest infestation in crops, and therefore it is necessary to suppress the generation of fog in greenhouse cultivation. Currently, fluorochemical surfactants are used as anti-fog agents to suppress the generation of fog (Patent Document 1, Patent Document 2).

[0003] Fluorosurfactants are C n H 2n+1 It is a surfactant with a perfluoroalkyl group, in which all hydrogen atoms (H) in the alkyl group are replaced with fluorine atoms (F). It has been suggested that compounds with perfluoroalkyl groups containing eight or more carbon atoms may produce perfluorooctanoic acid (PFOA) through metabolism or decomposition. PFOA is "persistent in the environment," "highly bioaccumulative," "toxic to humans and other living organisms," and "long-range transportable," and is therefore listed in "Annex A (Elimination)" of the international treaty "Stockholm Convention on Persistent Organic Pollutants (POPs)."

[0004] Therefore, with the aim of reducing the burden on the environment, Patent Documents 3 and 4 propose anti-fogging agents having perfluoroalkyl groups with 6 or less carbon atoms that do not produce PFOA even when metabolized and / or decomposed.

[0005] However, the European Commission points out in its "COMMISSION STAFF WORKING DOCUMENT" [Poly- and perfluoroalkyl substances (PFAS) Accompanying the document COMMISSION FROM THE COMMISSION TO THE EUROPEAN PARLIAMENT, THE COUNCIL, THE EUROPEAN ECONOMIC AND SOCIAL COMMITTEE AND THE COMMITTEE OF THE REGIONS] that short-chain per- and polyfluoroalkyl substances (PFASs) are less likely to bioaccumulate than PFOA, but are just as persistent in the environment as PFOA.

[0006] Therefore, there is a demand for anti-fogging agents that do not fall under the category of per- and polyfluoroalkyl substances (PFASs), which are persistent in the environment, have a high bioaccumulation potential, and are toxic to humans and other living organisms, i.e., do not contain perfluoroalkyl groups. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 59-093739 [Patent Document 2] Patent No. 5139068 [Patent Document 3] Patent No. 5764729 [Patent Document 4] Patent No. 5621775 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention aims to provide an anti-fog agent that does not have a perfluoroalkyl group and that can suppress the generation of fog (particularly, sustainably suppress the generation of fog) inside a greenhouse by adding it to an agricultural film, and an agricultural film to which the anti-fog agent has been added. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems and have found that the above problems can be solved by using polydimethylsiloxane having polyethylene oxide and propylene oxide attached to both ends. That is, the present invention encompasses the following [1] to [6]. [1] General formula (1) in which ethyleneoxy groups and propyleneoxy groups are added to both ends of polydimethylsiloxane [ka] [In the formula, C2H4O represents an ethyleneoxy group, C3H6O represents a propyleneoxy group, and the ethyleneoxy groups and propyleneoxy groups may be added in a block or random manner, a, b, m, and n represent the average number of moles of each unit added, a and b are the same or different and represent an integer of 1 or more, and m and n are integers of 1 or more.] An anti-fogging agent for agricultural films, which has as its active ingredient a polydimethylsiloxane modified at both ends with polyether, having an HLB value of 5.3 or more and less than 7, and a mass average molecular weight of 3,600 or more and less than 7,000, and has a structure represented by the following formula: [2] An agricultural film containing the anti-fogging agent for agricultural films described in [1] above. [3] The agricultural film according to the above [2], further comprising an anti-fogging agent. [4] Use of the polydimethylsiloxane modified at both ends with polyether according to [1] above for anti-fogging agricultural films. [5] Use of the polydimethylsiloxane modified at both ends with polyether according to [1] above in an agricultural film. [6] Use of the polydimethylsiloxane modified at both ends with polyether and the anti-fogging agent described in [1] above in an agricultural film. [Effects of the Invention]

[0010] The active ingredient of the present invention, a polydimethylsiloxane modified at both ends with polyether, can be added to agricultural films to provide anti-fogging effects. Furthermore, even when an anti-fogging agent such as a nonionic surfactant, such as a sorbitan fatty acid ester, is also added to the agricultural film, the anti-fogging effect can be maintained without being affected. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below. The active ingredient of the present invention, a polydimethylsiloxane modified at both ends with polyether, is, for example, a compound represented by the general formula (2): [ka] [In the formula, m represents the average number of moles added and is an integer of 1 or more.] A silicon-bonded hydrogen atom-containing polyorganosiloxane represented by the general formula (3) [ka] [In the formula, C2H4O represents an ethyleneoxy group, C3H6O represents a propyleneoxy group, the ethyleneoxy groups and propyleneoxy groups may be added in block form or random form, and a, b, and n represent the average number of moles of each unit added and are integers of 1 or greater.] The compound can be obtained by subjecting an oxyalkylene group-containing organic compound represented by the following formula (I) to an addition reaction in the presence of an addition reaction catalyst.

[0012] The polydimethylsiloxane modified at both ends with polyether used in the present invention is represented by the following general formula (1). [ka] In the formula, C2H4O represents an ethyleneoxy group. C3H6O represents a propyleneoxy group. The ethyleneoxy groups and propyleneoxy groups may be added in a block fashion or randomly. a, b, m, and n represent the average number of moles of each unit added. a and b may be the same or different and represent an integer of 1 or more. a is not particularly limited as long as it is an integer of 1 or more, but for example, the lower limit may be 1, 3, 5, 7, 10, 12, etc., and the upper limit may be 50, 40, 30, 25, etc. Specifically, it may be 1 to 50, 3 to 50, 5 to 40, 7 to 40, 10 to 30, 12 to 30, 12 to 25, etc. Although b is not particularly limited as long as it is an integer of 1 or more, for example, the lower limit may be 1, 3, 5, 7, 10, etc., and the upper limit may be 50, 40, 30, 25, etc. Specifically, it may be, for example, 1 to 50, 3 to 50, 5 to 40, 7 to 40, 10 to 30, 10 to 25, etc. m is not particularly limited as long as it is an integer of 1 or more, but for example, the lower limit may be 1, 3, 5, 7, 8, etc., and the upper limit may be 50, 41, 40, 35, 30, etc. Specifically, it may be, for example, 1 to 50, 3 to 41, 5 to 40, 7 to 35, 8 to 30, etc. There are no particular limitations on n as long as it is an integer of 1 or more, but it may be, for example, 1 to 10, 1 to 8, 1 to 6, 1 to 4, etc., and 3 is preferred.

[0013] The content of the polydimethylsiloxane modified at both ends with polyether, which is the active ingredient of the present invention, can be determined, for example, using an HLC-8320GPC (model: manufactured by Tosoh Corporation) as a GPC apparatus, TSKgel SuperMultiporeHZ-M (4 columns) (trade name: manufactured by Tosoh Corporation) as separation columns, a column temperature of 40°C, tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as the mobile phase, a development rate of 0.35 ml / min, and a differential refractometer as the detector.

[0014] The oxyalkylene group-containing organic compound represented by general formula (3) is represented by the formula: n H 2nis a divalent hydrocarbon group, and examples thereof include a methylene group, an ethylene group, a propylene group, an isopropylene group, an n-butylene group, an arylene group, etc. Among these, a methylene group is preferred, and in this case, the oxyalkylene group-containing organic compound is represented by the general formula (4): [ka] [In the formula, C2H4O represents an ethyleneoxy group, C3H6O represents a propyleneoxy group, the ethyleneoxy groups and propyleneoxy groups may be added in a block or random manner, and a and b represent the average number of moles of each unit added and are integers of 1 or greater.] It is shown as follows. Such an oxyalkylene group-containing organic compound can be produced, for example, by adding an alkali catalyst such as sodium hydroxide to allyl alcohol, followed by blowing in ethylene oxide gas or propylene oxide gas to cause addition polymerization. The alkali catalyst used in this process is preferably neutralized with an acid and then completely removed by means of filtration or the like. Furthermore, since the oxyalkylene group-containing organic compound obtained by this method has a wide molecular weight distribution, it is preferable to further fractionate it by rectification.

[0015] In the above-mentioned addition reaction for obtaining the polydimethylsiloxane modified at both ends with polyether, which is the active ingredient of the present invention, the amount of the oxyalkylene group-containing organic compound blended is usually preferably 1.2 to 1.6 moles, and more preferably 1.3 to 1.5 moles, of the oxyalkylene group-containing organic compound per mole of silicon-bonded hydrogen atoms in the silicon-bonded hydrogen atom-containing polyorganosiloxane.

[0016] The addition reaction of the silicon-bonded hydrogen atom-containing polyorganosiloxane and the oxyalkylene group-containing organic compound in the present invention typically proceeds by heating at a temperature of 70 to 120°C for 1 to 2 hours. The addition reaction catalyst used here is not particularly limited, but examples include platinum-based catalysts, rhodium-based catalysts, and palladium-based catalysts. Among these, platinum-based catalysts are preferred, and examples include chloroplatinic acid, fine particle platinum, fine particle platinum adsorbed on a carbon powder carrier, and platinum alumina. The amount of this addition reaction catalyst added is preferably such that the metal amount is 5 to 100 ppm (by weight) of the total amount of reactants.

[0017] The HLB (Hydrophile-Lipophile Balance) value of the polydimethylsiloxane modified at both ends with polyether, which is the active ingredient of the present invention, can be calculated by the following formula, and from the viewpoint of exerting and maintaining sufficient anti-fogging performance, it is not particularly limited as long as it is 5.3 or more and less than 7, but it may be 5.4 or more and 6.9 or less, or 5.4 or more and 6.8 or less, etc., and is preferably 5.5 or more and less than 6.5. Furthermore, a value in this range is also preferred because, when used in combination with an anti-fogging agent, the anti-fogging effect can be maintained without being affected.

[0018] HLB value = 20 × Mw / M Mw: Mass average molecular weight of the hydrophilic portion (ethylene oxide group) M: Total mass average molecular weight

[0019] The mass average molecular weight of the polydimethylsiloxane modified at both ends with polyether, an active ingredient of the present invention, can be determined by gel permeation chromatography (GPC) in terms of styrene as follows: Using an HLC-8320GPC (model: Tosoh Corporation) as the GPC apparatus and TSKgel SuperMultiporeHZ-M (four columns) (trade name: Tosoh Corporation) as the separation columns, the column temperature was set to 40°C, the mobile phase was tetrahydrofuran (Fujifilm Wako Pure Chemical Industries, Ltd.), the development rate was 0.35 ml / min, the sample concentration was 5.5 g / L, the sample injection volume was 20 μL, and a differential refractometer was used as the detector. Using PStQuick MP-M (trade name: Tosoh Corporation) as the standard polystyrene, the mass average molecular weight can be determined in terms of polystyrene molecular weight according to the general-purpose calibration procedure.

[0020] The mass average molecular weight of the polydimethylsiloxane modified at both ends with polyether, which is the active ingredient of the present invention, is not particularly limited as long as it is 3,600 or more and less than 7,000, but may be 3,600 or more and 6,700 or less, 3,600 or more and 6,500 or less, or 3,700 or more and 6,500 or less, and is preferably 4,000 or more and less than 6,000. A mass average molecular weight of 3,600 or more is preferred in that sustained anti-fogging performance can be obtained, and a mass average molecular weight of less than 7,000 is preferred in that bleeding of the anti-fogging agent occurs and anti-fogging performance can be obtained.

[0021] The proportion (mass %) of polydimethylsiloxane modified at both ends with polyether contained in the anti-fogging agent for agricultural films of the present invention is not particularly limited as long as the effects of the present invention are achieved, but is preferably, for example, 10 to 99 mass %, 30 to 90 mass %, 50 to 80 mass %, etc.

[0022] In addition to the active ingredient, polyether-terminated polydimethylsiloxane, the anti-fog agent for agricultural films of the present invention can contain various commonly used resin additives, provided that the effects of the present invention are not impaired. Examples of such resin additives include lubricants, antistatic agents, weather resistance improvers (such as ultraviolet absorbers and hindered amine light stabilizers), plasticizers, antioxidants (including heat stabilizers), dyes, pigments, heat retaining agents, and antiblocking agents.

[0023] The anti-fog agent for agricultural films of the present invention is incorporated into agricultural films. Specifically, the anti-fog agent is added to an agricultural film base resin, such as polyethylene, and then mixed and melted. The resulting mixture is then processed into a film by known methods, such as inflation molding or calendar molding, to produce an agricultural film. The amount of the anti-fog agent for agricultural films of the present invention added is preferably 0.05 to 2 parts by mass, more preferably 0.1 to 0.5 parts by mass, of the active ingredient, polydimethylsiloxane, modified at both ends with polyether, per 100 parts by mass of the agricultural film base resin. An amount of 0.05 parts by mass or more provides sufficient anti-fog effect, while an amount of 2 parts by mass or less is preferred in that it suppresses surface stickiness due to film clouding or excessive bleed-out, making it less susceptible to dust and dirt adhesion.

[0024] The anti-fog agent for agricultural films of the present invention can also be used in combination with an anti-fog agent. Anti-fog agents that can be used in the present invention are not particularly limited, but may be commonly used anti-fog agents, such as polyhydric alcohol fatty acid esters such as sorbitan fatty acid esters, glycerin fatty acid esters, and polyglycerin fatty acid esters (e.g., diglycerin fatty acid esters), or alkylene oxide adducts thereof. More specifically, sorbitan fatty acid ester-based compounds such as sorbitan laurate, sorbitan palmitate, sorbitan stearate, sorbitan oleate, or their polyethylene oxide adducts or polypropylene oxide adducts; glycerin fatty acid ester-based compounds such as glycerin laurate, glycerin palmitate, glycerin stearate, glycerin oleate, or their polyoxyethylene adducts or polypropylene oxide adducts; and diglycerin fatty acid ester-based compounds such as diglycerin laurate, diglycerin palmitate, diglycerin stearate, diglycerin oleate, or their polyoxyethylene adducts or polypropylene oxide adducts. The amount of these anti-fogging agents added is preferably 0.3 to 3 parts by mass, more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the agricultural film base resin.

[0025] An agricultural film containing the antifogging agent for agricultural films of the present invention is also one aspect of the present invention.

[0026] Agricultural film materials that can be used for the agricultural film of the present invention are generally those that have the film-forming ability to be melt-molded at about 150 to 250°C, and any of those generally used for agricultural covering materials can be used, such as vinyl chloride resins such as vinyl chloride resin, ethylene resins such as polyethylene, ethylene-vinyl acetate copolymer, and ethylene-α-olefin copolymer, and propylene resin, with vinyl chloride resins and ethylene resins being preferred. However, the synthetic resins that can be used as agricultural film materials for the agricultural film of the present invention are not limited to these resins.

[0027] The agricultural film of the present invention can contain various commonly used resin additives, such as lubricants, antistatic agents, weather resistance improvers (e.g., ultraviolet absorbers, hindered amine light stabilizers), plasticizers, antioxidants (including heat stabilizers), dyes, pigments, heat retaining agents, antiblocking agents, etc., in amounts generally used, without impairing the effects of the present invention or the respective functions of the various resin additives.

[0028] The agricultural film of the present invention can be produced by any known method, such as an extrusion method (such as a T-die method or an inflation molding method) or a calendar roll molding method. The film thickness is not particularly limited, but is adjusted to, for example, 20 to 1000 μm, preferably 50 to 300 μm. The film may be formed from one or more layers (e.g., three layers), such as an outer layer, an intermediate layer, and an inner layer. When the film is formed from multiple layers, the anti-fog agent for agricultural films of the present invention may be blended in any of the layers. For example, blending in the inner layer is preferred, since a sufficient anti-fog effect can be obtained with a small amount. When an anti-fog agent is blended in the film, the anti-fog agent may be blended in any of the layers, but blending in the intermediate and / or inner layer is preferred, since the anti-fog effect can be maintained without affecting the anti-fog effect.

[0029] The anti-fog property is evaluated, for example, by a known method for evaluating anti-fog property (for example, a method for evaluation with the naked eye). For the agricultural film of the present invention, the anti-fog effect is preferably such that, after a certain period of time (for example, 5 days, 30 days, 60 days, or 90 days) has elapsed since the agricultural film was applied to a greenhouse, no fog is observed inside the greenhouse, or only a small amount of fog is observed near the inner surface of the film, or fog is observed throughout the greenhouse but can be clearly seen 10 m ahead inside the greenhouse.

[0030] The anti-fogging property is evaluated, for example, by a known method for evaluating anti-fogging property [for example, a method for evaluation with the naked eye, a method for evaluation using an image analyzer (for example, "AFA-2" manufactured by Kyowa Interface Science Co., Ltd.)]. With regard to the agricultural film of the present invention, the anti-fogging property is preferably such that, for example, after a certain period (for example, 5 days, 30 days, 60 days, or 90 days) has elapsed since the agricultural film was applied to a greenhouse, no water droplets are visible on the film surface inside the greenhouse, or only large water droplets are visible in some areas.

[0031] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. [Example]

[0032] 1. Preparation of Anti-fogging Agent [Example 1] A 5000 ml three-necked round-bottom flask was charged with 454.6 g of a hydrogen-bonded polydimethylsiloxane in which m in general formula (2) is 17 and 1545.4 g of an oxyalkylene group-containing organic compound in which a and b in general formula (4) are 16, followed by the addition of 1000 g of toluene and homogeneous mixing. 200 mg of chloroplatinic acid was then added and stirred at 90°C for 3 hours. The toluene was then removed using an evaporator to obtain anti-mist agent A. Anti-mist agent A contained 78 mass% of a polydimethylsiloxane modified at both ends with polyether containing a compound represented by the following chemical structure. The HLB value of the polydimethylsiloxane modified at both ends with polyether was 6.0 and the mass-average molecular weight was 4700. [ka]

[0033] [Example 2] A 5000 ml three-necked round-bottom flask was charged with 619.8 g of a hydrogen-bonded polydimethylsiloxane in which m is 18 in general formula (2) and 1380.2 g of an oxyalkylene group-containing organic compound in which a is 12 and b is 10 in general formula (4), followed by the addition of 1000 g of toluene and homogeneous mixing. 200 mg of chloroplatinic acid was then added and stirred at 90°C for 3 hours. The toluene was then removed using an evaporator to obtain anti-mist agent B. Anti-mist agent B contained 78 mass% of a polydimethylsiloxane modified at both ends with polyether containing a compound represented by the following chemical structure. The HLB value of the polydimethylsiloxane modified at both ends with polyether was 5.7 and the mass-average molecular weight was 3700. [ka]

[0034] [Example 3] A 5000 ml three-necked round-bottom flask was charged with 572.2 g of a hydrogen-bonded polydimethylsiloxane in which m in general formula (2) is 30 and 1427.8 g of an oxyalkylene group-containing organic compound in which a and b in general formula (4) are 20, followed by the addition of 1000 g of toluene and homogeneous mixing. 200 mg of chloroplatinic acid was then added and stirred at 90°C for 3 hours. The toluene was then removed using an evaporator to obtain anti-mist agent C. Anti-mist agent C contained 78 mass% of a polydimethylsiloxane modified at both ends with polyether containing a compound represented by the following chemical structure. The HLB value of the polydimethylsiloxane modified at both ends with polyether was 5.4 and the mass-average molecular weight was 6500. [ka]

[0035] [Example 4] A 5000 ml three-necked round-bottom flask was charged with 297.1 g of a hydrogen-bonded polydimethylsiloxane in which m in general formula (2) is 8 and 1702.8 g of an oxyalkylene group-containing organic compound in which a and b in general formula (4) are 14, followed by the addition of 1000 g of toluene and homogeneous mixing. 200 mg of chloroplatinic acid was then added and stirred at 90°C for 3 hours. The toluene was then removed using an evaporator to obtain anti-mist agent D. Anti-mist agent D contained 78 mass% of a polydimethylsiloxane modified at both ends with polyether containing a compound represented by the following chemical structure. The HLB value of the polydimethylsiloxane modified at both ends with polyether was 6.8 and the mass-average molecular weight was 3600. [ka]

[0036] [Example 5] A 5000 ml three-necked round-bottom flask was charged with 320.2 g of a hydrogen-bonded polydimethylsiloxane in which m in general formula (2) is 17 and 1679.8 g of an oxyalkylene group-containing organic compound in which a and b in general formula (4) are 25, followed by the addition of 1000 g of toluene and homogeneous mixing. 200 mg of chloroplatinic acid was then added and stirred at 90°C for 3 hours. The toluene was then removed using an evaporator to obtain anti-mist agent E. Anti-mist agent E contained 78 mass% of a polydimethylsiloxane modified at both ends with polyether containing a compound represented by the following chemical structure. The HLB value of the polydimethylsiloxane modified at both ends with polyether was 6.7 and the mass-average molecular weight was 6500. [ka]

[0037] [Comparative Example 1] A 5000 ml three-necked round-bottom flask was charged with 642 g of a hydrogen-bonded polydimethylsiloxane in which m is 12 in general formula (2) and 1358 g of an oxyalkylene group-containing organic compound in which a and b are 7 in general formula (4), followed by the addition of 1000 g of toluene and homogeneous mixing. 200 mg of chloroplatinic acid was then added and stirred at 90°C for 3 hours. The toluene was then removed using an evaporator to obtain anti-mist agent F. Anti-mist agent F contained 78 mass% of a polydimethylsiloxane modified at both ends with polyether containing a compound represented by the following chemical structure. The HLB value of the polydimethylsiloxane modified at both ends with polyether was 4.9 and the mass-average molecular weight was 2500. [ka]

[0038] Comparative Example 2 A 5000 ml three-necked round-bottom flask was charged with 650.1 g of a hydrogen-bonded polydimethylsiloxane in which m in general formula (2) is 42 and 1349.9 g of an oxyalkylene group-containing organic compound in which a and b in general formula (4) are 23, followed by the addition of 1000 g of toluene and homogeneous mixing. 200 mg of chloroplatinic acid was added and stirred at 90°C for 3 hours. The toluene was then removed using an evaporator to obtain anti-mist agent G. Anti-mist agent G contained 78 mass% of a polydimethylsiloxane modified at both ends with polyether containing a compound represented by the following chemical structure. The HLB value of the polydimethylsiloxane modified at both ends with polyether was 5.1 and the mass-average molecular weight was 8000. [ka]

[0039] Comparative Example 3 A 5000 ml three-necked round-bottom flask was charged with 168.3 g of a hydrogen-bonded polydimethylsiloxane in which m is 3 in general formula (2) and 1831.7 g of an oxyalkylene group-containing organic compound in which a and b in general formula (4) are 13, followed by the addition of 1000 g of toluene and homogeneous mixing. 200 mg of chloroplatinic acid was then added and stirred at 90°C for 3 hours. The toluene was then removed using an evaporator to obtain anti-mist agent H. Anti-mist agent H contained 78 mass% of a polydimethylsiloxane modified at both ends with polyether containing a compound represented by the following chemical structure. The HLB value of the polydimethylsiloxane modified at both ends with polyether was 7.5 and the mass-average molecular weight was 3000. [ka]

[0040] Comparative Example 4 A 5000 ml three-necked round-bottom flask was charged with 272.3 g of a hydrogen-bonded polydimethylsiloxane in which m in general formula (2) is 18 and 1727.7 g of an oxyalkylene group-containing organic compound in which a and b in general formula (4) are 32, followed by the addition of 1000 g of toluene and homogeneous mixing. 200 mg of chloroplatinic acid was then added and stirred at 90°C for 3 hours. The toluene was then removed using an evaporator to obtain anti-mist agent I. Anti-mist agent I contained 78 mass% of a polydimethylsiloxane modified at both ends with polyether containing a compound represented by the following chemical structure. The HLB value of the polydimethylsiloxane modified at both ends with polyether was 7.0 and the mass-average molecular weight was 8000. [ka]

[0041] Comparative Example 5 A 5000 ml three-necked round-bottom flask was charged with 349.1 g of a hydrogen-bonded polydimethylsiloxane in which m is 6 in general formula (2) and 1650.9 g of an oxyalkylene group-containing organic compound in which a and b are 9 in general formula (4), followed by the addition of 1000 g of toluene and homogeneous mixing. 200 mg of chloroplatinic acid was then added and stirred at 90°C for 3 hours. The toluene was then removed using an evaporator to obtain anti-mist agent J. Anti-mist agent J contained 78 mass% of a polydimethylsiloxane modified at both ends with polyether containing a compound represented by the following chemical structure. The HLB value of the polydimethylsiloxane modified at both ends with polyether was 6.4 and the mass-average molecular weight was 2500. [ka]

[0042] Comparative Example 6 A 5000 ml three-necked round-bottom flask was charged with 347.5 g of a hydrogen-bonded polydimethylsiloxane in which m in general formula (2) is 23 and 1652.5 g of an oxyalkylene group-containing organic compound in which a and b in general formula (4) are 30, followed by the addition of 1000 g of toluene and homogeneous mixing. 200 mg of chloroplatinic acid was then added and stirred at 90°C for 3 hours. The toluene was then removed using an evaporator to obtain anti-mist agent K. Anti-mist agent K contained 78 mass% of a polydimethylsiloxane modified at both ends with polyether containing a compound represented by the following chemical structure. The HLB value of the polydimethylsiloxane modified at both ends with polyether was 6.6 and the mass-average molecular weight was 8000. [ka]

[0043] Comparative Example 7 In a 5000 ml three-necked round-bottom flask, add the following [ka] 435.7 g of a hydrogen-bonded polydimethylsiloxane represented by the formula (4) and 1564.3 g of an oxyalkylene group-containing organic compound in which a and b in general formula (4) are 16 were charged, followed by the addition of 1000 g of toluene and uniform mixing, followed by the addition of 200 mg of chloroplatinic acid and stirring at 90°C for 3 hours. The toluene was then removed using an evaporator to obtain anti-mist agent L. Anti-mist agent L contained 78 mass% of polydimethylsiloxane containing a compound represented by the following chemical structure, and the polydimethylsiloxane had an HLB value of 6.0 and a mass average molecular weight of 4700. [ka]

[0044] 2. Preparation of agricultural film <1> material 1) Metallocene PE (trade name: Kernel KF270; ethylene-α-olefin copolymer; manufactured by Japan Polychem Corporation) 2) EVA1 (trade name: V206; ethylene-vinyl acetate copolymer; vinyl acetate content 6% by weight; MFR 2 g / 10 min; manufactured by Ube Maruzen Polyethylene Co., Ltd.) 3) EVA2 (trade name: V215; ethylene-vinyl acetate copolymer; vinyl acetate content 15% by weight; MFR 2 g / 10 min; manufactured by Ube Maruzen Polyethylene Co., Ltd.) 4) Heat retaining agent (trade name: DHT4A; hydrotalcite; manufactured by Kyowa Chemical Industry Co., Ltd.) 5) Ultraviolet absorber (product name: CYASORB UV-531; manufactured by SOLVAY) 6) Light stabilizer (trade name: CHIMASSORB944FDL; manufactured by BASF) 7) Anti-fogging agent (trade name: Rikemal KF-650; a sorbitan fatty acid ester compound; manufactured by Riken Vitamin Co., Ltd.) 8) Anti-fog agent A to L

[0045] <2> Production method A 100mmφ three-layer die (Placo) was used as a three-layer inflation molding machine, with 30mmφ extruders (Placo) for the inner and outer tube layers and a 40mmφ extruder (Placo) for the middle layer. The inner and outer layer extruder temperature was 180°C, the middle layer extruder temperature was 170°C, the die temperature was 180-190°C, the blow ratio was 2.0-3.0, the take-up speed was 3-7 m / min, and the thickness was 100μm (outer layer 20μm, middle layer 60μm, inner layer 20μm). Multilayer agricultural polyolefin films consisting of three layers, outer layer, middle layer, and inner layer, containing the materials listed in Table 1 were obtained [Agricultural Films 1-5 and 14 (Examples), Agricultural Films 6-12 (Comparative Examples), and Agricultural Film 13 (Reference Example)]. The numerical values ​​for each material in Tables 1 and 2 indicate parts by mass.

[0046] [Table 1]

[0047] [Table 2]

[0048] 3. Fog generation test The multilayer agricultural polyolefin film obtained above was sewn to the specified size for use in a greenhouse. A greenhouse was constructed in a field in Shandong Province, China, and the film was stretched so that the inner layer of the film was in contact with the inside of the greenhouse. The greenhouse was constructed with dimensions of 3.6m width, 1.7m ridge height, 1.4m eave height, and 10m depth. The stretching period began in October. Komatsuna was cultivated in the greenhouse from October onwards, and the fog generation status inside the greenhouse was observed and evaluated with the naked eye. The fog generation status was evaluated 5, 30, 60, and 90 days after the film was applied to the greenhouse. The fog generation evaluation was carried out at 5:00 a.m. At the same time, the adhesion of water droplets to the film surface inside the greenhouse (anti-fogging properties) was also evaluated with the naked eye. The degree of fog generation in the greenhouse and the anti-fogging properties were evaluated according to the following evaluation criteria. The results are shown in Table 3.

[0049] <Fog generation evaluation criteria> ⊚: No fog was observed inside the greenhouse, or only a small amount was observed near the inner surface of the film. ○: Fog is occurring throughout the greenhouse, but it is clearly visible 10m ahead inside the greenhouse. △: The fog was rather thick throughout the greenhouse, making it impossible to clearly see what was 5m ahead inside the greenhouse. ×: Thick fog occurred throughout the greenhouse, making it impossible to see anything 2.5 m ahead inside the greenhouse.

[0050] <Evaluation criteria for anti-fogging properties> ◎: No water droplets are observed. ○: Large water droplets are observed in some areas. △: Small water droplets are observed in some areas. ×: Completely cloudy.

[0051] [Table 3]

[0052] As is clear from the above results, anti-fog agents A to E for agricultural films of the present invention, which contain as their active ingredient a polydimethylsiloxane modified at both ends with polyether, having the structure of general formula (1), an HLB value of 5.3 to less than 7, and a mass-average molecular weight of 3,600 to less than 7,000, exhibit excellent, sustained anti-fog properties without affecting the anti-fogging effect. In contrast, agents having the structure of general formula (1) but with an HLB value of less than 5.3 or 7 or greater (anti-fog agents F to I), agents having an HLB value of 5.3 to less than 7 but with a mass-average molecular weight of less than 3,600 or 7,000 or greater (anti-fog agents J and K), and agents having an HLB value of 5.3 to less than 7 and a mass-average molecular weight of 3,600 to less than 7,000 but not having the structure of general formula (1) (anti-fog agent L) exhibited poor anti-fog properties. Therefore, the present invention makes it possible to provide an agricultural film that has low risk of environmental pollution and human health damage caused by fluorochemical surfactants, has excellent anti-fog properties, and maintains other required performances.

Claims

1. An anti-fogging agent for agricultural films, comprising as an active ingredient a polydimethylsiloxane modified at both ends with polyether, which has a structure represented by the following general formula (1) in which an ethyleneoxy group and a propyleneoxy group are attached to both ends of a polydimethylsiloxane, and which has an HLB value of 5.3 or more but less than 7 and a mass average molecular weight of 3,600 or more but less than 7,000: 【Chemical 1】 [In the formula, C ２ H ４ O represents an ethyleneoxy group, and C ３ H ６ O represents a propyleneoxy group, the ethyleneoxy groups and propyleneoxy groups may be added in a block form or in a random form, a, b, m, and n represent the average number of moles of each unit added, a and b are the same or different and represent an integer of 1 or more, and m and n are integers of 1 or more.

2. An agricultural film containing the anti-fogging agent for agricultural films according to claim 1.

3. The agricultural film according to claim 2, further comprising an anti-fogging agent.

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