JP5571019B2 - Agricultural film - Google Patents

Description

  The present invention relates to an agricultural film, and more particularly to an agricultural film suitable for an agricultural greenhouse house or a tunnel covering material capable of maintaining excellent antifogging properties for a long period of time.

  Greenhouse cultivation is widely used as a cultivation method for supplying various crops such as vegetables, fruits and flowers throughout the year. As the coating material, films made of polyvinyl chloride, polyethylene, ethylene-vinyl acetate copolymer, etc. have been widely used. However, in recent years, polyolefin resin films have been used rapidly from the viewpoint of environmental protection. It is widespread.

  However, because the surface of the polyolefin-based resin film is hydrophobic, moisture condenses on the inner surface of the greenhouse of the film depending on the weather conditions, depending on the moisture given to the crop and the moisture from the crop itself, and countless small water droplets. Occur. In such a state, the transmission of sunlight during the day is hindered, leading to a shortage of temperature rise in the greenhouse, or water drops falling and causing damage to crops.

  In order to prevent such harm, a method of kneading and mixing a polyhydric alcohol fatty acid ester as an antifogging agent is generally employed. By this method, the water condensed on the film surface forms a water film without forming water droplets, so that the water droplets are prevented from falling. However, as the moisture flows, the antifogging agent on the film surface is washed away, making it difficult to develop long-term antifogging durability. In order to solve this problem, if an anti-fogging agent with a slow bleed property is used or if the amount of the anti-fogging agent is increased, it may be necessary to age for a long time before anti-fogging is exhibited, There were problems such as excessive whitening of the agent and whitening of the film surface or stickiness.

  As a method for preventing whitening and stickiness due to such excessive bleeding, Patent Literature 1 and Patent Literature 2 include a method of mixing a slow-acting sorbitan antifogging agent and a fast-acting glycerin antifogging agent in a specific ratio. Is disclosed. However, with this method, it is difficult to prevent the above problems, and it has not been possible to satisfy both whitening and anti-fogging sustainability at the same time.

  Furthermore, Patent Document 3 discloses a method of mixing a polyhydric alcohol ester of a hydroxy fatty acid with a nonionic surfactant. However, even with this method, there has been a problem that sufficient whitening improvement cannot be obtained or the anti-fogging sustainability is lowered. Patent Document 4 discloses a method of mixing a straight-chain paraffin sulfonic acid metal salt with a polyhydric alcohol saturated fatty acid ester. However, when a straight-chain paraffinsulfonic acid metal salt is added, the bleed-out property of the surfactant is remarkably lowered, so that there is a problem that the initial antifogging property and the antifogging durability are remarkably lowered.

JP-A-3-59046 Japanese Unexamined Patent Publication No. 3-59047 JP-A-60-26048 Japanese Patent Laid-Open No. 10-35

  The present invention provides an agricultural film that is less likely to be whitened by bleed-out of an antifogging agent and excellent in initial antifogging property and antifogging durability.

  The agricultural film of the present invention contains 100 parts by weight of an ethylene-vinyl acetate copolymer, 0.005 to 2 parts by weight of exfoliated graphite, and 1 to 5 parts by weight of an antifogging agent.

  If the content of the vinyl acetate component of the ethylene-vinyl acetate copolymer is small, the polarity of the ethylene-vinyl acetate copolymer will be low and the antifogging agent may not be sufficiently contained. Since the amount of the antifogging agent that bleeds out from the agricultural film is too small and the antifogging property of the agricultural film may be lowered, it is preferably 1 to 10% by weight, more preferably 3 to 8% by weight.

  Also, if the melt flow rate (MFR) of the ethylene-vinyl acetate copolymer is low, the flexibility of the agricultural film may be reduced, and if it is high, the transparency of the agricultural film may be reduced. 0.5 to 4 g / 10 min is preferable. In the present invention, the melt flow rate of the ethylene-vinyl acetate copolymer is a temperature of 190 ° C. and a load of 21 in accordance with JIS K 7210 “Testing Method for Melt Mass Flow Rate (MFR) of Plastic-Thermoplastic Plastic”. The value measured under the condition of 18N.

  Agricultural films contain antifogging agents. The antifogging agent is not particularly limited, and for example, polyhydric alcohol saturated fatty acid esters such as sorbitan palmitate, sorbitan stearate, glycerin stearate, diglyceryl stearate, polyglyceryl stearate, sorbitol glyceryl stearate; Examples thereof include polyhydric alcohol unsaturated fatty acid esters such as glycerin oleate and diglycerin oleate, sorbitan palmitate and sorbitan stearate are preferable, and sorbitan palmitate and sorbitan stearate are preferably used in combination. In addition, an antifogging agent may be used independently or 2 or more types may be used together.

  If the content of the antifogging agent in the agricultural film is small, the antifogging property of the agricultural film may be lowered. If the content is large, the bleedout amount of the antifogging agent is excessively increased and the agricultural film is whitened. Therefore, the amount is limited to 1 to 5 parts by weight, preferably 1.3 to 2.5 parts by weight, based on 100 parts by weight of the ethylene-vinyl acetate copolymer.

  Further, exfoliated graphite is contained in the agricultural film. This exfoliated graphite is a laminate of a plurality of graphene sheets. Exfoliated graphite is obtained by exfoliating a graphite compound, and is a laminate of graphene sheets having a thickness smaller than that of a raw material graphite compound, that is, less than the number of laminated graphene sheets of a raw material graphite compound. It is the laminated body of the graphene sheet which has a lamination | stacking number. In the present invention, the graphene sheet refers to a single sheet-like material composed of a carbon hexagonal mesh plane.

  The graphite compound may be either graphite or expanded graphite, but expanded graphite is preferred because it is easily peeled from between the graphene sheets. Note that a functional group may be chemically bonded to graphite, or a functional group may be artificially bonded to graphite due to weak interaction. In the present invention, expanded graphite refers to a material in which an interlayer material is inserted into a raw material graphite and a space between graphene sheets is widened.

  The number of graphene sheets laminated in exfoliated graphite may be 2 to 200 layers as long as it is less than the number of laminated graphite compounds as raw materials. Exfoliated graphite has a scaly shape in which a plurality of thin graphene sheets are laminated and has a relatively large aspect ratio.

  The number of graphene sheets laminated in exfoliated graphite is preferably 150 layers or less, more preferably 60 layers or less, still more preferably 30 layers or less, particularly preferably 10 layers or less, and most preferably 5 layers or less. In addition, the number of graphene sheets stacked in exfoliated graphite can be measured using a transmission electron microscope (TEM), and is an arithmetic average value of the number of graphene sheets stacked in each exfoliated graphite.

  Further, the aspect ratio of exfoliated graphite is preferably 20 or more, more preferably 50 or more, particularly preferably 100 or more, and most preferably 200 or more, but if it is too high, cracking of exfoliated graphite may occur. 5000 or less is preferable. The aspect ratio of exfoliated graphite refers to the arithmetic average value of the aspect ratios of each exfoliated graphite by calculating the aspect ratio obtained by dividing the maximum dimension in the plane direction of the graphene sheet by the thickness for each exfoliated graphite.

  Here, the maximum dimension of the exfoliated graphite in the plane direction of the graphene sheet refers to the maximum dimension of the exfoliated graphite when viewed from the direction in which the area of the exfoliated graphite is the largest. The thickness of exfoliated graphite refers to the maximum dimension of exfoliated graphite in the direction orthogonal to the surface of exfoliated graphite when viewed from the direction in which the area of exfoliated graphite is the largest.

  In addition, the maximum dimension in the surface direction of a graphene sheet in exfoliated graphite can be measured using FE-SEM. Moreover, the thickness of exfoliated graphite can be measured using a transmission electron microscope (TEM) or FE-SEM.

  If the content of exfoliated graphite in the agricultural film is small, the bleed-out of the antifogging agent will be excessive and whitening of the agricultural film will occur, and if it is large, the transparency of the agricultural film will decrease. -It is limited to 0.005-2 weight part with respect to 100 weight part of vinyl acetate copolymers, and 0.02-0.07 weight part is preferable.

  As described above, exfoliated graphite is obtained by exfoliating a graphite compound, and has a scaly shape with a relatively large aspect ratio. Most of exfoliated graphite is the main component of graphene sheets. It is contained in a state where the surface is aligned with the front and back surfaces of the agricultural film. In addition, the main surface of a graphene sheet means a surface with the largest area.

  And, on the way that the antifogging agent contained in the agricultural film bleeds out on the surface of the agricultural film, the exfoliated graphite has an effect of stopping the progress of the antifogging agent, and the antifogging agent is contained in the exfoliated graphite. The antifogging agent held in the micropores present in the flake graphite is then gradually released to bleed out on the surface of the agricultural film. Accordingly, the antifogging agent in the agricultural film bleeds out to the surface of the agricultural film at a slower rate than when exfoliated graphite is not present. In addition, as described above, the antifogging agent is retained in the fine pores of exfoliated graphite, and the antifogging agent is gradually released from the fine pores. An agent can be included. That is, although the agricultural film of the present invention contains a large amount of an antifogging agent, the speed at which the antifogging agent bleeds out to the surface of the agricultural film is adjusted by the presence of exfoliated graphite. As a result, an appropriate amount of the antifogging agent can be stably bleed out over a long period of time on the surface of the agricultural film.

  In addition, exfoliated graphite can adjust the speed at which the antifogging agent bleeds out to the surface of the agricultural film with a small amount, and as a result, the agricultural film of the present invention has excellent transparency, Sufficient transmission of sunlight can be secured to ensure the cultivation of crops.

  Next, a method for producing exfoliated graphite contained in an agricultural film will be described. Exfoliated graphite is produced by exfoliating a graphite compound, and the method for producing exfoliated graphite is not particularly limited, but exfoliated graphite is preferably produced by the following method.

  First, a graphite sheet or an expanded graphite sheet is used as a working electrode, and the working electrode is immersed in an acidic electrolyte aqueous solution together with a reference electrode made of Pt or the like and subjected to electrochemical treatment. Thereby, an acidic electrolyte ion can be intercalated between graphite sheets, that is, graphene sheets of layered graphite, and the interval between the graphene sheets can be widened.

  Specifically, as shown in FIG. 1, a sheet 1 made of graphite or expanded graphite is prepared. A plurality of slits 1a and 1b are formed in the sheet 1 as shown in FIG. The sheet 1 is a laminate of a plurality of graphene sheets G as schematically shown. The plurality of slits 1a and 1b penetrating in the thickness direction of the sheet 1 which is perpendicular to the surface direction of the graphene sheet G are formed. The slits 1a and 1b can be formed by mechanical cutting or laser light irradiation. The number of slits is not particularly limited.

  Next, part of the electrode 2 is inserted into the slits 1a and 1b. The electrode 2 includes insertion pieces 2a and 2b that are inserted into the slits 1a and 1b, respectively, and a connecting portion 2c that connects the insertion pieces 2a and 2b. The electrode 2 is made of Pt in the present embodiment, but can be formed of an appropriate metal.

  Insert pieces 2a and 2b of the electrode 2 are inserted into the slits 1a and 1b. As a result, a structure in which a part of the electrode 2 is inserted into the sheet 1 can be obtained as shown in FIG. This structure is immersed in an aqueous electrolyte solution as shown in FIG.

  As the electrolyte solution 6, an aqueous nitric acid solution, an aqueous sulfuric acid solution, or the like can be used. Thereby, nitrate ions or sulfate ions can be inserted between the graphene sheets.

  The sheet 1 immersed in the electrolyte solution 6 is used as a working electrode, and a counter electrode 7 made of a metal such as Pt and a reference electrode 8 made of Ag / AgCl are immersed in the electrolyte solution 6. Electrochemical treatment is performed with a DC voltage applied between them. As a result, the electrolyte ions in the electrolyte solution 6 are intercalated between the graphene sheets of the sheet 1. In addition, a gap between the graphene sheets of the sheet 1 is widened.

  In the electrochemical treatment, a DC voltage of preferably 0.3 to 10 V is applied between the counter electrode 7 and the sheet 1 for 1 hour or more and less than 500 hours. If the DC voltage range is within this range, electrolyte ions such as nitrate ions and sulfate ions can be more reliably intercalated between graphene sheets of graphite compounds, and expanded graphite can be obtained more reliably. Can do. The DC voltage application time may be one hour or longer, but if it is too long, the productivity of expanded graphite is reduced and the effect of intercalating electrolyte ions is saturated. Therefore, the DC voltage application time may be less than 500 hours.

  The concentration of the electrolyte solution 6 is not particularly limited, but is preferably 10 to 80% by weight in the case of an aqueous solution. Within this range, electrolyte ions can be intercalated between the graphene sheets more reliably.

  The temperature of the electrolyte solution 6 during the electrochemical treatment is not particularly limited, but in the case of an aqueous solution, the temperature may be about 5 to 100 ° C.

  More preferably, prior to forming the slits 1a and 1b in the sheet 1 made of a graphite compound, it is preferable to prepare a sheet 1 having a lower density. In order to prepare such a sheet 1 having a lower density, for example, the following method can be used. First, a raw material powder of a graphite compound is preliminarily formed into a sheet to obtain a pre-formed sheet. As shown in FIG. 4, the preformed sheet 11 is fed between rolls 12 and 13 and rolled. Thereby, a sheet 1 thinner than the preformed sheet 11 can be obtained. In this case, the density of the sheet 1 can be adjusted by adjusting the rolling ratio. That is, by reducing the rolling ratio, a sheet-like graphite compound having a relatively low density can be obtained.

  As described above, when the sheet 1 made of a graphite compound and having a low density is used, the electrolyte ions as the interlayer material are uniformly intercalated between the graphene sheets of the graphite compound, and the interlayer between the graphenes is more reliably expanded. be able to.

  The expanded graphite obtained as described above has the uniformity of the angle formed between the main surfaces of the graphene sheets by intercalating nitrate ions and the like, and the uniformity of the amount of intercalation material inserted between the graphene sheets. Are better. Therefore, the graphene sheets of expanded graphite can be easily separated from each other by applying a peeling force to the obtained expanded graphite. When there is a variation in the amount of intercalation material inserted between the graphene sheets of expanded graphite, there is a portion where the graphene sheets cannot be peeled apart, particularly when a peeling force by heat is applied. On the other hand, the expanded graphite obtained as described above is excellent in the uniformity of the amount of intercalation material inserted between the graphene sheets, so that a peeling force for peeling the graphene sheets was applied. In this case, the graphene sheet can be reliably peeled off from other graphene sheets between almost all graphene sheets. Therefore, exfoliated graphite can be easily obtained by applying a peeling force for peeling the graphene sheets to the expanded graphite obtained by the above manufacturing method.

  The exfoliation process for obtaining exfoliated graphite from expanded graphite can be performed by performing a kind of energy application process selected from the group consisting of heating, mechanical exfoliation force, ultrasonic waves, and the like.

  As an example, exfoliated graphite can be obtained from expanded graphite by heating expanded graphite to 300 to 1200 ° C., preferably 300 to 600 ° C.

  In addition, in the said agricultural film, if it is in the range which does not impair the effect of this invention, an inorganic heat retention agent, an organic heat retention agent, a light stabilizer, antioxidant, a ultraviolet absorber, an antifog agent, a lubricant, a pigment, etc. These additives may be added.

  The inorganic heat-retaining agent is added for the purpose of improving the heat retention of agricultural films and preventing extrusion fluctuations during film formation of agricultural films. Such an inorganic heat insulating agent is not particularly limited. For example, magnesium oxide, calcium oxide, aluminum oxide, magnesium carbonate, calcium carbonate, magnesium sulfate, calcium sulfate, aluminum sulfate, lithium phosphate, calcium phosphate, magnesium silicate, silicic acid. Calcium, aluminum silicate, kaolin, clay, talc, hydrotalcite, lithium aluminum composite hydroxide, alkali metal, alkaline earth metal, transition metal, group 12 (group 2B) element, group 14 other than carbon ( 4B)) or a composite hydroxide having at least two elements selected from elements. These may be used alone or in combination of two or more.

  As the light stabilizer, conventionally known light stabilizers can be used. Among these, hindered amine light stabilizers are preferable. Examples of the hindered amine light stabilizer include dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine 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] } Etc., and 2 or more types may be used together.

  And as said antioxidant, although a conventionally well-known thing can be used, what has the effect as a heat stabilizer is preferable. Examples of such antioxidants include chelators such as metal salts of carboxylic acids, phenolic antioxidants, and organic phosphites, and these may be used alone or in combination of two or more. .

  As the ultraviolet absorber, conventionally known ones can be used, for example, 2,4-dihydroxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2 ′. -Benzophenone ultraviolet absorbers such as dihydroxy-4-methoxybenzophenone, 2,2'-hydroxy-4,4'-dimethoxybenzophenone, 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 ′) Benzotriazole ultraviolet rays such as 5′-di-tert-butylphenyl) -5-chlorobenzotriazole and 2- (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole Absorbers, salicylic acid ester ultraviolet absorbers, cyanoacrylate ultraviolet absorbers and the like may be mentioned, and these may be used alone or in combination of two or more.

  And as said fog prevention agent, a conventionally well-known thing can be used, For example, surfactants, such as silicone type and a fluorine type, are mentioned. As the lubricant, conventionally known ones can be used, and examples thereof include saturated fatty acid amides such as stearic acid amide, unsaturated fatty acid amides such as erucic acid amide and oleic acid amide, and bisamides such as ethylene bis stearic acid amide. .

  Furthermore, if the thickness of the agricultural film of the present invention is thin, the tear strength and impact strength of the agricultural film may be reduced, and if it is thick, it becomes difficult to cut, join and stretch the agricultural film. Therefore, 50 to 200 μm is preferable, and 70 to 170 μm is more preferable.

  Next, the manufacturing method of the agricultural film of this invention is demonstrated. As a method for producing an agricultural film, a known method is used. For example, (1) ethylene-vinyl acetate copolymer, exfoliated graphite and antifogging agent, and other additives are supplied to an extruder and melted. Kneading and extruding a cylindrical body from a circular die attached to the tip of the extruder, sending compressed air from the center of this cylindrical body to expand to a certain size, and blowing cooling air to the outer surface of the cylindrical body And after cooling, the cylindrical body is cut from a predetermined location and developed to produce an agricultural film, (2) an ethylene-vinyl acetate copolymer, exfoliated graphite and an antifogging agent, and Other additives may be supplied to an extruder, melt kneaded, and extruded from a T die attached to the tip of the extruder to produce an agricultural film. Inflation film molding method is preferable.

  When producing an agricultural film as described above, exfoliated graphite is subjected to a shearing force in the extrusion direction when passing through a circular die or a T die, and the main surface of the graphene sheet faces the surface of the agricultural film. Oriented. Therefore, the obtained agricultural film contains exfoliated graphite in a state where the main surface of the graphene sheet is substantially along the surface of the agricultural film, and the exfoliated graphite has a small amount of antifogging agent. The speed of traveling through the agricultural film can be reduced to an appropriate speed.

  In addition, although the case where exfoliated graphite was supplied to the extruder was described above, expanded graphite was supplied to the extruder instead of exfoliated graphite or together with exfoliated graphite, and the peeling force applied to the expanded graphite in the extruder. And exfoliating the graphene sheets of expanded graphite to produce exfoliated graphite in an extruder, and extruding the exfoliated graphite with a polyethylene resin from a circular die or T die to produce an agricultural film. Also good.

  Although the case where the agricultural film is a single layer has been described above, a multilayer agricultural film may be used. Specifically, as shown in FIG. 5, the multilayer agricultural film A is composed of 100 parts by weight of an ethylene-vinyl acetate copolymer, 0.005 to 2 parts by weight of exfoliated graphite, and 1 to 5 of an antifogging agent. The intermediate layer A1 containing parts by weight, and laminated and integrated on one surface of the intermediate layer A1, contains 100 parts by weight of an ethylene-vinyl acetate copolymer and 0.1 to 0.8 parts by weight of an antifogging agent. The first surface layer A2 does not contain exfoliated graphite, and the second surface layer A3 is laminated and integrated on the other surface of the intermediate layer A1 and contains linear low-density polyethylene. The exfoliated graphite and the antifogging agent constituting the intermediate layer A1 are the same as in the case of a single-layer agricultural film, and thus the description thereof is omitted.

  If the content of the antifogging agent in the intermediate layer A1 is small, the antifogging property of the agricultural film may be lowered. Therefore, the amount is limited to 1 to 5 parts by weight, preferably 1.3 to 2.5 parts by weight, based on 100 parts by weight of the ethylene-vinyl acetate copolymer.

  If the content of exfoliated graphite in the intermediate layer A1 is small, the bleed-out of the antifogging agent will be excessive and whitening of the agricultural film will occur, and if it is large, the transparency of the agricultural film will decrease. The amount is limited to 0.005 to 2 parts by weight, preferably 0.06 to 2 parts by weight, based on 100 parts by weight of the ethylene-vinyl acetate copolymer.

  Also, if the melt flow rate of the ethylene-vinyl acetate copolymer constituting the intermediate layer A1 is low, the flexibility of the agricultural film may decrease, and if it is high, the transparency of the agricultural film decreases. Therefore, 0.5 to 4 g / 10 min is preferable.

  The first surface layer A2 laminated and integrated on one surface of the intermediate layer A1 contains an antifogging agent. The antifogging agent is not particularly limited, and for example, polyhydric alcohol saturated fatty acid esters such as sorbitan palmitate, sorbitan stearate, glycerin stearate, diglyceryl stearate, polyglyceryl stearate, sorbitol glyceryl stearate; Examples thereof include polyhydric alcohol unsaturated fatty acid esters such as glycerin oleate and diglycerin oleate, sorbitan palmitate and sorbitan stearate are preferable, and sorbitan palmitate and sorbitan stearate are preferably used in combination. In addition, an antifogging agent may be used independently or 2 or more types may be used together.

  If the content of the antifogging agent contained in the first surface layer A2 is small, the antifogging property of the agricultural film may be lowered, and if it is large, the bleedout amount of the antifogging agent is excessively increased. Since whitening may occur in the agricultural film, it is limited to 0.1 to 0.8 parts by weight, preferably 0.2 to 0.5 parts by weight, based on 100 parts by weight of the ethylene-vinyl acetate copolymer.

  The first surface layer A2 does not contain exfoliated graphite, and the antifogging agent contained in the first surface layer A2 is inhibited by the exfoliated graphite from bleeding out on the surface of the agricultural film. Never happen.

  As described above, the intermediate layer A1 contains exfoliated graphite, and the intermediate layer A1 is configured so that the speed at which the antifogging agent travels through the intermediate layer A1 is slow, while the first surface layer A2 Does not adopt a structure that slows the progress of the antifogging agent. Furthermore, the amount of the antifogging agent contained in the intermediate layer A1 is configured to be larger than the amount of the antifogging agent contained in the first surface layer A2.

  That is, although the multilayer agricultural film A contains a large amount of the antifogging agent in the intermediate layer A1, the speed of bleeding out of the antifogging agent in the intermediate layer A1 is suppressed as described above. Furthermore, the concentration gradient of the antifogging agent between the intermediate layer A1 and the first surface layer A2 ensures the transition from the intermediate layer A1 to the first surface layer A2 in contact with the intermediate layer A1. The antifogging agent transferred from the intermediate layer A1 to the first surface layer A2 proceeds through the first surface A2 without being inhibited by exfoliated graphite, and smoothly bleeds out to the surface of the agricultural film. Thus, although the multilayer agricultural film A contains a large amount of antifogging agent in the intermediate layer A1, the supply amount per unit time from the intermediate layer A1 to the first surface layer A2 does not become excessive. The anti-fogging agent that has been transferred to the first surface layer A2 is configured so that the supply from the intermediate layer A1 to the first surface layer A2 is performed stably over a long period of time. In order to smoothly bleed out on the surface of the agricultural film A, an appropriate amount of the antifogging agent is always bleed out on the surface of the agricultural film A, and the bleedout of the antifogging agent is also stable over a long period of time. Therefore, the agricultural film of the present invention has little whitening due to bleed-out of the antifogging agent and is excellent in initial antifogging property and antifogging durability.

  And if there is little content of the vinyl acetate component of the ethylene-vinyl acetate copolymer which comprises intermediate | middle layer A1, the polarity of an ethylene-vinyl acetate copolymer will become low and will fully contain an antifogging agent. When the amount of the antifogging agent bleed out from the agricultural film is too small, the antifogging property of the agricultural film may be reduced. 18-22 weight% is more preferable.

  On the other hand, if the content of the vinyl acetate component of the ethylene-vinyl acetate copolymer constituting the first surface layer A2 is small, the polarity of the ethylene-vinyl acetate copolymer will be low, and the antifogging agent will be sufficient. In some cases, the amount of the antifogging agent that bleeds out from the agricultural film may be too small and the antifogging property of the agricultural film may be lowered. Preferably, 4 to 8% by weight is more preferable.

  In this way, in the multilayer agricultural film, by increasing the content of the vinyl acetate component of the ethylene-vinyl acetate copolymer constituting the intermediate layer A1, the ethylene- It is preferable that the vinyl acetate copolymer is made highly polar so that a polar antifogging agent can be easily contained in the intermediate layer A1, and the intermediate layer A1 can contain a large amount of antifogging agent.

  On the other hand, by reducing the content of the vinyl acetate component of the ethylene-vinyl acetate copolymer constituting the first surface layer A2, the ethylene-vinyl acetate copolymer constituting the first surface layer A2 is reduced. It is preferable that the polarity is lowered and the antifogging agent that has entered the first surface layer A2 is smoothly bleed out from the first surface layer A2.

  When the content of the vinyl acetate component of the ethylene-vinyl acetate copolymer is adjusted as described above, the intermediate layer A1 has a higher affinity with the antifogging agent than the first surface layer A2, The antifogging agent that has reached the interface between the layer A1 and the first surface layer A2 is different from the intermediate layer A1 than the difference in the affinity for the ethylene-vinyl acetate copolymer between the intermediate layer A1 and the first surface layer A2. In order to be greatly affected by the concentration gradient of the antifogging agent between the first surface layer A2 and the antifogging agent in the intermediate layer A1, when reaching the interface between the intermediate layer A1 and the first surface layer A2, the intermediate layer The anti-fogging agent incorporated into the first surface layer A2 without staying in the A1 and the antifogging agent incorporated into the first surface layer A2 is the same as the ethylene-vinyl acetate copolymer constituting the first surface layer A2. Since the affinity is relatively low and there is no exfoliated graphite, the surface of the agricultural film is smoothly bleed out. To.

  A second surface layer A3 containing linear low-density polyethylene is laminated and integrated on the other surface of the intermediate layer A1 constituting the agricultural film A. The linear low-density polyethylene constituting the second surface layer A3 is extremely low in polarity and therefore lacks affinity with the antifogging agent, and the antifogging agent contained in the intermediate layer A1 is the intermediate layer A1. Therefore, the antifogging agent contained in the intermediate layer A1 can be smoothly transferred to the first surface layer A2 side.

  The second surface layer A3 preferably does not contain exfoliated graphite because the transparency of the agricultural film may be reduced. The second surface layer A3 preferably contains no antifogging agent in order to improve the antifouling property of the agricultural film.

  Furthermore, if the thickness of the multi-layer agricultural film of the present invention is thin, the tear strength and impact strength of the agricultural film may decrease, and if it is thick, it is difficult to cut, bond and stretch the agricultural film. Therefore, the handleability may be lowered, so 50 to 200 μm is preferable, and 70 to 170 μm is more preferable.

  Next, the manufacturing method of the multilayer agricultural film is demonstrated. The film forming method of the multilayer agricultural film A is not particularly limited. For example, a film forming apparatus in which three extruders are connected to one circular die via a connector is prepared. The resin composition for the intermediate layer A1, the first surface layer A2, or the second surface layer A3 is supplied to the three extruders of the membrane apparatus, melted and kneaded in each extruder, and then the molten resin composition The product is supplied to the circular die and co-extruded into a cylindrical shape from the circular die, and the compressed air is supplied from the center of the circular die to form the co-extruded resin composition by air-cooled inflation film molding. And winding it up.

  In addition, although the case where exfoliated graphite was supplied to the extruder was described above, expanded graphite was supplied to the extruder instead of exfoliated graphite or together with exfoliated graphite, and the peeling force applied to the expanded graphite in the extruder. And exfoliating the graphene sheets of expanded graphite to produce exfoliated graphite in an extruder, and extruding the exfoliated graphite with a polyethylene resin from a circular die or T die to produce an agricultural film. Also good.

  The agricultural film of the present invention contains 100 parts by weight of an ethylene-vinyl acetate copolymer, 0.005 to 2 parts by weight of exfoliated graphite, and 1 to 5 parts by weight of an antifogging agent. A large amount of antifogging agent can be stably bleed out from the beginning of use over a long period of time, and is excellent in initial antifogging property and antifogging durability.

  In addition, exfoliated graphite takes a scale-like form with a large aspect ratio, and the amount of exfoliated graphite necessary to reduce the speed at which the antifogging agent proceeds in the agricultural film can be reduced. The agricultural film of the present invention has excellent transparency, and can sufficiently ensure the transmission of sunlight and ensure the cultivation of crops.

  Furthermore, the agricultural film of the present invention comprises an intermediate layer containing 100 parts by weight of an ethylene-vinyl acetate copolymer, 0.005 to 2 parts by weight of exfoliated graphite and 1 to 5 parts by weight of an antifogging agent, and this intermediate layer. A first surface layer containing 100 parts by weight of an ethylene-vinyl acetate copolymer and 0.1 to 0.8 parts by weight of an antifogging agent and not containing exfoliated graphite; And a second surface layer containing a linear low density polyethylene on the other side of the intermediate layer, so that the intermediate layer contains a large amount of anti-fogging agent and the first at an appropriate supply rate. The antifogging agent can be supplied to the surface layer, and the antifogging agent can be bleed out from the initial stage of use to the surface of the agricultural film with an appropriate amount through the first surface layer for a long period of time. Therefore, the agricultural film of the present invention has little initial whitening due to bleeding out of the antifogging agent and excellent initial antifogging properties and antifogging durability.

  In the agricultural film, a second surface layer A3 containing linear low density polyethylene is laminated and integrated on the other surface of the intermediate layer, and the linear low density constituting the second surface layer is integrated. Polyethylene has a very low polarity and therefore lacks affinity with the antifogging agent. The antifogging agent contained in the intermediate layer hardly transfers to the second surface layer, and is contained in the intermediate layer. The anti-fogging agent can be smoothly transferred to the first surface layer side, and the anti-fogging agent can be surely bleed out from the surface of the first surface layer with an appropriate amount.

It is a typical perspective view for demonstrating the process of inserting an electrode in graphite. It is a typical perspective view which shows the state by which the electrode was inserted in graphite. It is a schematic diagram for demonstrating the process of performing an electrochemical process. It is the schematic diagram which showed the process of rolling the sheet | seat consisting of the graphite used as a raw material, and obtaining sheet-like graphite. It is sectional drawing which showed an example of the agricultural film of this invention. It is the figure which showed the voltage application pattern at the time of applying a voltage to a graphite sheet by an electrochemical process.

  Next, examples of the present invention will be described, but the present invention is not limited to the following examples.

(Examples 1-4, Comparative Examples 1-3)
Graphite powder was preliminarily formed into a sheet to produce a preformed sheet. As shown in FIG. 4, this preformed sheet was supplied between rolls 12 and 13 and rolled to prepare a low-density graphite sheet having a density of 0.7 g / cm ³ and a thickness of 1 mm.

The graphite sheet having a density of 0.7 g / cm ³ obtained as described above was cut into a flat square shape having a side of 3 cm to obtain a graphite sheet as an electrode material. In this graphite sheet, as shown in FIG. 2, two slits were formed by cutting with a cutter knife such that the slit length was 1 cm and the width was 1 cm. The electrode 2 made of Pt shown in FIG. 2 was inserted into the graphite sheet on which the two slits were formed. The graphite sheet thus prepared was immersed in a 60 wt% nitric acid aqueous solution together with a reference electrode (cathode) made of Pt and a reference electrode made of Ag / AgCl as a working electrode (anode), and a DC voltage was applied. Electrochemical treatment was performed. In the electrochemical treatment, the voltage shown in FIG. 6 was applied for 2 hours. Thus, the graphite used as the working electrode for the anode was used as expanded graphite.

  The obtained expanded graphite was cut into a flat square shape having a side of 1 cm to produce a cut piece, and the cut piece was placed in a carbon crucible and subjected to electromagnetic induction heat treatment. As the induction heating apparatus, an apparatus commercially available from SK Medical Co., Ltd. under the trade name “MU1700D” was used, and the current was 10 A so that the maximum temperature reached 550 ° C. in an argon gas atmosphere. Exfoliated graphite was exfoliated by electromagnetic induction heating to obtain exfoliated graphite.

  A film forming apparatus in which a circular die is connected to the tip of the extruder is prepared, and an ethylene-vinyl acetate copolymer (trade name “VF105S” manufactured by Ube Maruzen Polyethylene Co., Ltd.) is added to the extruder of this film forming apparatus. Ingredient: 5% by weight, melt flow rate: 1.0 g / 10 min) 100 parts by weight, light stabilizer (trade name “TINUVIN 783” manufactured by BASF Japan Ltd.) 0.4 parts by weight, Mg—Al infrared absorber (Kyowa) 4 parts by weight of chemical industry trade name “DHT-4A”) and a predetermined amount of sorbitan palmitate (trade name “P-300” manufactured by Riken Vitamin Co., Ltd.) shown in Table 1, sorbitan stearate (RIKEN Vitamin Co., Ltd.) Product name “S-300W”), glyceryl stearate (trade name “S-100” manufactured by Riken Vitamin Co., Ltd.), diglycerin stearate (RIKEN Vitamin Co., Ltd.) (Product name “S-72”) and the above exfoliated graphite are supplied and melt-kneaded in the extruder, and then the molten resin composition is supplied from the extruder to the circular die to extrude the cylindrical body from the circular die, 25 ° C compressed air is sent from the center of the cylindrical body to expand it to a certain size, and after cooling by blowing 20 ° C cooling air onto the outer surface of the cylindrical body, the cylindrical body is cut from a predetermined location. Then, an agricultural film having a thickness of 100 μm was obtained.

(Examples 5-8, Comparative Examples 4-6)
A film forming apparatus is prepared in which three extruders are connected to one circular die via a connector, and the first extruder of the film forming apparatus is used as an extruder for the intermediate layer A1, and ethylene-vinyl acetate. Copolymer (trade name “VF120S” manufactured by Ube Maruzen Polyethylene Co., Ltd., vinyl acetate component: 20% by weight, melt flow rate: 0.8 g / 10 min), 100 parts by weight, light stabilizer (trade name “TINUVIN 783 manufactured by BASF Japan Ltd.) ] 0.27 parts by weight, 3 parts by weight of an Mg-Al infrared absorber (trade name “DHT-4A” manufactured by Kyowa Chemical Industry Co., Ltd.), and a predetermined amount of sorbitan palmitate (Riken Vitamin Co., Ltd.) shown in Table 2 Product name “P-300”), sorbitan stearate (trade name “S-300W” manufactured by Riken Vitamin Co., Ltd.), glyceryl stearate (product name “S-100” manufactured by Riken Vitamin Co., Ltd.) , Diglycerin stearate (trade name “S-72” manufactured by Riken Vitamin Co., Ltd.) and a resin composition containing exfoliated graphite produced in Example 1 were supplied, and the second extruder was used for extrusion for the first surface layer A2. As a machine, ethylene-vinyl acetate copolymer (trade name “VF105S” manufactured by Ube Maruzen Polyethylene Co., Ltd., vinyl acetate component: 5% by weight, melt flow rate: 1.0 g / 10 min), 100 parts by weight, light stabilizer (BASF) 0.1 part by weight of a product name “TINUVIN 783” manufactured by Japan, 1 part by weight of an Mg—Al infrared absorber (trade name “DHT-4A” manufactured by Kyowa Chemical Industry Co., Ltd.), and a predetermined amount shown in Table 1 Sorbitan palmitate (trade name “P-300” manufactured by Riken Vitamin Co., Ltd.), sorbitan stearate (trade name “S-300W” manufactured by Riken Vitamin Co., Ltd.), glyceryl stearate (RIKEN Vita Product name “S-100”) and diglycerin stearate (trade name “S-72”, manufactured by Riken Vitamin Co., Ltd.), and a third extruder for the second surface layer A2. As an extruder, 100 parts by weight of linear low density polyethylene (trade name “Elite 5100” manufactured by Dow Chemical Co., Ltd., melt flow rate: 0.85 g / 10 min) and a light stabilizer (trade name “TINUVIN 783 manufactured by BASF Japan Ltd.) are used. )) After supplying 0.03 parts by weight and melt-kneading in each extruder, the molten resin composition is supplied from the first to third extruders to the circular die, and the first surface layer A2, intermediate The layer A1 and the second surface layer A3 are co-extruded into a cylindrical shape from a circular die so that they are laminated and integrated in this order, and compressed air at 25 ° C. is supplied from the center of the circular die and is cylindrical. body After cooling by cooling air at 20 ° C. on the outer surface, the coextruded resin composition is formed into a film by air-cooled inflation film, and the formed film is wound up to form a second surface layer A3, an intermediate layer An agricultural film having a thickness ratio of A1 and first surface layer A2 of 15/65/20 and a total thickness of 100 μm was obtained.

  The whitening property, initial antifogging property and antifogging durability of the obtained agricultural film were measured in the following manner, and the results are shown in Tables 1 and 2.

(Whitening)
The agricultural film immediately after production is left in a thermostat maintained at 40 ° C. for one month, and then the haze value of the agricultural film is measured using a haze meter (trade name “NDH2000” manufactured by Nippon Denshoku Industries Co., Ltd.). And evaluated based on the following criteria.
A Haze value was less than 10%.
○: The haze value was 10% or more and less than 15%.
Δ: Haze value was 15% or more and less than 25%.
X: The haze value was 25% or more.

(Initial anti-fogging property)
After supplying a predetermined amount of water at 20 ° C. into the aquarium, the agricultural film is placed at the opening of the aquarium so that the first surface layer faces the inside of the aquarium and does not contact the water in the aquarium. The opening of the water tank was completely closed by stretching. The ambient temperature in which the water tank was left was 0 ° C.

After leaving in this state for 3 hours, the agricultural film was visually observed and evaluated based on the following criteria.
◎ ・ ・ ・ There were no water droplets on the surface of the agricultural film, and the water in the tank was visible.
○ Water droplets were attached to part of the surface of the agricultural film, but there were no water droplets flowing on the surface of the agricultural film, and the water in the aquarium was visible.
Δ: Water droplets adhered to the surface of the agricultural film, and some of the water droplets flowed on the surface of the agricultural film.
×: Water droplets adhered to the entire surface of the agricultural film, and the water in the aquarium could not be seen.

(Anti-fog durability)
After supplying a predetermined amount of water at 20 ° C. into the aquarium, the agricultural film is placed at the opening of the aquarium so that the first surface layer faces the inside of the aquarium and does not contact the water in the aquarium. The opening of the water tank was completely closed by stretching. The ambient temperature in which the water tank was left was 0 ° C.

After leaving in this state for 600 hours, the agricultural film is visually observed, and the ratio of the area where water droplets adhere to the surface portion of the agricultural film facing the water in the aquarium is calculated. And evaluated based on the following criteria.
A: The ratio of the area where water droplets adhered was 0%.
○: Although water droplets adhered to the surface of the agricultural film, the proportion of the area where the water droplets adhered was less than 30%.
Δ: Water droplets adhered to the surface of the agricultural film, and the ratio of the area where the water droplets adhered was 30% or more and less than 60%.
X: Water droplets adhered to the surface of the agricultural film, and the ratio of the area where the water droplets adhered was 60% or more.

1 sheet
1a slit
2a Insertion piece
2c Connecting part 2 Electrode 6 Electrolyte solution 7 Counter electrode 8 Reference electrode
11 Pre-formed sheet
12 Roll A Agricultural film
A1 middle class
A2 First surface
A2 First surface layer
A2 Second surface layer
A3 Second surface layer G Graphene sheet

Claims (3)

An agricultural film comprising 100 parts by weight of an ethylene-vinyl acetate copolymer, 0.005 to 2 parts by weight of exfoliated graphite, and 1 to 5 parts by weight of an antifogging agent. An intermediate layer containing 100 parts by weight of an ethylene-vinyl acetate copolymer, 0.005 to 2 parts by weight of exfoliated graphite and 1 to 5 parts by weight of an antifogging agent, and laminated and integrated on one surface of the intermediate layer, A first surface layer containing 100 parts by weight of an ethylene-vinyl acetate copolymer and 0.1 to 0.8 parts by weight of an antifogging agent and not containing exfoliated graphite is laminated and integrated on the other surface of the intermediate layer. And an agricultural film comprising a second surface layer containing linear low-density polyethylene. The amount of vinyl acetate in the ethylene-vinyl acetate copolymer constituting the intermediate layer is 15 to 25% by weight, and the amount of vinyl acetate in the ethylene-vinyl acetate copolymer constituting the first surface layer The agricultural film according to claim 2, wherein is 1 to 10% by weight.

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