JP6726647B2 - Agricultural film - Google Patents

Description

TECHNICAL FIELD The present invention relates to an agricultural film, and more particularly, to an agricultural film capable of switching between heat retention and ventilation depending on the ambient temperature.

The agricultural film coated on the house or tunnel is used for improving the growth environment of agricultural products.

One of the performances required of agricultural films is heat retention and temperature rise. When the outside air temperature is low, the growth of agricultural products is delayed and cold damage is likely to occur. Therefore, it is important for the agricultural film to exhibit heat retaining properties and temperature rising properties.

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

JP 2006-340647 A

In view of the conventional problems as described above, the present inventor, when the outside air temperature is low, the inflow and outflow of air between the inside and the outside of the film is suppressed, and the heat retaining property and the temperature raising property are exhibited, and the outside We have developed an agricultural film that can suppress excessive temperature rise inside the film by letting out the warm air inside the film to the outside when the temperature is high and the temperature inside the film rises.

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

Other problems of the present invention will be clarified by the following description.

The above problems can be solved by the following inventions.

(Claim 1)
Agricultural film that consists of a strip-shaped film and is spread to 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 band-shaped film, and the aperture ratio by the small holes is 0.5 to 1.5% with respect to the entire area of the film. Is 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 higher than the air outside the film by 10° C. or more, the heated air is directed from the lower side to the upper side in the internal space. Is generated, the air in the internal space is discharged from the internal space to the outside of the film through the small holes, and the temperature of the internal space is suppressed from increasing.
When the temperature of the air in the internal space and the air outside the film is less than 10° C. due to little heating by the heat of sunlight incident from the film, the air outside the film flows into the internal space. An agricultural film having a structure for suppressing the occurrence of
(Claim 2)
When the air in the internal space is heated by the heat of sunlight incident from the outside of the film and is higher than the air outside the film by 10° C. or more, a configuration that suppresses an increase in the temperature of the air in the internal space,
The agricultural product according to claim 1, wherein the cross-sectional area based on the aperture ratio regulation of the small holes is defined such that the fluid pressure of the upward flow of air is equal to or higher than the pressure loss of the small holes. the film.
(Claim 3)
When the temperature of the air in the internal space and the air outside the film is less than 10° C. due to little heating by the heat of sunlight incident from the film, the air outside the film flows into the internal space. The configuration that suppresses
The agriculture according to claim 1 or 2, wherein the flow of air in the internal space is substantially limited to form an air pool that exhibits adiabatic action without flowing in the small holes. Film.
(Claim 4)
Agricultural film that consists of a strip-shaped film and is spread to 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 band-shaped film, and the aperture ratio by the slit holes is 0.5 to the entire area of the film. It is set 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 higher than the air outside the film by 10° C. or more, the heated air is directed from the lower side to the upper side in the internal space. Is generated, the air in the internal space is discharged from the internal space to the outside of the film through the slit hole, and has a configuration of suppressing an increase in the air temperature of the internal space,
When the temperature of the air in the internal space and the air outside the film is less than 10° C. due to little heating by the heat of sunlight incident from the film, the air outside the film flows into the internal space. An agricultural film having a structure for suppressing the occurrence of
(Claim 5)
When the air in the internal space is heated by the heat of sunlight incident from the outside of the film and is higher than the air outside the film by 10° C. or more, a configuration that suppresses an increase in the temperature of the air in the internal space,
5. The agricultural use according to claim 4, wherein the cross-sectional area based on the aperture ratio regulation of the slit hole is regulated so that the fluid pressure of the upward flow of air is equal to or more than the pressure loss of the slit hole. the film.
(Claim 6)
When the temperature of the air in the internal space and the air outside the film is less than 10° C. due to little heating by the heat of sunlight incident from the film, the air outside the film flows into the internal space. The configuration that suppresses
The agriculture according to claim 4 or 5, wherein the air flow in the internal space is substantially limited to form an air reservoir that exhibits a heat insulating effect without flowing in the slit holes. Film.
(Claim 7)
The agricultural film according to any one of claims 4 to 6, wherein the slit holes are 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 heat retention and ventilation according to the condition of outside temperature is acquired.

The figure which shows an example of the film for agriculture which concerns on this invention. The figure which explains notionally the mechanism of the execution form of this invention The figure which shows the other example of the agricultural film which concerns on this invention. The figure explaining the structural example of a slit group.

Hereinafter, modes 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 simply referred to 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 field where crops are cultivated, and by spreading the film so as to cover the 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 aperture ratio of 0.5 to 1.5% with respect to the entire film. If the aperture ratio is Ar and the area of one small hole is s with respect to the total area S of the film, and the number of small holes formed on the entire surface of the film is n, then Ar=(s×n)/S It is represented by. When expressed in percentage, Ar is multiplied by 100.

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

Further, when the temperature of the air in the inner space and the air outside the film is less than 10° C. due to little heating by the heat of the sunlight incident from the film, the air outside the film is not contained in the inner space. Suppress inflow. That is, it is possible to switch between heat retention and ventilation depending on the condition of the outside temperature.

The mechanism of the present embodiment will be conceptually described with reference to FIG.
2(a) 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. 2(b) is when the temperature difference between the inside and outside of the film is 10° C. or more. FIG. 3 is a schematic sectional view of a film.

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

In the 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 air is unlikely to flow out from the inside of the film to the outside. In such a state, the film retains heat and heat.

<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 the outside of the film is 10° C. or more due to the rise of the outside air temperature, the air inside the film is warmed and the density of the inside air is reduced. Inside the film, an updraft of air from the bottom to the top is created. As a result, the kinetic energy of the air inside the film increases, and the kinetic energy E _{2 of the} air becomes E ₂ >E ₁ as shown in FIG.

Further, 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 holes is substantially increased by the thermal expansion.

As a result, as shown in FIG. 2B, when the temperature difference between the inside and the 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 comes to be realized.

Although the heat conduction of the film itself theoretically exists, it does not need to be considered 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 holes are circular, the diameter thereof 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 becomes difficult to obtain the effect of switching between heat retention and ventilation depending on the condition of the outside temperature, and 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 oval holes or polygonal holes (for example, triangular holes, quadrangular holes, pentagonal holes, star-shaped holes, etc.) other than round holes.

In the present embodiment, the diameter of the small hole means the diameter of the small hole when the hole is a round hole, and in the case of a polygonal hole other than the round hole, the circle-converted diameter obtained from the area of the polygonal hole. 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 path resistance when air flows in and out through the small holes becomes large, so that the air flow becomes difficult and the ventilation becomes difficult.
When the opening ratio exceeds 1.5%, air always flows in and out, and it becomes difficult to keep the temperature low.

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

Although the small holes 2 formed in the film 1 have a very small diameter as described above, even if the small holes 2 have a small diameter, they are open, so that it is considered that air usually flows in and out at all times. To be
However, when the outside air is at a low temperature by forming the small holes 2 with the diameter and opening ratio of the present invention, the flow of air between the inside and outside of the film is suppressed to keep the inside of the film warm, When the temperature of the inside of the film rises due to the high temperature of the outside air, the warmed air can flow out from the inside of the film to the outside of the film to suppress the rise in the inside of the film.

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

Of these, polyolefin resins are preferable in the present invention. The polyolefin resin is a homopolymer of α-olefin or a copolymer with a different type of monomer whose main component is α-olefin, such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene 1 Ethylene-α-olefin copolymers such as copolymers, ethylene-4-methyl-1-pentene copolymers, ethylene-hexene copolymers, ethylene-octene copolymers, ethylene-decene copolymers, ethylene- Examples thereof include vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-vinyl acetate-methyl methacrylate copolymer, and ionomer copolymer. These resins can be used alone or as a blend.

The thickness of the film 1 can be 20 to 200 μm. 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 reduced, and if it exceeds 150 μm, the flow path resistance increases, and it is difficult for air to flow out.

Since the film 1 has the small holes 2, 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 the diseases of the agricultural products caused by the rainwater fluffing.

The hydrophilic film can be formed by applying a hydrophilic coating solution containing an inorganic hydrophilic colloid substance and a hydrophilic organic compound as main components.

Examples of inorganic hydrophilic colloid materials are 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 hydrophilic organic compounds include various surfactants (nonionic, anionic, cationic) and hydroxyl group-containing vinyl monomer components as main components, and acid group-containing vinyl monomer components in the range 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, the hydrophilic coating liquid for forming the hydrophilic film may contain other components such as an ultraviolet absorber, a colorant, a pesticide, and a fertilizer as long as the effect of the hydrophilic film is not impaired.

The hydrophilic coating liquid may be applied so as to cover at least a part of the small holes of the film 1, or may be applied to the entire one side or both sides of the film 1. At this time, from the viewpoint of more effectively moving the rainwater, the rainwater can be applied even inside the small holes.

Examples of the method of applying the hydrophilic coating liquid include spray coating, brush coating, and roll coating.

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

If necessary, various additives can be added to the film 1. Specific examples thereof include inorganic fillers (calcium carbonate, various hydrotalcite compounds, talc, silica, alumina, zeolite, etc.), lubricants, antiblocking agents, non-dripping agents and the like.

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

In the present invention, slit holes may be used instead of the small holes. Even when the slit holes are used, a plurality of slit holes are formed on the entire surface of the strip-shaped film. This will be described with reference to FIGS. 3 and 4.

FIG. 3 is a view showing another example of the agricultural film according to the present invention, in which 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 or more and 15 mm or less, preferably 7 mm or more and 12 mm or less. The width of the slit hole is 0.1 mm or more and 0.8 mm or less, preferably 0.2 mm to 0.4 mm.

Since the slit hole 2'has the above-mentioned length and width, the same function as that of 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 area of the film.

In the case of the slit holes 2', it is preferable that a plurality of slit holes are radially arranged to form a slit group.

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

FIG. 4 is a diagram for explaining a configuration example of a slit group, FIG. 3(a) is an example of a slit group formed by five slit holes, and FIG. 3(b) is formed by six slit groups. An example of each slit group is shown.

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

The slit hole 2'is opened with a predetermined opening area. That is, the slit hole 2'has an opening area in a state of being placed flat, unlike a simple cut. Therefore, the aperture ratio defined by the present invention can be achieved. Such slit holes 2 can be preferably formed by laser processing.

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

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

The configuration of the slit group is not limited to the above example and can be various forms. For example, a slit group may be formed by forming a further slit hole outside the plurality of slits forming the above-mentioned slit group or between the plurality of slits.

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 may 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 agricultural film material (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.

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

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

(Film 2)
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 in place of the round hole in the film 1.
Here, similarly to the one shown in FIG. 4A, a slit group (pentagon) is constituted by five slit holes radially arranged. A plurality of such slit groups were formed on the entire film so that the aperture ratio was 1%.

(Film 3)
A film 3 was obtained in the same manner as the film 2 except that a slit group (hexagon) was composed of 6 slit holes in the film 2 as in the case shown in FIG. 4( b ). In comparison with the film 2, the aperture ratio was changed from 1% to 1.2% as the number of slit holes forming the slit group was increased from 5 to 6.

(Film 4)
A film 4 was obtained in the same manner as the film 1 except that the aperture ratio of 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 spreading and film coating internal environment test Films 1 to 5 were spread on tunnel frames to form agricultural tunnels 1 to 5.

For each of the agricultural tunnels 1 to 5, the lowest temperature and the highest temperature inside the tunnel and the lowest temperature and the highest 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 (sunny)

(2) Test date: March 16 (cloudy)

<Evaluation>
When the temperature is high, the tunnel 4 having an opening ratio of 2% can suitably ventilate the inside of the film coating to suppress the temperature rise (Table 1), but since air always flows in and out through the opening portion, Almost no heating effect can be obtained (Table 2).

The tunnel 5 having an opening ratio of 0% seals the inside of the film and thus exerts a preferable temperature rise effect (Table 2). On the other hand, since there is no inflow or outflow of air, when the outside air temperature rises, The temperature rises too much (Table 1).

On the other hand, in the tunnels 1 to 3 with the opening ratio of 1%, the temperature rise in the film is increased when the outside air temperature rises while obtaining the same temperature increase effect as the tunnel 5 with the opening ratio of 0% (Table 2). It can be suppressed (Table 1).

This is because the films 1 to 3 used for the tunnels 1 to 3 have aperture ratios within the range of the present invention, so that heat retention and ventilation can be switched depending on the conditions of the outside temperature. This effect can be switched when the temperature difference between the inside of the film coating and the outside of the film coating becomes about 10°C.

When the air inside the film coating is heated higher than the air outside the film coating by 10° C. or more, the small holes and the slit holes move the heated air inside the film coating from the inside of the film coating to the outside of the film. 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 (3)

Agricultural film consisting of a band-shaped film, which is used by spreading it so as to cover from the ground to the top of the inner space of the house or tunnel ,
A plurality of small holes having a diameter of 0.5 mm or more and 4.0 mm or less are formed on the entire surface of the band-shaped film, and the aperture ratio by the small holes is 0.5 to 1.5% (0. 5 to 0.8% range is excluded) ,
An agricultural film having a structure capable of keeping warm and ventilating depending on the condition of the outside temperature . Agricultural film consisting of a band-shaped film, which is used by spreading it so as to cover from the ground to the top of the inner space of the house or tunnel ,
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 band-shaped film, and the aperture ratio by the slit holes is 0.5 to the entire area of the film. It is provided to be 1.5% (excluding the range of 0.5 to 0.8%) ,
An agricultural film having a structure capable of keeping warm and ventilating depending on the condition of the outside temperature . The agricultural film according to claim 2, wherein the slit holes are formed by arranging a plurality of slit holes radially to form a slit group.

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