JP2012025037A - Agricultural film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an agricultural film having superior mechanical strength and heat-resistant fusion bonding properties.SOLUTION: A layer (A) including polyethylene-based resin having a density of 0.900 to 0.930 g/cmand a melt flow rate (MFR) of 0.3 to 5.0 g/10 min or ethylene-vinyl acetate copolymer having a vinyl acetate content of 5.0 to 25 wt.% and a MFR of 0.5 to 4.0 g/10 min, a layer (B) including ethylene-vinyl acetate copolymer having a vinyl acetate content of 5.0 to 25 wt.% and a MFR of 0.5 to 4.0 g/10 min, and a layer (C) including a polyethylene-based resin having a density of 0.900 to 0.930 g/cmand a MFR of 0.3 to 5.0 g/10 min are laminated and integrated in this order. At least one of the layer (A) or the layer (C) includes 0.1 to 0.5 pts.wt. silica particles having a particle size of 5 to 10 μm based on 100 pts.wt. resin components included in each layer.

Description

  The present invention relates to an agricultural film used in an agricultural crop cultivation facility (agricultural house). In detail, it is related with the agricultural film extended in the cultivation facility comprised with metal pipes.

  Conventionally, as a means for cultivating agricultural crops, house cultivation using an agricultural house has been actively performed. In the above-mentioned house cultivation, the farm house can be adjusted to conditions suitable for the growth of the crop, protect the crop from the wind and rain, and prevent damage to the crop by flying objects such as stones and dust.

  The agricultural house is formed by spreading and covering an agricultural film on the framework of the house. Conventionally, a polyvinyl chloride film has been frequently used as the agricultural film used here. However, in recent years, agricultural films mainly composed of ethylene-vinyl acetate copolymer have been actively used in consideration of environmental safety.

  As an agricultural film mainly composed of such an ethylene-vinyl acetate copolymer, for example, in Patent Document 1, the outer layer of the film is mainly a resin composition comprising an ethylene-α-olefin copolymer and high-density polyethylene. The film intermediate layer is composed mainly of a resin composition containing an ethylene-vinyl acetate copolymer and inorganic fine particles containing at least one atom of Mg, Ca, Al, Si, Li, and the film inner layer is A three-layer agricultural film mainly composed of an ethylene-vinyl acetate copolymer is disclosed.

  Patent Document 2 discloses a three-layer laminated film in which the inner and outer layers of the film are layers made of an ethylene-vinyl acetate copolymer, and the film intermediate layer is obtained by copolymerization with a metallocene catalyst. It is a layer mainly composed of a resin composition containing an olefin copolymer, an ethylene-vinyl acetate copolymer, and inorganic fine particles containing at least one atom of Mg, Ca, Al, Si, and Li. An agricultural film characterized by the above is disclosed.

  Further, in Patent Document 3, the first layer is a layer mainly composed of an ethylene-α-olefin copolymer, and the second layer is an ethylene-α-olefin based on 100 parts by weight of the ethylene-vinyl acetate copolymer. It is a layer made of a resin composition containing 25 to 100 parts by weight of a copolymer, and the third layer is an ethylene-α-olefin copolymer of 0 to 50 with respect to 100 parts by weight of an ethylene-vinyl acetate copolymer. An agricultural film characterized by being a layer made of a resin composition containing parts by weight is disclosed.

  However, the agricultural film mainly composed of an ethylene-vinyl acetate copolymer as described in Patent Documents 1 to 3 is inferior in tear strength and impact strength. Therefore, when a strong wind is blown by a typhoon or the like, the agricultural film is used. The film could not be used for a long period of time because it was torn from the crease part of the film, or the film was broken by flying objects such as stones and dust.

  In addition, the agricultural film is transported or stored after being manufactured or used, in a state of being wound and rolled, or folded into a laminated body. In particular, when the agricultural film is placed in the above-described state in a high temperature environment such as summer, there is a problem that the films cannot be peeled off due to heat fusion. If the agricultural films that have been heat-sealed are forcibly separated from each other, the films may stretch and become white or may be torn. For this reason, an agricultural film excellent in heat-resistant fusing property that does not cause thermal fusing between films even under a high temperature environment is desired.

JP 2000-324957 A JP 2000-238201 A JP 2001-334612 A

  Therefore, an object of the present invention is to provide an agricultural film excellent in mechanical strength and heat-resistant fusing property.

The agricultural film of the present invention has a polyethylene resin having a density of 0.900 to 0.930 g / cm ³ and a melt flow rate (MFR) of 0.3 to 5.0 g / 10 minutes, or vinyl acetate content. A layer (A) comprising an ethylene-vinyl acetate copolymer having a melt flow rate (MFR) of 0.5 to 4.0 g / 10 minutes,
A layer (B) comprising an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5.0 to 25% by weight and a melt flow rate (MFR) of 0.5 to 4.0 g / 10 min, and a density of A layer (C) containing a polyethylene resin having 0.900 to 0.930 g / cm ³ and a melt flow rate (MFR) of 0.3 to 5.0 g / 10 minutes is laminated and integrated in this order. Become
At least one of the layer (A) and the layer (C) contains 0.1 to 0.5 silica particles having an average particle diameter of 5 to 10 μm with respect to 100 parts by weight of the resin component contained in each layer. It includes a weight part.

The agricultural film of the present invention has a polyethylene resin having a density of 0.900 to 0.930 g / cm ³ and a melt flow rate (MFR) of 0.3 to 5.0 g / 10 minutes, or vinyl acetate content. Is a layer (A) containing an ethylene-vinyl acetate copolymer having a melt flow rate (MFR) of 0.5 to 4.0 g / 10 min, and a vinyl acetate content of 5.0 to 25% by weight. A layer (B) containing an ethylene-vinyl acetate copolymer having a melt flow rate (MFR) of 0.5 to 4.0 g / 10 min, and a density of 0.900 to 0.930 g. / and melt flow rate in cm ³ (MFR) is a layer (C) comprising a polyethylene resin is 0.3 to 5.0 g / 10 min, because the are laminated integrally in this order, tear strength Ya Mechanical strength such as impact strength Excellent in degree. Therefore, the agricultural film of the present invention is preferably used for a long period of time because the crease part of the film is not torn by a strong wind or the like, and the film is hardly broken by flying objects such as stones and dust. can do.

  Moreover, in the agricultural film of the present invention, at least one of the layer (A) or the layer (C) disposed in the outermost layer contains silica particles having a specific size in a specific amount, whereby the surface of the layer Even after storage for a long period of time in a high-temperature environment where the film surface temperature is 40 ° C. or higher, the films are firmly adhered or heat-sealed. Highly suppressed. Therefore, the agricultural film can be easily peeled off without being heat-sealed even after being stored in a roll shape or folded, and can be used for agricultural houses and tunnels. The work of spreading the film can be easily performed. Moreover, when at least one of the layer (A) or the layer (C) contains silica particles having a specific size in a specific amount, it is possible to improve the mechanical strength of the obtained agricultural film.

  Moreover, it is preferable that the white pigment is contained in each layer and the black pigment is contained in the layer (A) and the layer (B). In such a case, an agricultural film in which the layer (C) is white and the layers (A) and (B) are gray is obtained. In the film, part of sunlight is reflected by the layer (C). The sunlight transmitted through the layer (B) is absorbed by the layer (A) and the layer (B), and thus has excellent light shielding properties. Moreover, in the said film, the infrared rays and far infrared rays which are heat rays can also be reflected by making each layer contain a white pigment, and it is excellent also in heat-shielding property.

  Furthermore, since the agricultural film of the present invention does not contain aluminum and is excellent in flexibility, it can be stored compactly.

[Layer (A)]
The layer (A) contains a polyethylene resin or an ethylene-vinyl acetate copolymer as a main component.

  The polyethylene resin is not particularly limited, and examples thereof include low density polyethylene, medium density polyethylene, and ethylene-α-olefin copolymer. Good. Among these polyethylene resins, ethylene-α-olefin copolymers are preferable, and linear low density polyethylene is more preferable.

  The linear low-density polyethylene is obtained by copolymerizing ethylene and α-olefin using a single-site catalyst such as Ziegler catalyst or metallocene catalyst, and adjusting the type and amount of α-olefin. Can control the density range.

  In addition, examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, and the like. Two or more kinds may be used in combination.

  Moreover, it is particularly preferable to use an ethylene-α-olefin copolymer and low-density polyethylene in combination as the polyethylene resin. By using these in combination, the heat-resistant fusing property of the agricultural film can be improved.

When the density of the polyethylene resin is low, blocking and heat fusion occur when the agricultural film is folded and stored, whereas when the density is high, the impact strength of the agricultural film is lowered and it is caused by flying objects. since breaking a film is likely to occur are limited to 0.900~0.930g / cm ^3, preferably 0.905~0.925g / cm ^3, more preferably 0.910~0.920g / cm ³ .

  In addition, the density of the polyethylene-type resin in this invention says the value measured based on JISK7112 "The measuring method of the density and specific gravity of a plastic-non-foamed plastic".

  On the other hand, if the melt flow rate (MFR) of the polyethylene resin is small, the layer (A) and thus the film-forming property of the agricultural film is deteriorated. On the other hand, if the melt flow rate (MFR) is large, the tensile strength of the layer (A) Since mechanical strength falls, it is limited to 0.3-5.0 g / 10min, 0.5-4.5g / 10min is preferable and 0.8-4.0g / 10min is more preferable.

  When the layer (A) contains a plurality of types of polyethylene resins, the density of the polyethylene resins and the melt flow rate (MFR) are the apparent density and melt flow of the mixture of polyethylene resins, respectively. Late (MFR).

  Further, if the content of the vinyl acetate component in the ethylene-vinyl acetate copolymer is small, the impact strength and flexibility of the layer (A) and thus the agricultural film are insufficient, and the agricultural film is stored compactly. On the other hand, if the amount is too large, the layer (A) and, consequently, the film-forming property of the agricultural film is deteriorated or the mechanical strength is lowered, so it is limited to 5.0 to 25% by weight. 5.0 to 20% by weight is preferable.

  On the other hand, when the melt flow rate (MFR) of the ethylene-vinyl acetate copolymer is small, the film-forming property of the layer (A) and thus the agricultural film is deteriorated. On the other hand, when the melt flow rate (MFR) is large, the layer (A) Is reduced to 0.5 to 4.0 g / 10 min, and preferably 0.8 to 2.0 g / 10 min.

  In addition, when the said layer (A) contains multiple types of ethylene-vinyl acetate copolymer, content of the vinyl acetate component of an ethylene-vinyl acetate copolymer and melt flow rate (MFR) are respectively It refers to the apparent vinyl acetate component content and melt flow rate (MFR) of the ethylene-vinyl acetate copolymer mixture.

  Here, the melt flow rate (MFR) of the polyethylene resin and the ethylene-vinyl acetate copolymer in the present invention conforms to JIS K7210 “Testing method for melt mass flow rate and melt volume flow rate of plastic-thermoplastic plastic”. The value measured under conditions of a temperature of 190 ° C. and a load of 21.18N.

  The layer (A) contains one or both of a polyethylene resin and an ethylene-vinyl acetate copolymer as a main component, but preferably contains only a polyethylene resin. The polyethylene-based resin can impart more excellent heat-resistant fusing property to agricultural films.

  The total content of the polyethylene resin and the ethylene-vinyl acetate copolymer in the layer (A) is preferably 60% by weight or more, more preferably 80% by weight or more with respect to all components constituting the layer (A). preferable.

[Layer (B)]
The layer (B) of the agricultural film of the present invention contains an ethylene-vinyl acetate copolymer as a main component. By using an ethylene-vinyl acetate copolymer for the layer (B), the flexibility of the agricultural film can be ensured, and such an agricultural film can be easily folded and stored.

  When the content of the vinyl acetate component in the ethylene-vinyl acetate copolymer is small, there is a problem that the flexibility of the layer (B) and thus the agricultural film is insufficient. On the other hand, when the content is large, the layer (B) and the agriculture are agricultural. The film-forming property of the film for the use deteriorates or the mechanical strength decreases, so the content is limited to 5.0 to 25% by weight, and preferably 10 to 20% by weight.

  On the other hand, when the melt flow rate (MFR) of the ethylene-vinyl acetate copolymer is small, the film-forming property of the layer (B) and thus the agricultural film is deteriorated. On the other hand, when the melt flow rate (MFR) is large, the layer (B) Is reduced to 0.5 to 4.0 g / 10 min, and preferably 0.8 to 2.0 g / 10 min.

  In addition, when multiple types of ethylene-vinyl acetate copolymer is contained in the layer (B), the content of the vinyl acetate component and the melt flow rate (MFR) of the ethylene-vinyl acetate copolymer are ethylene, -The apparent vinyl acetate component content and melt flow rate (MFR) of the mixture of vinyl acetate copolymers.

  The layer (B) contains an ethylene-vinyl acetate copolymer as a main component, but the content of the ethylene-vinyl acetate copolymer in the layer (B) is based on all the components constituting the layer (B). On the other hand, it is preferably 60% by weight or more, more preferably 80% by weight or more.

[Layer (C)]
The layer (C) of the agricultural film of the present invention contains a polyethylene resin as a main component. As this polyethylene-type resin, the same thing as the polyethylene-type resin used for the said layer (A) is used.

  Moreover, it is particularly preferable to use an ethylene-α-olefin copolymer and low-density polyethylene in combination as the polyethylene resin. By using these in combination, the heat-resistant fusing property of the agricultural film can be improved.

When the density of the polyethylene resin is low, blocking and heat fusion occur when the agricultural film is folded and stored, while when it is high, the agricultural film becomes stiff and can be stored compactly. because can not, limited to 0.900~0.930g / cm ^3, preferably ^{0.905~0.925g / cm 3, 0.910~0.920g / cm} 3 is more preferable.

  On the other hand, when the melt flow rate (MFR) of the polyethylene resin is small, the layer (C) and thus the film-forming property of the agricultural film is deteriorated. On the other hand, when it is large, the mechanical strength of the layer (C) and the agricultural film is deteriorated. Therefore, it is limited to 0.3 to 5.0 g / 10 minutes, preferably 0.5 to 4.5 g / 10 minutes, and more preferably 0.8 to 4.0 g / 10 minutes.

  When the layer (C) contains a plurality of types of polyethylene resin, the density of the polyethylene resin and the melt flow rate (MFR) are the apparent density and melt flow of the mixture of polyethylene resins, respectively. Late (MFR).

  The layer (C) contains a polyethylene resin as a main component, but the content of the polyethylene resin in the layer (C) is preferably 60% by weight with respect to all the components constituting the layer (C). Above, more preferably 80% by weight or more.

  In addition, when forming the agricultural film of this invention by coextrusion, from the film forming property of an agricultural film, the polyethylene-type resin in a layer (A) or an ethylene-vinyl acetate copolymer, a layer (B) The ethylene-vinyl acetate copolymer in the layer and the polyethylene resin in the layer (C) are preferably those having mutually close melt flow rate (MFR) values. Specifically, the layer (A ) Of polyethylene-based resin or ethylene-vinyl acetate copolymer in layer), ethylene-vinyl acetate copolymer in layer (B) and polyethylene-based resin in layer (C), the melt flow rate (MFR) is the largest. Preferably, the difference in melt flow rate (MFR) between the one and the smallest is 2.0 g / 10 min or less.

[Silica particles]
In the agricultural film of the present invention, at least one of the layer (A) or the layer (C) contains 0 silica particles having an average particle diameter of 5 to 10 μm with respect to 100 parts by weight of the resin component contained in each layer. 0.1 to 0.5 parts by weight are included.

  In the agricultural film of the present invention, at least one of the layer (A) or the layer (C) arranged in the outermost layer contains silica particles having a specific size in a specific amount, so that the surface of the layer is moderate. Unevenness is formed. When an agricultural film was rolled up or folded into a laminate, the film layer (A) and the other film layer (C) overlapped at the overlapping portion of the films. It becomes a state. Accordingly, by forming appropriate irregularities on the surface of at least one of the layer (A) or the layer (C), the contact area between the layer (A) and the layer (C) is reduced, and the films Can be highly suppressed from being thermally fused. Moreover, when at least one of the layer (A) or the layer (C) contains silica particles having a specific size in a specific amount, it is possible to improve the mechanical strength of the obtained agricultural film.

  Examples of the silica particles include natural silica particles and synthetic silica particles. Examples of natural silica particles include silica sand, shirasu perlite, and the like whose main component is quartz. Examples of the synthetic silica particles include those obtained by a reaction between sodium silicate and an acid, those obtained by hydrolysis of an alkoxysilane, and those obtained by a reaction between calcium silicate and an acid. These silica particles may be used alone or in combination of two or more.

  The average particle diameter of the silica particles is 5 to 10 μm, preferably 5 to 8 μm. Silica particles having an average particle diameter of less than 5 μm are likely to agglomerate and are not highly dispersed in the layer (A) and the layer (C), so that there is a possibility that adhesion between films and thermal fusion cannot be sufficiently suppressed. In addition, silica particles having an average particle diameter exceeding 10 μm may reduce the mechanical strength, transparency, and haze value of the agricultural film.

  The average particle diameter of the silica particles can be measured, for example, from an SEM photograph obtained by photographing the cross section of the agricultural film of the present invention with a transmission electron microscope (SEM) at a magnification of tens of thousands to several hundred thousand times. The projected area circle equivalent diameter of 100 or more silica particles (primary particles) is measured, and the obtained values are arithmetically averaged. The projected area equivalent diameter of silica particles means the diameter of a perfect circle having the same area as the projected area of silica particles. The projected area equivalent circle diameter is not particularly limited, but can be obtained, for example, by analyzing the SEM photographic image obtained above using image processing software (for example, Luzex (registered trademark) AP manufactured by Nireco).

  The silica particles are contained in at least one of the layer (A) and the layer (C), but are preferably contained in at least the layer (A). The layer (A) and the layer (C) More preferably, it is contained in both layers. Thus, by using a silica particle, the outstanding heat-fusion property can be provided to an agricultural film. At this time, it is preferable that the layer (B) does not contain silica particles. When the layer (B) does not contain silica particles, the flexibility of the agricultural film can be improved.

  As for content of the silica particle in each layer of a layer (A) and a layer (C), 0.1-0.5 weight part is preferable with respect to 100 weight part of resin components contained in each layer, and 0.3-0. 5 parts by weight is more preferred. In a layer containing silica particles of less than 0.1 parts by weight, there is a possibility that adhesion between films and thermal fusion cannot be sufficiently suppressed. Moreover, in the layer containing the silica particle exceeding 0.5 weight part, there exists a possibility of reducing the mechanical strength of an agricultural film, transparency, and a haze value.

  In the present invention, the resin component in each layer means all resins contained in each layer. Therefore, in addition to the resin used as the main component, the resin component includes other resins different from the main component by using a masterbatch or the like.

[Pigment]
In the agricultural film of the present invention, the layer (A) contains 5.0 to 30 parts by weight of a white pigment and 0.1 to 5.0 parts by weight of a black pigment with respect to 100 parts by weight of the resin component. B) contains 1.0 to 10 parts by weight of white pigment and 0.1 to 5.0 parts by weight of black pigment with respect to 100 parts by weight of resin component, and layer (C) contains 100 parts by weight of resin component. On the other hand, it is preferable to contain 5.0 to 50 parts by weight of a white pigment and not to contain a black pigment. By adopting such a configuration, it is possible to impart light shielding properties to the agricultural film.

  In recent years, cultivation methods using plant habits have been proposed as plant cultivation methods. As one of such cultivation methods, there is a cultivation method using the photoperiodicity of the plant, and this is adjusted by appropriately adjusting the daylighting from the sun, so that it is not exposed to the sun. This is a method of adjusting the time (dark period) to accelerate or reverse the growth and flowering of flower buds.

  The cultivation method using the photoperiodicity of the above-mentioned plant is used, for example, for cultivation of chrysanthemum that makes flower buds easily attached by extending the dark period. As a method for extending the dark period, a method of covering the agricultural house with a highly light-shielding film in the daytime is employed. Such a light-shielding agricultural film is often rolled up and stored when sunlight is applied to a plant. The rolled-up agricultural film is likely to heat up, and the films are easily heat-sealed.

  The agricultural film of the present invention is particularly preferably used as a light-shielding agricultural film because it contains a pigment and has excellent light-shielding properties and can prevent the occurrence of heat fusion. Moreover, since the white pigment and the black pigment are used without using aluminum in order to impart light shielding properties, it is excellent in flexibility and can be stored compactly.

  The layer (A) contains a white pigment for the purpose of enhancing the light shielding properties and heat shielding properties of the agricultural film. The white pigment is not particularly limited as long as it is a white pigment. For example, rutile titanium oxide, titanium oxide such as anatase titanium oxide, zinc oxide (zinc white), zinc sulfide, lead white, molybdenum white, Among them, titanium oxide having excellent light shielding properties is preferable, and rutile type titanium oxide having particularly excellent light shielding properties is more preferable. In addition, the said white pigment may be used independently or 2 or more types may be used together. In the present invention, white means a color having a brightness of 8 to 10 in the so-called Munsell color system.

  In addition, if the average particle size of the white pigment is small, the white pigment tends to aggregate, making it difficult to uniformly disperse the white pigment in the layer (A), and handling of agricultural films. On the other hand, if it is large, the mechanical strength of the layer (A) and thus the agricultural film may be lowered, so that it is preferably 100 to 300 nm, more preferably 150 to 250 nm.

  In addition, the average particle diameter of the white pigment in the present invention refers to a value measured by a laser diffraction method.

  The content of the white pigment in the layer (A) is preferably 5.0 to 30 parts by weight and more preferably 10 to 25 parts by weight with respect to 100 parts by weight of the resin component. This is because, when the content of the white pigment in the layer (A) is small, the ratio of the black pigment in the layer (A) becomes high, the layer (A) becomes dark, and the color of the layer (C) becomes dark. This is because the heat shielding property of the agricultural film is lowered, while if it is large, the layer (A) and, consequently, the film-forming property and mechanical strength of the agricultural film are lowered.

  The layer (A) contains a black pigment for the purpose of enhancing the light shielding properties of the agricultural film. The black pigment is not particularly limited as long as it is a black pigment, and examples thereof include carbon black and aniline black that are used for paints, pastes, plastics, and the like. Carbon black is preferable from the viewpoint of safety and economy. In addition, the said black pigment may be used independently, or 2 or more types may be used together. In the present invention, black means a color having a lightness of 0 to 2 in the so-called Munsell color system.

  Moreover, 0.1-5.0 weight part is preferable with respect to 100 weight part of resin components, and, as for content of the black pigment in the said layer (A), 0.1-3.0 weight part is more preferable. This is because, when the content of the black pigment in the layer (A) is small, the light shielding property of the agricultural film is deteriorated. On the other hand, when the content is large, the layer (A) becomes dark, and the color of the layer (C) becomes dark. This is because the heat shielding property of the agricultural film is lowered.

  The layer (B) preferably contains a white pigment for the purpose of improving the light shielding and heat shielding properties of the agricultural film. Examples of the white pigment include those similar to the white pigment contained in the layer (A). Among them, titanium oxide having excellent light shielding properties is preferable, and rutile titanium oxide having particularly excellent light shielding properties is more preferable. . In addition, the said white pigment may be used independently, or 2 or more types may be used together.

  In addition, if the average particle size of the white pigment is small, the white pigment tends to aggregate and it becomes difficult to uniformly disperse the white pigment in the layer (B), and the handleability of the agricultural film is low. On the other hand, when it is large, the mechanical strength of the layer (B) and thus the agricultural film may be lowered. Therefore, 100 to 300 nm is preferable, and 150 to 250 nm is more preferable.

  Furthermore, 1.0-10 weight part is preferable with respect to 100 weight part of resin components, as for content of the white pigment in a layer (B), 3.0-8.0 weight part is more preferable, and 4.0-6 0.0 part by weight is particularly preferred. This is because when the content of the white pigment in the layer (B) is small, the proportion of the black pigment in the layer (B) increases, the layer (B) becomes darker, and the color of the layer (C) becomes darker. This is because the heat shielding property of the agricultural film is lowered, whereas if it is large, the layer (B) and, consequently, the film-forming property and mechanical strength of the agricultural film are lowered.

  The layer (B) preferably contains a black pigment for the purpose of enhancing the light shielding properties of the agricultural film. As said black pigment, the same thing as the black pigment contained in the said layer (A) is mentioned, Carbon black is preferable from safety | security and economical efficiency. In addition, the said black pigment may be used independently, or 2 or more types may be used together.

  The content of the black pigment in the layer (B) is preferably 0.1 to 5.0 parts by weight, more preferably 0.5 to 3.0 parts by weight, with respect to 100 parts by weight of the upper resin component. 0.0 to 2.0 parts by weight is particularly preferable. This is because when the content of the black pigment in the layer (B) is small, the light-shielding property of the agricultural film is deteriorated, while when it is large, the layer (B) becomes dark and the color of the layer (C) becomes dark. This is because the heat shielding properties of agricultural films are reduced.

  The layer (C) preferably contains a white pigment for the purpose of improving the light shielding properties and heat shielding properties of the agricultural film. Examples of the white pigment include those similar to the white pigment contained in the layer (A). Among them, titanium oxide having excellent light shielding properties is preferable, and rutile titanium oxide having particularly excellent light shielding properties is more preferable. . In addition, the said white pigment may be used independently or 2 or more types may be used together.

  In addition, if the average particle size of the white pigment is small, the white pigment tends to aggregate, making it difficult to uniformly disperse the white pigment in the layer (C), and handling characteristics of agricultural films. On the other hand, when it is large, the mechanical strength of the layer (C) and thus the agricultural film may be lowered. Therefore, 100 to 300 nm is preferable, and 150 to 250 nm is more preferable.

  The content of the white pigment in the layer (C) is preferably 5.0 to 30 parts by weight, more preferably 10 to 25 parts by weight, and particularly preferably 15 to 20 parts by weight with respect to 100 parts by weight of the resin component. . This is because when the content of the white pigment in the layer (C) is small, the whiteness of the layer (C) becomes insufficient and the heat shielding property of the agricultural film is lowered, whereas when it is large, the layer (C) As a result, the film-forming property and mechanical strength of the agricultural film are lowered.

  The layer (C) preferably contains no black pigment. This is because when the agricultural film contains a black pigment, the whiteness of the layer (C) is impaired, the layer (C) cannot sufficiently reflect infrared rays and far infrared rays, and the heat shielding property of the agricultural film is reduced. It is because it falls.

  When the agricultural film of the present invention is used as a light-shielding agricultural film in a cultivation method utilizing the photoperiodicity of a plant in an agricultural house, the film is sunlight on a plant cultivated in the agricultural house. Is used to prevent irradiation. At this time, the light-shielding agricultural film of the present invention is disposed in an agricultural house with the layer (A) on the inside (plant side).

  In this way, for example, the formation of flower buds is achieved by shielding or adjusting the sunlight irradiated in the agricultural house with an agricultural film, utilizing the photoperiodicity of the plant and adjusting the temperature in the agricultural house. And flowering time can be adjusted.

  On the other hand, when irradiating the plants cultivated in the agricultural house with sunlight, the agricultural film may be removed, and the irradiation and shielding of the sunlight with respect to the plants can be easily adjusted by arranging and removing the agricultural film. can do.

[Nonionic surfactant]
The agricultural film of the present invention preferably contains a nonionic surfactant for the purpose of improving its antifogging property. The nonionic surfactant is not particularly limited as long as it can impart antifogging properties, but a polyhydric alcohol fatty acid ester or an alkylene oxide such as ethylene oxide or propylene oxide is added to the polyhydric alcohol fatty acid ester. An alkylene oxide-added polyhydric alcohol fatty acid ester is preferably used.

  And as said polyhydric alcohol fatty acid ester, it is not specifically limited, Polyhydric alcohol saturated fatty acid ester, such as glycerol stearate ester, diglycerol stearate ester, polyglycerol stearate ester, sorbitol stearate ester; Glycerol oleate And polyhydric alcohol unsaturated fatty acid esters such as diglycerin oleate and the like, and polyhydric alcohol saturated fatty acid esters are preferred.

  Moreover, as said alkylene oxide addition polyhydric alcohol fatty acid ester, what added ethylene oxide and propylene oxide to the above-mentioned polyhydric alcohol fatty acid ester is mentioned.

  And as for the addition mole number of the alkylene oxide in the said alkylene oxide addition polyhydric alcohol fatty acid ester, 0.1-10 mol is preferable. This is because, when the number of moles of alkylene oxide added is small, the antifogging property of the agricultural film may be lowered. On the other hand, when it is large, the solubility of the alkylene oxide added polyhydric alcohol fatty acid ester in water increases. This is because the added polyhydric alcohol fatty acid ester dissolves in the condensed water and flows out, and the antifogging property of the agricultural film may be lowered.

  The nonionic surfactant is contained in at least one of the layers (A), (B) and (C) constituting the agricultural film, preferably in all layers. The content of the nonionic surfactant in each layer is preferably 0.1 to 10 parts by weight, more preferably 1.0 to 5.5 parts per 100 parts by weight of the resin component constituting each layer. Contains 0 part by weight.

  This is because in each layer, if the content of the nonionic surfactant is too small, the antifogging property of the agricultural film becomes insufficient, and the condensed water adhering to the surface of the agricultural film is cultivated in the agricultural house. This is because a so-called “bottom dropping phenomenon” that falls directly on a growing crop is likely to cause disease.

  On the other hand, in each layer, when the content of the nonionic surfactant is too much, the nonionic surfactant bleeds out on the surface of the agricultural film, and the agricultural film becomes sticky. The handleability of the film is reduced.

  In addition, since the nonionic surfactant contained in the agricultural film as described above bleeds out and exudes to the surface of the agricultural film, the agricultural film exhibits excellent antifogging properties. .

[Additive]
The agricultural film may contain a hindered amine light stabilizer, a heat stabilizer, an ultraviolet absorber, a lubricant and the like as long as the physical properties are not impaired as required.

  As the hindered amine light stabilizer, any conventionally known one can be used, and these can be used alone or in admixture of two or more. Specifically, 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]} and the like.

  And as said heat stabilizer, conventionally well-known arbitrary things are used, Specifically, chelators, such as a metal salt of carboxylic acid, a phenolic antioxidant, organic phosphorous acid ester, etc. are mentioned independently Even if it uses, 2 or more types may be used together.

  As the ultraviolet absorber, any conventionally known one can be used. For example, a benzophenone series, a benzotriazole series, a salicylic acid ester series, a cyanoacrylate series or the like can be used alone or in combination of two or more. it can. Specifically, 2,4-dihydroxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2,2′-hydroxy Benzophenone ultraviolet absorbers such as -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-butylphenyl) -5-chlorobe Zotoriazoru, 2- (2'-hydroxy-3 ', 5'-di -tert- amylphenyl) -5-benzotriazole ultraviolet absorbents such as chloro benzotriazole.

  As the lubricant, any conventionally known lubricant may be used, and saturated fatty acid amide such as stearic acid amide, unsaturated fatty acid amide such as erucic acid amide and oleic acid amide, bisamide such as ethylene bis stearic acid amide and the like. May be used alone or in combination of two or more.

  If the thickness of the agricultural film is thin, the mechanical strength of the agricultural film may be reduced. On the other hand, if the thickness is thick, it becomes difficult to cut, bond, and stretch the agricultural film, resulting in poor handling. Therefore, 50-150 micrometers is preferable and 80-120 micrometers is more preferable.

  In the agricultural film, the thickness of the layer (A) is preferably 5 to 30% and more preferably 10 to 20% with respect to the thickness of the entire agricultural film. Moreover, 40-90% is preferable with respect to the thickness of the said whole agricultural film, and, as for the thickness of a layer (B), 60-80% is more preferable. Furthermore, the thickness of the layer (C) is preferably 5 to 30% and more preferably 10 to 20% with respect to the thickness of the whole agricultural film.

  Next, a method for forming the agricultural film will be described. The method for producing the agricultural film is not particularly limited, and examples thereof include conventionally known methods such as a multilayer inflation method, a multilayer T-die method, a multilayer laminate method, and a calendar method.

  Among the above-mentioned film forming methods, after the resin composition comprising the resin component constituting each layer, silica particles and, if necessary, a pigment or the like is melt-kneaded in separate extruders, the resin in a molten state from each extruder The composition is supplied to a circular multilayer die, and a molten resin composition is coextruded from the circular multilayer die to form a cylindrical film, and compressed air is supplied from the center of the circular multilayer die. A multilayer inflation method is preferred in which an agricultural film is formed by stretching a coextruded cylindrical film in the circumferential direction.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

Example 1
1. Preparation of Resin Composition (a) A predetermined amount of linear low density polyethylene (a) shown in Table 1 (density: 0.920 g / cm ³ , melt flow rate: 1.2 g / 10 min), low density Polyethylene (a) (density: 0.920 g / cm ³ , melt flow rate: 1.2 g / 10 min), synthetic silica particle master batch (1) (trade name “PE1300” manufactured by Dainichi Seika Co., Ltd.) Content: 20% by weight, average particle diameter of synthetic silica particles: 8 μm, low density polyethylene content: 80% by weight, low density polyethylene density: 0.919 g / cm ³ , low density polyethylene melt flow rate: 5.0 g / 10 minutes), nonionic surfactant master batch (content of nonionic surfactant: 20% by weight, main component of nonionic surfactant: diglycerin stearate) , Low density polyethylene content: 80% by weight, Low density polyethylene density: 0.920 g / cm ³ , Low density polyethylene melt flow rate: 4.0 g / 10 min), White pigment masterbatch (manufactured by Tokyo Ink Co., Ltd.) Product name “PEX6800”, content of rutile titanium oxide: 60 wt%, average particle size of rutile titanium oxide: 230 nm, low density polyethylene content: 40 wt%, density of low density polyethylene: 0.919 g / cm ^3. Low-density polyethylene melt flow rate: 2.0 g / 10 min) and black pigment masterbatch (trade name “PEX998020” manufactured by Tokyo Ink Co., Ltd.), carbon black content: 40% by weight, low-density polyethylene content: 60% %, the density of the low density polyethylene: 0.919 g / cm ^3, low density polyethylene Merutofu Reito: was 2.0 g / 10 min) resin composition comprising: (a) was prepared.

2. Preparation of Resin Composition (b) A predetermined amount of ethylene-vinyl acetate copolymer (b) shown in Table 1 (vinyl acetate component content: 10% by weight, density: 0.930 g / cm ³ , melt flow rate : 1.0 g / 10 minutes), nonionic surfactant master batch (trade name “S71-D” manufactured by Riken Vitamin Co., Ltd.), content of nonionic surfactant: 20% by weight, nonionic surfactant Main component: diglycerin stearate, content of low density polyethylene: 80% by weight, density of low density polyethylene: 0.920 g / cm ³ , melt flow rate of low density polyethylene: 4.0 g / 10 min), White pigment masterbatch (trade name “PEX6800” manufactured by Tokyo Ink Co., Ltd.), rutile titanium oxide content: 60% by weight, average particle size of rutile titanium oxide: 230 nm, low density Ethylene content: 40 wt%, of low density polyethylene Density: 0.919 g / cm ^3, a low density polyethylene melt flow rate: 2.0 g / 10 min), and a black pigment master batch (Tokyo Ink Co., Ltd. trade name " PEX998020 ”, carbon black content: 40 wt%, low density polyethylene content: 60 wt%, low density polyethylene density: 0.919 g / cm ³ , low density polyethylene melt flow rate: 2.0 g / 10 Min) was prepared.

3. Preparation of resin composition (c) The predetermined amount of linear low density polyethylene (c) shown in Table 1 (density: 0.920 g / cm ³ , melt flow rate: 1.2 g / 10 min), low density Polyethylene (c) (density: 0.920 g / cm ³ , melt flow rate: 1.2 g / 10 min), synthetic silica particle master batch (1) (trade name “PE1300” manufactured by Dainichi Seika Co., Ltd.) Content: 20% by weight, average particle diameter of synthetic silica particles: 8 μm, low density polyethylene content: 80% by weight, low density polyethylene density: 0.919 g / cm ³ , low density polyethylene melt flow rate: 5.0 g / 10 minutes), nonionic surfactant master batch (content of nonionic surfactant: 20% by weight, main component of nonionic surfactant: diglycerin stearate) Content of low density polyethylene: 80% by weight, density of low density polyethylene: 0.920 g / cm ³ , melt flow rate of low density polyethylene: 4.0 g / 10 min), and a predetermined amount of white pigment masterbatch ( Product name “PEX6800” manufactured by Tokyo Ink Co., Ltd. Content of rutile titanium oxide: 60% by weight, average particle size of rutile titanium oxide: 230 nm, content of low density polyethylene: 40% by weight, density of low density polyethylene: A resin composition (c) consisting of 0.919 g / cm ³ and low density polyethylene melt flow rate: 2.0 g / 10 min) was prepared.

4). Film formation for agricultural use A multilayer film forming apparatus is prepared by connecting the tip of three extruders for layer (A), layer (B), and layer (C) to the same circular multilayer die. In the multilayer film forming apparatus, the resin composition (a) is used for the layer (A) extruder, the resin composition (b) is used for the layer (B) extruder, and the layer (C) extruder is used. After the resin composition (c) is supplied and melt-kneaded in the above three extruders, the molten resin composition is supplied from each extruder to a circular multilayer die and melted from the circular multilayer die. The resin composition in a state is co-extruded to form a layer (A), layer (B), and layer (C) that are laminated and integrated in this order, and compressed from the center of a circular multilayer die. After supplying air and stretching the coextruded cylindrical film in the circumferential direction, the cylindrical film is cooled by cooling air, An agricultural film having an overall thickness of 100 μm and a thickness ratio of each layer (layer (A) / layer (B) / layer (C)) of 1/3/1 is produced by cutting and winding the cylindrical film. Filmed.

(Examples 2-3 and Comparative Examples 1-2)
As shown in Tables 1 and 2, an agricultural film was formed in the same manner as in Example 1 except that the composition of each resin composition was changed. The ethylene-vinyl acetate copolymer (a), the synthetic silica particle master batch (2), the synthetic silica particle master batch (3), and the lubricant described in Tables 1 and 2 were as follows.

Ethylene-vinyl acetate copolymer (a): vinyl acetate component content 5% by weight, density 0.928 g / cm ³ , melt flow rate 1.0 g / 10 min.
Synthetic silica particle master batch (2): Prime polymer product name “BB36”, synthetic silica particle content 15 wt%, synthetic silica particle average particle diameter 6 μm, low density polyethylene content 85 wt%, low density polyethylene density 0.923 g / cm ³ , low density polyethylene melt flow rate 0.7 g / 10 min.
Synthetic silica particle master batch (3): Prime polymer product name “BB37”, synthetic silica particle content 15 wt%, synthetic silica particle average particle diameter 4 μm, low density polyethylene content 85 wt%, low density polyethylene density 0.923 g / cm ³ , low density polyethylene melt flow rate 0.7 g / 10 min.
Lubricant: oleic acid amide, trade name “M105” manufactured by Ube Maruzen Polyethylene Co., Ltd.

  Next, the mechanical strength, heat-fusibility, peelability and whiteness of the layer (C) of the agricultural film obtained as described above were evaluated in the following manner, and the results are shown in Tables 1 and 2. Indicated. In addition, the numerical value in the parenthesis in the column of “Synthetic silica particle content” in the resin compositions (a), (b) and (c) in Table 1 and Table 2 is contained in each resin composition. The content (parts by weight) of the synthetic silica particles when the total amount of the resin components is converted to 100 parts by weight is shown. Moreover, the numerical value in the parenthesis in the column of “nonionic surfactant content” of the resin compositions (a), (b) and (c) in Tables 1 and 2 is included in each resin composition. It shows the content (parts by weight) of the nonionic surfactant when the total amount of the resin components used is converted to 100 parts by weight. Furthermore, the numerical values in parentheses in the columns of “white pigment content” and “black pigment content” in the resin compositions (a), (b) and (c) in Tables 1 and 2 are the values for each resin composition. The white pigment content (parts by weight) or the black pigment content (parts by weight) when the total amount of resin components contained therein is converted to 100 parts by weight is shown.

(Mechanical strength)
The tensile breaking point load of the agricultural film produced above was measured according to JIS K 6781 using a strograph (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the mechanical strength of the agricultural film was determined based on the following criteria. evaluated.
(Circle): The breaking point load was 3000 g or more.
(Triangle | delta): The breaking point load was 1000 g or more and less than 3000 g.
X: The load at break was less than 1000 g.

(Heat resistance)
The agricultural film 50 cm produced above was wound around an iron core having a diameter of 2 cm to form a roll, and this roll was stored in an oven at 80 ° C. and a relative humidity of 30% RH for 24 hours. After storage, the film was unwound from the roll and evaluated whether the films were fused together based on the following criteria.
A: Not fused.
○: Adhesion has not occurred but is in close contact.
Δ: No fusion occurred, but white when peeled. ×: Fusion occurred.

(Peelability)
The agricultural film produced above is cut to a size of 10 cm ² , and the two films obtained are stacked and stored with a 20 kg load at 40 ° C. for 48 hours, after which the overlapping films are easy to peel off. Was evaluated based on the following criteria.
○: Easy to peel off.
(Triangle | delta): Although it peels, it is hard to peel off.
X: Not peeled off.

(White gloss of layer (C))
Glossiness was measured in accordance with JIS-Z8741 using a variable gloss meter (UVG-5D digital variable gloss meter manufactured by Suga Test Instruments Co., Ltd.) for the obtained agricultural film layer (C). The white gloss of the agricultural film layer (C) was evaluated based on the following criteria at an angle of 60 degrees.
○: 45 or more Δ: 20 or more and less than 45 ×: less than 20

Claims (5)

A polyethylene resin having a density of 0.900 to 0.930 g / cm ³ and a melt flow rate (MFR) of 0.3 to 5.0 g / 10 min, or a vinyl acetate content of 5.0 to 25% by weight And a layer (A) comprising an ethylene-vinyl acetate copolymer having a melt flow rate (MFR) of 0.5 to 4.0 g / 10 min,
A layer (B) comprising an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5.0 to 25% by weight and a melt flow rate (MFR) of 0.5 to 4.0 g / 10 min, and a density of A layer (C) containing a polyethylene resin having 0.900 to 0.930 g / cm ³ and a melt flow rate (MFR) of 0.3 to 5.0 g / 10 minutes is laminated and integrated in this order. Become
At least one of the layer (A) and the layer (C) contains 0.1 to 0.5 silica particles having an average particle diameter of 5 to 10 μm with respect to 100 parts by weight of the resin component contained in each layer. An agricultural film characterized by containing a weight part. The layer (A) comprises a polyethylene resin having a density of 0.900 to 0.930 g / cm ³ and a melt flow rate (MFR) of 0.3 to 5.0 g / 10 min. Item 2. The agricultural film according to Item 1.   The layer (A) contains 0.1 to 0.5 parts by weight of silica particles having an average particle diameter of 5 to 10 μm with respect to 100 parts by weight of the resin component, and the layer (B) does not contain silica particles. The agricultural film according to claim 1, wherein:   The layer (A) and the layer (C) contain 0.1 to 0.5 part by weight of silica particles having an average particle diameter of 5 to 10 μm with respect to 100 parts by weight of the resin component contained in each layer, and the layer The agricultural film according to claim 1 or 2, wherein (B) does not contain silica particles. The layer (A) contains 5.0 to 30 parts by weight of a white pigment and 0.1 to 5.0 parts by weight of a black pigment with respect to 100 parts by weight of the resin component.
The layer (B) contains 1.0 to 10 parts by weight of a white pigment and 0.1 to 5.0 parts by weight of a black pigment with respect to 100 parts by weight of the resin component, and the layer (C) contains 100 parts by weight of the resin component. The agricultural film according to any one of claims 1 to 4, comprising 5.0 to 30 parts by weight of a white pigment and no black pigment with respect to parts by weight.