JPS6183243A - Heat insulating film for agriculture - Google Patents

Abstract

PURPOSE:To provide the title film, by molding a thermoplastic resin incorporated with a resin having high water absorption and giving the mixture a particular permeability to infrared rays. CONSTITUTION:1-30pts.wt. resin with high water absorption (SUMIKAGEL A-20 prepd. by SUMITOMO CHEMICAL Co.) is added to 100pts.wt. thermoplastic resin (e.g., vinyl acetate copolymer resin) to form a film by inflation, etc. Raw resins and compsns, are selected so that the permeability to infrared rays after water absorption of the resulting film is 50% or below as the mean value within the wavelength range of 7-15mu. When used as a coating film for agricultural houses, etc., said film is excellent in heat insulation at night and therefore does not cause condensed water dripping, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an agricultural heat-retaining film, and more particularly to an agricultural heat-retaining film made by blending a thermoplastic resin with a superabsorbent resin. .

Generally, agricultural greenhouses or tunnels (hereinafter referred to as "houses" or "tunnels") are used for cultivation, etc.
7. Since it inhibits the photosynthesis of crops and reduces their growth, it is desirable to have a film with high light transmittance and excellent heat retention when it gets cold at night. It will be done.

In other words, during the day, the sun's rays are taken in to warm the crops and soil inside the greenhouse and tunnel, and then at night. jf sends warm air to the house,
It is necessary to prevent it from escaping outside the tunnel.

Polyethylene and ethylene-vinyl acetate copolymer films have been widely used as agricultural films along with vinyl chloride, but both polyethylene and ethylene-vinyl acetate copolymers have inferior heat retention properties compared to vinyl chloride, and are not suitable for plants. It is considered disadvantageous in terms of cultivation and growth.

This difference in heat retention is thought to be due to the following reasons.

During the day, sunlight enters with a wavelength range of 0.3 to 3 ft., and with the exception of some ultraviolet rays, most of the rays pass through the covering material and reach the facility, damaging crops and soil. Heat is radiated from these during the warming night.

In this case, since the emissivity of the crop leaves and leaves is 0.9 or higher, it can be regarded as a black body, and the radiation energy from the black body can be considered by applying all six values.

The distribution of black body radiation glands with a hot water temperature of about 13 to 27 pO is 3 to 3.
30/J and the peak is 9-1j7u. Therefore, it is believed that the infrared transmittance in the wavelength range centered around this wavelength completely controls the heat retention properties of the film.

In the present invention, by adding a super absorbent resin to the thermoplastic resin 11 film, after spreading the film in a house, tunnel, etc., it absorbs moisture such as condensation water and water vapor, and the infrared wavelength range 7, which completely dominates the heat retention property. It improves heat retention by reducing infrared transmittance by ~15%, and also makes the entire surface of the film hydrophilic, improving droplet flow and preventing the outbreak of pests and diseases caused by condensed water falling on crops. be.

[Conventional technology]

The infrared transmittance of films made of polyvinyl chloride, polyethylene, ethylene-vinyl acetate copolymer resin, etc. does not differ much in the wavelength range shorter than 6I, but in the range of 7 to 67 or more.
A remarkable difference is observed in the long wavelength region of 157t.

For example, when considering soft polyvinyl chloride that contains relatively many additives, the average infrared transmittance in the wavelength range of 7 to 15 nm is 15 to 15 nm due to the synergistic effect of various additives such as heat stabilizers and plasticizers. While it is 20%, polyethylene is 75~
80%, and 55% to 55% for ethylene vinyl acetate copolymer resin
It is about 60%, and when compared to the above conditions, it can be said that polyethylene is close to zero in terms of nighttime heat retention.

For the above reasons, attempts have been made to improve the heat retention properties of thermoplastic resins, such as polyethylene and ethylene-vinyl acetate copolymer resin films, by improving the above-mentioned wavelength range 7 to lZ. We still haven't gotten enough.

[Problems to be solved by the present invention]

The infrared wavelength range of general agricultural films, namely polyethylene films and ethylene/vinyl acid copolymer resin films, is 7 to 157! The infrared transmittance of is over 80%, respectively.
It is 50% or more, which is close to zero in terms of nighttime heat retention, and there is a practical problem as a heat retention film.

Furthermore, since the surface of the film is hydrophobic, there is a disadvantage that dew condensation occurs on the inner surfaces of greenhouses, tunnels, etc., and falling water droplets are likely to wet crops and cause pests and diseases.

Therefore, when these films are used, heat retention is poor, resulting in cold and cold temperatures at night, stagnation of crop growth due to frost in winter, growth problems such as damage due to frost, and the occurrence of pests and diseases.

[Means for solving problems]

In the present invention, 100 parts by weight of a thermoplastic resin is mixed with 1 part by weight of a super absorbent resin.
After the film obtained by adding ~30 parts by weight, preferably 2 to 15 parts by weight, is spread in a house, tunnel, etc., 17)+llt'? It absorbs moisture such as dew water and water vapor, and the infrared wavelength range is 7 to 157. It lowers the average infrared m transmittance of 1 to 50% or less and improves heat retention.

[For production]

In the present invention 1, the infrared rays of the film range from 7 to 15/
If the average infrared transmittance of l exceeds 50%, there will be almost no substantial heat retention effect against the cold nights, and the warm air emitted from crops and soil heated by sunlight during the day will not pass through the film. This dissipates and lowers the temperature inside the Hau at night.

Therefore, crops in greenhouses and tunnels are susceptible to growth stagnation or damage caused by the sieve boxes.

When the infrared transmittance of the infrared wavelength range 7 to 15/(, which governs heat retention) is less than 50%, the warm air warmed by the sun's rays is blocked by the film surface, and the heat is retained without being transmitted and dissipated outside the house or tunnel. Improved crop growth and quality without stagnation of crop growth and no damage due to frost etc. - Improved ff quantity and bttx The interior of greenhouses and tunnels becomes humid and the dew condensation that forms on the film surface is absorbed, making the film surface hydrophilic, which improves the flow of condensed water inside greenhouses and tunnels, and prevents condensed water from falling onto crops. It is possible to prevent the occurrence of pests and diseases.

If the amount of the superabsorbent resin used in the present invention is less than 1 part by weight, even if the superabsorbent pine resin absorbs water, no practical heat retention effect can be obtained.

Therefore, as mentioned above, growth problems such as stagnation of crop growth and/or damage due to frost and the like are likely to occur.

Furthermore, if the amount of superabsorbent resin added exceeds 30 parts by weight, the film will not have practical strength after water absorption, and the durability will decrease during long-term use, which is undesirable as an agricultural film.

The superabsorbent resin used in the present invention may be any known natural, semi-synthetic, or synthetic polymer, as long as it absorbs water tens to thousands of times its own weight, such as synthetic resin polyvinyl alcohol. Fur-based products, polyacrylic acid-based products, polyamide-based products, polyethylene oxide-based products, saponified polyacrylonitrile products, starch-based acrylonitrile grafts [
Examples include saponified products of i-compounds, acrylic acid grafted products, cellulose-based graft polymerized products, carboxymethylated products, etc., and are not limited to these.
There is no problem in using one species or a combination of two or more species.

As the thermoplastic resin used in the present invention, polyolefin resins, polyvinyl chloride, polybutene or copolymers thereof, ethylene-acrylic copolymers, ethylene-butylene copolymers, etc. can be used.

Examples of the polyolefin resin used in the present invention include ethylene-vinyl acetate copolymer resin, low-density polyethylene resin, and linear low-density polyethylene resin, with ethylene-vinyl acetate copolymer resin being particularly preferred.

Naturally, those with high vinyl acetate content have an infrared wavelength range of 7 to 1.
5) The infrared wavelength range of the light is low, and the heat retention is effective as it has a synergistic effect.

However, if the vinyl acetate content is 30% by weight or more, the resulting film is susceptible to prolagging and has problems such as not being able to obtain practical strength as an agricultural film, which is not preferred from a practical standpoint.

In addition, the agricultural heat-retaining film of the present invention may contain conventional antioxidants, stabilizers, plasticizers, lubricants, colorants, droplet agents and other additives, if necessary.

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

Example 1 To 100 parts by weight of ethylene-vinyl acetate copolymer resin (EVQ D2021, manufactured by Sumitomo Chemical Co., Ltd.), 10 parts of a super absorbent resin (Sumikagel A-20, manufactured by Sumitomo Chemical Co., Ltd.) was added, and 50 f. An entire film having a thickness of 100 ft was obtained as Example Sample 1 using an extruder using a conventional inflation method.

Example 2 A super absorbent resin (Sumikagel A-4, manufactured by Sumitomo Chemical Co., Ltd.) was added to 10,000 weight of agricultural ethylene vinyl acetate copolymer tree 111T (Ebatate H2O21K, manufactured by Sumitomo Chemical Co., Ltd.).
0) was added, and 15 parts by weight of
A film of 00/-+ was obtained and designated as Example Sample 2.

Example 3 7 parts by weight of a super absorbent resin (Sumikagel A-40, manufactured by Sumitomo Chemical Co., Ltd.) was added to 1100 parts by weight of linear low-density polyethylene (Tsurtozex 3021F1, manufactured by Mikata Petrochemical Co., Ltd.), and 65 parts by weight were added. Extruder T-die method 1 Trowel 100 mm, t film was obtained and used as Example sample 3 〇Example 4 In Example 1, low density polyethylene (Sumitomo Chemical Co., Ltd.) was used instead of the ethylene vinyl acetate copolymer resin. Example sample 4 having a thickness of 100// was obtained in the same manner as in Example 1, except that the sample was replaced with Sumirikisen JF208-9) manufactured by Sumiki Sen JF208-9).

Comparative Examples 1 to 3 Films with a thickness of 100 mm were obtained in the same manner as in Examples 1 to 3, except that the superabsorbent resin was removed, and Comparative Example Samples 1.2. It was set as 3.

Comparative Example 4 Comparative Example Sample 4 with a thickness of 1007 mm was carried out in the same manner as in Example 4, except that the super absorbent resin (Sumikagel A-20 manufactured by Jusumikagaku Co., Ltd.) was replaced with 2 parts by weight of silicic anhydride. I got everything.

The samples obtained in Examples 1 to 4 and Comparative Examples 1 to 4 and the samples were left in a room with a humidity of 99%, and the infrared transmittance in the infrared wavelength range 7 to 15A was measured using an infrared spectrophotometer in a water absorption equilibrium state. (R-400 manufactured by Shimadzu Corporation), and the average values are shown in Table 1.

Table 1 Infrared suitability rate (%) Next, in order to compare the moisture retention properties of each sample of Examples and Comparative Examples, an agricultural tunnel, that is, height 6°Cff1 width 120a
A semicircular tunnel with a length of 5 m was set up, and the ground temperature and air temperature inside the tunnel were measured.

The measurement results are shown in Table 2.

The above measurements were conducted in Marugame City, Kagawa Prefecture for 10 days from November 7th to November 17th, 1982.

The temperature inside the tunnel was measured at a position of 3 Qom above the ground, and the underground temperature inside the tunnel was measured with a sensor located at a depth of 5 cm underground, and an automatic temperature recorder (12-point recorder manufactured by Chino Seisakusho Co., Ltd.) was used to record the highest and lowest temperatures. The temperature was measured, and the average temperature 2 was calculated and shown in Table 2.

Table 2 [Effects] In view of the results of the above examples and comparative examples, in the comparison of infrared transmittance in Table 1, the decrease in infrared transmittance of the example samples in the water absorption equilibrium state is remarkable compared to the comparative examples, Therefore, at night, it is difficult for warm air to penetrate inside the house or tunnel, so it has an excellent heat retention effect.

In addition, the example sample of the underground temperature inside the tunnel due to the tunnel expansion exhibited a higher thirst than the comparative example sample in terms of both the minimum temperature and the average temperature.

If the minimum temperature and the average temperature are, for example, 0.4 to 1.200 higher, there will be a really large difference in moisture content over a long period from sowing to harvesting, and this will result in poor growth, flowering, fruiting, etc. of the crops. From a general perspective, it does not have a major impact, and the effect of increasing crop yields and bringing forward the harvest time is extremely significant.

German patent originator

Claims (2)

[Claims] (1) An agricultural film made by adding 1 to 30 parts by weight of a super absorbent resin to a thermoplastic resin is characterized in that the average infrared transmittance in the infrared wavelength range of 7 to 15μ after water absorption is 50% or less. A heat-retaining film for agricultural use. (2) The agricultural heat-retaining film according to claim 1, wherein the thermoplastic resin is a polyolefin resin.