JP2019017360A - Agricultural film - Google Patents

Abstract

To provide an agricultural film capable of switching between thermal insulation and ventilation according to the state of ambient temperature.SOLUTION: An agricultural film 1 is made up of a belt-like film and used by stretching so as to cover an internal space, in which a plurality of small holes 2 having a diameter of 0.1 mm or more and 4.0 mm or less are formed on the entire surface of the belt-like film, and provided such that an opening ratio by the small holes 2 becomes 0.5 to 1.5% with respect to a film total area. In the case where the temperature of air inside the internal space is heated by heat of sunlight incident from outside the film and is higher than air outside the film by 10°C or more, upward flow of heated air directed from downward to upward in the internal space is generated, air inside the internal space is discharged from the internal space to the outside of the film via the small holes 2, and rise of air inside the internal space temperature is suppressed. In the case where heating by heat of sunlight incident from the film is small and a temperature difference between air inside the internal space and air outside the film is less than 10°C, inflow of air outside the film into the internal space is suppressed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an agricultural film, and more particularly to an agricultural film capable of switching between heat retention and ventilation according to the outside air temperature.

  Agricultural films coated on houses and tunnels are used to improve the growth environment of crops.

  One of the performances required for agricultural films is heat retention and temperature rise. When the outside air temperature is low, the growth of crops is delayed or it is easy to cause cold damage. Therefore, it is important that the agricultural film exhibits heat retention and temperature rise.

On the other hand, ventilation in agricultural films is also important in order to prevent the temperature inside the film from rising too high.
Generally, it is ventilated by winding up both sides of the film, but it takes manpower. An agricultural film in which a plurality of small holes are provided in the film has been developed for the purpose of ventilation (Patent Document 1). However, such a film has a problem that it is difficult to obtain heat retention and temperature rise because air always flows in and out through the small holes.

JP 2006-340647 A

  In view of the conventional problems as described above, when the outside air temperature is low, the present inventor suppresses the inflow and outflow of air between the inside and outside of the film, and exhibits heat retention and temperature rise. We have developed an agricultural film that can control the excessive temperature rise inside the film by flowing out the warm air inside the film outside the film when the temperature is high and the temperature inside the film is raised.

  Then, the subject of this invention is providing the agricultural film which can switch a heat retention and ventilation according to the condition of external temperature.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

(Claim 1)
Agricultural film consisting of a strip-shaped film and used to extend and cover the internal space.
A plurality of small holes having a diameter of 0.1 mm or more and 4.0 mm or less are formed on the entire surface of the belt-like film, and the aperture ratio due to the small holes is 0.5 to 1.5% with respect to the total area of the film. Provided in
When the temperature of the air in the internal space is heated by the heat of sunlight incident from the outside of the film and is 10 ° C. or more higher than the air outside the film, the heated air is directed upward from below in the internal space. The upward flow is generated, and through the small holes, the air in the internal space is discharged from the internal space to the outside of the film, and the air temperature in the internal space is suppressed from rising.
When the temperature difference between the air in the internal space and the air outside the film is less than 10 ° C., the air outside the film flows into the internal space. An agricultural film characterized by having a structure that suppresses the above.
(Claim 2)
When the air in the internal space is heated by the heat of sunlight incident from the outside of the film, and the air temperature in the internal space is suppressed by 10 ° C. or higher than the air outside the film,
The agricultural use according to claim 1, wherein the fluid pressure of the upward flow of air is defined so as to be equal to or greater than the pressure loss of the small hole by the cross-sectional area based on the opening ratio of the small hole. the film.
(Claim 3)
When the temperature difference between the air in the internal space and the air outside the film is less than 10 ° C., the air outside the film flows into the internal space. The configuration that suppresses the
The agriculture according to claim 1 or 2, wherein the air flow in the internal space is substantially limited, and an air pocket is formed that exhibits a heat insulation effect without flowing in the small hole. Film.
(Claim 4)
Agricultural film consisting of a strip-shaped film and used to extend and cover the internal space.
A plurality of slit holes having a length of 5 mm or more and 15 mm or less and a width of 0.1 mm or more and 0.8 mm or less are formed on the entire surface of the belt-shaped film, and the opening ratio by the slit holes is 0.5 to Provided to be 1.5%,
When the temperature of the air in the internal space is heated by the heat of sunlight incident from the outside of the film and is 10 ° C. or more higher than the air outside the film, the heated air is directed upward from below in the internal space. The upward flow is generated, and through the slit hole, the air in the internal space is discharged from the internal space to the outside of the film, and the rise of the air temperature in the internal space is suppressed.
When the temperature difference between the air in the internal space and the air outside the film is less than 10 ° C., the air outside the film flows into the internal space. An agricultural film characterized by having a structure that suppresses the above.
(Claim 5)
When the air in the internal space is heated by the heat of sunlight incident from the outside of the film, and the air temperature in the internal space is suppressed by 10 ° C. or higher than the air outside the film,
The agricultural use according to claim 4, wherein the fluid pressure of the upward flow of air is defined to be equal to or higher than the pressure loss of the slit hole by a cross-sectional area based on the opening ratio of the slit hole. the film.
(Claim 6)
When the temperature difference between the air in the internal space and the air outside the film is less than 10 ° C., the air outside the film flows into the internal space. The configuration that suppresses the
The agriculture according to claim 4 or 5, wherein a flow of air in the internal space is substantially restricted so that an air pocket is formed which exhibits a heat insulation effect without flowing in the slit hole. Film.
(Claim 7)
The agricultural film according to any one of claims 4 to 6, wherein the slit hole is formed by arranging a plurality of slit holes radially to form a slit group.

  ADVANTAGE OF THE INVENTION According to this invention, the effect which can provide the agricultural film which can switch a heat retention and ventilation according to the condition of external temperature is acquired.

The figure which shows an example of the film for agriculture which concerns on this invention The figure which illustrates notionally the mechanism of embodiment of this invention The figure which shows the other example of the film for agriculture which concerns on this invention The figure explaining the example of composition of a slit group

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an example of an agricultural film according to the present invention.
In the figure, 1 is a strip-shaped agricultural film (hereinafter sometimes referred to simply as a film), and 2 is a small hole formed on the entire surface of the film.

  The agricultural film 1 is used by forming a house skeleton such as an arch pipe in a farm field or the like where crop cultivation is performed, and extending so as to cover an internal space formed by the house skeleton.

  In this embodiment, small holes having a diameter of 0.1 mm or more and 4.0 mm or less are provided with an opening ratio of 0.5 to 1.5% with respect to the entire film. When the aperture ratio is Ar, the area of one small hole is s with respect to the total area S of the film, and n is the number of small holes formed on the entire surface of the film, Ar = (s × n) / S It is represented by When expressed as a percentage, Ar is multiplied by 100.

  In the present embodiment, due to the film configuration described above, when the air in the internal space is heated by the heat of sunlight incident from the outside of the film and is 10 ° C. higher than the air outside the film, An upward flow of heated air is generated from the top upward. Then, the air in the internal space is discharged from the internal space to the outside of the film through the small hole 2. By doing so, an increase in the air temperature in the internal space is suppressed.

  Also, when the temperature difference between the air in the internal space and the air outside the film is less than 10 ° C. due to little heating by sunlight incident from the film, the air outside the film enters the internal space. Suppresses inflow. That is, it is possible to switch between heat retention and ventilation according to the outside air temperature.

The mechanism of the present embodiment will be conceptually described based on FIG.
FIG. 2A is a schematic film cross-sectional view when the temperature difference between the inside and outside of the film is less than 10 ° C., and FIG. 2B shows the case where the temperature difference between the inside and outside of the film is 10 ° C. or more. It is a film schematic sectional drawing.

<When the temperature difference between the inside and outside of the film is less than 10 ° C.>
As shown in FIG. 2A, energy loss (energy loss per unit volume) due to flow path resistance when outside air enters and exits in the small holes 2 provided in the film 1 is denoted by ΔP ₁ . The film inside, air and convection, to the kinetic energy of the air at this time is E _1.

In a situation where the temperature difference between the inside and outside of the film is less than 10 ° C., the relationship of E ₁ <ΔP ₁ is established from the definition of the diameter of the small holes and the opening ratio, so that it is difficult for air to flow out from the inside to the outside. In such a state, the heat retaining property and temperature rising property by the film are exhibited.

<When the temperature difference between the inside and outside of the film is 10 ° C. or more>
Next, for example, when the temperature difference between the inside and outside of the film is 10 ° C. or more due to an increase in the outside air temperature, the air inside the film is warmed and the density of the inside air becomes small. Inside the film, an upward airflow of air from the bottom to the top is created. As a result, the kinetic energy of the air inside the film is increased, and the kinetic energy E _{2 of the} air is E ₂ > E ₁ as shown in FIG.

Furthermore, when the temperature inside the film rises, the energy loss ΔP ₂ due to the flow path resistance in this case becomes smaller than when the temperature difference between the inside and outside of the film is less than 10 ° C. This is because the diameter of the small hole substantially increases due to thermal expansion.

As a result, as shown in FIG. 2B, when the temperature difference between the inside and outside of the film is 10 ° C. or more, the relationship of E ₂ > ΔP ₂ is established, and the air inside the film flows out from the small holes. Ventilation inside the film will be realized.

  Although the heat conduction of the film itself exists theoretically, it is not necessary to consider it because the boundary resistance of the film surface is large. This is because it is sufficient to consider the heat transfer of air passing through the small holes.

  When the small hole is circular, the diameter is 0.1 mm or more and 4.0 mm or less, preferably 0.5 mm or more and 3.5 mm or less, and particularly preferably 1.0 mm or more and 3.0 mm or less.

  If the diameter is smaller than 0.1 mm, it is difficult to obtain the effect of switching between heat retention and ventilation depending on the outside air temperature, it becomes difficult to process, and if it is larger than 4.0 mm, there is a problem in heat retention, which is not preferable.

  The small holes may be elliptical holes or polygonal holes (for example, triangular holes, quadrangular holes, pentagonal holes, star-shaped holes, etc.) other than round holes.

  In this embodiment, the diameter of the small hole means the diameter when the small hole is a round hole, and in the case of a polygonal hole other than the round hole, the diameter in terms of a circle calculated from the area of the polygonal hole is used. means.

  In the present invention, the aperture ratio is 0.5 to 1.5%, preferably 0.7 to 1.3%.

If the opening ratio is less than 0.5%, the flow resistance when air flows in and out from the small holes becomes large, so that the air flow becomes difficult and ventilation becomes difficult.
When the opening ratio exceeds 1.5%, air always flows in and out, so that it is difficult to keep warm at low temperatures.

  The method for forming the small holes 2 is not particularly limited, and examples thereof include a method of forming the film 1 by punching, puncturing, or melting with a heated needle, laser processing, and the like. From the viewpoint, a method of puncturing or melting with a heated needle or the like, or laser processing is preferably employed.

In the film 1, the small holes 2 to be formed have a very small diameter as described above. However, since the film 1 is open even if it has a small diameter, it is considered that the inflow and outflow of air always occurs normally. It is done.
However, by forming the small holes 2 with the size and opening ratio of the present invention, when the outside air is at a low temperature, the air flow between the inside and outside of the film is suppressed, and the inside of the film is kept warm, When the outside air is hot and the temperature inside the film rises, the temperature inside the film can be suppressed by letting warm air flow out from the inside of the film.

  The film 1 is not particularly limited as long as it is a resin film. For example, the film 1 is made of various impermeable thermoplastic synthetic resins such as a vinyl chloride resin film, a polyolefin resin film such as polyethylene and ethylene-vinyl acetate copolymer. The film can be used.

  Of these, polyolefin resins are preferred in the present invention. Examples of polyolefin resins include α-olefin homopolymers and copolymers with heterogeneous monomers based on α-olefins, such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene 1 Copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, ethylene-α-olefin copolymer such as ethylene-decene copolymer, ethylene- Examples thereof include a vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-methyl methacrylate copolymer, an ethylene-vinyl acetate-methyl methacrylate copolymer, and an ionomer copolymer. These resins can be used alone or in a blend.

  The thickness of the film 1 can be 20-200 micrometers. In particular, when the film 1 is made of a low density polyethylene resin, it is preferably 30 to 150 μm, more preferably 50 to 100 μm in consideration of cost, strength, flexibility, workability and the like.

  If the thickness is less than 30 μm, the durability tends to be lowered, and if it exceeds 150 μm, the flow resistance increases, so that it is difficult for air to flow out.

  Since the film 1 has the small holes 2, the infiltration of rainwater occurs. At this time, a hydrophilic film may be provided on one side or both sides of the film 1 so as to cover at least a part of the small holes 2 in order to suppress crop diseases caused by dropping of rainwater.

  The hydrophilic film can be formed by applying a hydrophilic coating liquid mainly composed of an inorganic hydrophilic colloid substance and a hydrophilic organic compound.

Examples of inorganic hydrophilic colloid materials include colloidal silica, colloidal alumina, colloidal Fe (OH) ₂ , colloidal Sn (OH) ₄ , colloidal TiO ₂ , colloidal BaSO ₄ and colloidal lithium A silicate etc. can be mentioned.

  Examples of the hydrophilic organic compound include various surfactants (nonionic, anionic and cationic) and hydroxyl group-containing vinyl monomer components as main components, and acid group-containing vinyl monomer components of 0.1 to 0.1%. Examples thereof include a copolymer containing 40%, or a partially or completely neutralized product thereof, and a sulfonic acid group-containing polyester resin.

  In addition, other components such as an ultraviolet absorber, a colorant, an agrochemical, and a fertilizer can be blended in the hydrophilic coating solution for forming the hydrophilic film as long as the effect of the hydrophilic film is not hindered.

  The hydrophilic coating solution may be applied so as to cover at least a part of the small holes of the film 1, or may be applied to one or both sides of the film 1. At this time, it is possible to apply even inside the small hole from the viewpoint of more effectively moving rainwater.

  Examples of the method for applying the hydrophilic coating solution include spray coating, brush coating, roll coating and the like.

  The hydrophilic film may be formed by repeatedly applying a new aqueous coating solution a plurality of times.

  Various additives can be added to the film 1 as necessary. Specific examples include inorganic fillers (calcium carbonate, various hydrotalcite compounds, talc, silica, alumina, zeolite, and the like), lubricants, antiblocking agents, drop-free agents, and the like.

  In the above description, the film may be a film for house exterior, a film for tunnel exterior, or a curtain.

  In the present invention, a slit hole may be used instead of the small hole. Even when slit holes are used, a plurality of slit holes are formed on the entire surface of the belt-like film. This will be described with reference to FIGS.

  FIG. 3 is a view showing another example of the agricultural film according to the present invention. The film 1 is provided with slit holes 2 ′ instead of the small holes 2.

  The slit hole 2 'has a length of 5 mm to 15 mm, preferably 7 mm to 12 mm. The slit hole has a width of 0.1 mm to 0.8 mm, preferably 0.2 mm to 0.4 mm.

  Since the slit hole 2 'has the above length and width, the same function as the small hole 2 having the specific diameter described above is exhibited. Even when the slit hole 2 ′ is used, the slit hole 2 ′ is provided so that the aperture ratio is 0.5 to 1.5% with respect to the entire film area.

  In the case of the slit hole 2 ′, it is preferable to configure a slit group by arranging a plurality of slit holes radially.

  Hereinafter, a configuration example of the slit group will be described with reference to FIG.

  4A and 4B are diagrams for explaining a configuration example of the slit group. FIG. 3A is an example of the slit group constituted by five slit holes, and FIG. 3B is constituted by six slit groups. One example of each slit group is shown.

  The slit group 20 shown in FIG. 4A is composed of five straight slit holes 2 ′. At this time, the five slit holes 2 ′ are radially arranged at equal angles so that a virtual straight line connecting the outer end portions preferably forms a regular pentagon. Each slit hole 2 'is arranged at a distance from the central portion C of radiation (indicated by a one-dot chain line in FIG. 4). In the following description, the slit group 20 is also referred to as a pentagon if necessary.

  The slit hole 2 'opens with a predetermined opening area. That is, the slit hole 2 ′ has an opening area in a state where it is placed flat, unlike a simple cut. Therefore, the aperture ratio defined by the present invention can be achieved. Such a slit hole 2 can be suitably formed by laser processing.

  The opening shape of the slit hole 2 ′ is rectangular when enlarged, and the opening area is represented by the product of length and width.

  The slit group 20 shown in FIG. 4B is composed of six straight slit holes 2 ′. At this time, the six slit holes 2 ′ are radially arranged at equal angles so that a virtual straight line connecting the outer end portions preferably forms a regular hexagon. Each slit hole 2 'is arranged at a distance from the central portion C of the radiation. In the following description, the slit group 20 is also referred to as a hexagon as necessary.

  The structure of a slit group is not limited to said example, It can be set as various forms. For example, further slit holes may be formed outside the plurality of slits constituting the slit group described above or between the plurality of slits to form the slit group.

  In the slit group described above, the number of slit holes constituting the slit group and the number of slit groups provided on the film 1 can be set so as to achieve the aperture ratio defined by the present invention. it can.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

1. Film production (film 1)
A commercially available film material for agriculture (made of polyethylene resin; “Mikado Longevity”) was provided with small holes (round holes) having a diameter of 3 mm so as to have an opening ratio of 1% by melt cutting.

  Next, a coating solution prepared as described below was applied to the entire surface of one side of the film (the side that becomes the outer surface of the tunnel when spread in a tunnel). The obtained film was designated as film 1.

<Coating solution>
A stock solution consisting of 15% by weight of colloidal silica and 1% by weight of a surfactant is diluted 100 times with water and used.

(Film 2)
In the film 1, a film 2 was obtained in the same manner as the film 1 except that a slit hole having a length of 10 mm and a width of 0.31 mm was formed instead of the round hole.
Here, as in the case shown in FIG. 4A, a slit group (pentagon) is formed by five slit holes arranged radially. A plurality of such slit groups were formed on the entire film so as to have an aperture ratio of 1%.

(Film 3)
In the film 2, the film 3 was obtained in the same manner as the film 2 except that the slit group (hexagon) was constituted by six slit holes in the same manner as shown in FIG. As the number of slit holes constituting the slit group was increased from 5 to 6 in comparison with the film 2, the aperture ratio was changed from 1% to 1.2%.

(Film 4)
A film 4 was obtained in the same manner as the film 1 except that the opening ratio in the film 1 was changed to 2%.

(Film 5)
A film 5 was obtained in the same manner as the film 1 except that the small holes were omitted from the film 1.

2. Film extension and film-covered internal environment test Films 1 to 5 were respectively spread on a tunnel frame to obtain agricultural tunnels 1 to 5.

  For each of the agricultural tunnels 1 to 5, the minimum temperature and maximum temperature inside the tunnel and the minimum temperature and maximum temperature of the outside air temperature in one day were measured. The results are shown in Tables 1 and 2.

(1) Test date: March 15 (clear)

(2) Test date: March 16 (cloudy)

<Evaluation>
When the temperature is high, the tunnel 4 having an opening ratio of 2% can suitably control the temperature rise by ventilating the inside of the film coating (Table 1). However, since air always flows in and out from the opening portion, It is almost impossible to obtain the temperature raising effect (Table 2).

  The tunnel 5 having an opening rate of 0% suitably exhibits a temperature rising effect because it seals the inside of the film (Table 2). On the other hand, since there is no air inflow / outflow, when the outside temperature rises, The temperature rises too much (Table 1).

  On the other hand, in tunnels 1 to 3 with an aperture ratio of 1%, while obtaining the same temperature increase effect as tunnel 5 with an aperture ratio of 0% (Table 2), (Table 1).

  This is because the opening ratio of the films 1 to 3 used for the tunnels 1 to 3 is within the range of the present invention, so that the insulation and ventilation can be switched depending on the outside air temperature. This effect can be switched when the temperature difference between the inside of the film coating and the outside of the film coating is about 10 ° C.

  When the air inside the film coating is heated by 10 ° C. or more higher than the air outside the film coating, the small holes and slit holes allow the heated air inside the film coating to be transferred from the inside of the film coating to the outside of the film coating. It becomes the discharge part to discharge to.

  Further, when the temperature difference is less than 10 ° C., the small holes and the slit holes do not discharge the air inside the film coating from the inside of the film coating to the outside of the film coating.

1: Agricultural film 2: Small hole 2 ': Slit hole 20: Slit group

Claims (7)

Agricultural film consisting of a strip-shaped film and used to extend and cover the internal space.
A plurality of small holes having a diameter of 0.1 mm or more and 4.0 mm or less are formed on the entire surface of the belt-like film, and the aperture ratio due to the small holes is 0.5 to 1.5% with respect to the total area of the film. Provided in
When the temperature of the air in the internal space is heated by the heat of sunlight incident from the outside of the film and is 10 ° C. or more higher than the air outside the film, the heated air is directed upward from below in the internal space. The upward flow is generated, and through the small holes, the air in the internal space is discharged from the internal space to the outside of the film, and the air temperature in the internal space is suppressed from rising.
When the temperature difference between the air in the internal space and the air outside the film is less than 10 ° C., the air outside the film flows into the internal space. An agricultural film characterized by having a structure that suppresses the above. When the air in the internal space is heated by the heat of sunlight incident from the outside of the film, and the air temperature in the internal space is suppressed by 10 ° C. or higher than the air outside the film,
The agricultural use according to claim 1, wherein the fluid pressure of the upward flow of air is defined so as to be equal to or greater than the pressure loss of the small hole by the cross-sectional area based on the opening ratio of the small hole. the film. When the temperature difference between the air in the internal space and the air outside the film is less than 10 ° C., the air outside the film flows into the internal space. The configuration that suppresses the
The agriculture according to claim 1 or 2, wherein the air flow in the internal space is substantially limited, and an air pocket is formed that exhibits a heat insulation effect without flowing in the small hole. Film. Agricultural film consisting of a strip-shaped film and used to extend and cover the internal space.
A plurality of slit holes having a length of 5 mm or more and 15 mm or less and a width of 0.1 mm or more and 0.8 mm or less are formed on the entire surface of the belt-shaped film, and the opening ratio by the slit holes is 0.5 to Provided to be 1.5%,
When the temperature of the air in the internal space is heated by the heat of sunlight incident from the outside of the film and is 10 ° C. or more higher than the air outside the film, the heated air is directed upward from below in the internal space. The upward flow is generated, and through the slit hole, the air in the internal space is discharged from the internal space to the outside of the film, and the rise of the air temperature in the internal space is suppressed.
When the temperature difference between the air in the internal space and the air outside the film is less than 10 ° C., the air outside the film flows into the internal space. An agricultural film characterized by having a structure that suppresses the above. When the air in the internal space is heated by the heat of sunlight incident from the outside of the film, and the air temperature in the internal space is suppressed by 10 ° C. or higher than the air outside the film,
The agricultural use according to claim 4, wherein the fluid pressure of the upward flow of air is defined to be equal to or higher than the pressure loss of the slit hole by a cross-sectional area based on the opening ratio of the slit hole. the film. When the temperature difference between the air in the internal space and the air outside the film is less than 10 ° C., the air outside the film flows into the internal space. The configuration that suppresses the
The agriculture according to claim 4 or 5, wherein a flow of air in the internal space is substantially restricted so that an air pocket is formed which exhibits a heat insulation effect without flowing in the slit hole. Film.   The agricultural film according to any one of claims 4 to 6, wherein the slit hole is formed by arranging a plurality of slit holes radially to form a slit group.

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