JPS5937016B2 - Agricultural coating film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention improves and improves the heat retention of a polyolefin resin film used as a covering material for growing plants.
Specifically, the present invention relates to an agricultural covering film that improves the growth of plants by increasing soil temperature during the day and preventing a drop in soil temperature at night.

Sunlight enters in the wavelength range of approximately 0.3 to 3μ, is absorbed by objects, and is converted into thermal energy, warming soil and crops during the day, but these soil and crops are almost black bodies. Due to its close proximity, it emits far-infrared rays of about 3 to 25 microns into the outside air, where the temperature drops at night.

For this reason, conventional agricultural covering films for agricultural greenhouses, tunnels, multi-ferns, etc. for the purpose of forced cultivation have been made using glass plates and vinyl chloride, which have excellent shielding effects in the far infrared region of about 3 to 25μ to prevent heat radiation at night. The film is used to prevent heat from escaping during the night.

However, the use of glass plates is limited because they are expensive and difficult to process and handle.

In addition, it is difficult to manufacture ultra-thin films using vinyl chloride resin, and during use, the plasticity contained in the film bleeds onto the film surface, causing dust to adhere and significantly impairing the transmission of sunlight. Its use is limited due to its flaws such as easy breakage. In recent years, with advances in agricultural technology, plastic films have come to be widely used as agricultural covering materials. In particular, polyolefin resin films are suitable for a variety of uses because they are easy to obtain raw materials, can be manufactured into ultra-thin films, and are easier to dispose of as waste after use than vinyl chloride films. It is used. However, the transmittance in the far infrared region of 5 to 25 μm was as high as 70 to 80%, and compared to the transmittance of vinyl chloride film of about 15%, the heat retention effect at night was extremely poor as a coating film. Therefore, as mentioned above, 5 to 25μ
It has been proposed to add silicic anhydride, alumina silicate, anhydrous aluminum oxide, and phosphate to polyolefin resins, which have absorption bands in the wavelength region of is narrow, and when using the aforementioned additives, the particle size is small, generally 0.1
The material used is less than μ, so it is bulky and easily scatters when mixed with resin, making it undesirable for work.
Film forming using the masterbatch method tends to result in poor diffusion of the masterbatch and uneven far-infrared absorption.

Therefore, in order to effectively shield the far infrared rays of 5 to 25μ, the effect cannot be obtained unless at least 30 parts of the above-mentioned additives are added to 100 parts by weight (hereinafter abbreviated as parts) of the polyolefin resin. Ta. However, when large amounts of anhydrous silicic acid, anhydrous aluminum silicate, phosphates, etc. are added to polyolefin resins, they inhibit the penetration of sunlight and also reduce physical properties such as mechanical strength and weather resistance. Since the practical value as an agricultural covering film would be lost, the amount of these additives used had to be reduced to 20 parts or less at the expense of shielding from far infrared rays. For this reason,
Conventional agricultural covering films using polyolefin resins have difficulty achieving far-infrared transmittance comparable to that of vinyl chloride films, resulting in inadequate nighttime heat retention and significantly lowering product value. Ta. The present inventor has improved the above-mentioned drawbacks and has developed an agricultural coating using a polyolefin resin that substantially blocks the far infrared rays of about 5 to 25μ without substantially blocking sunlight during the day, and with less deterioration in physical properties. As a result of intensive research to develop the film, they discovered that the purpose could be achieved by adding and kneading a specific inorganic substance to a polyolefin resin in a specific ratio and molding it into a film, and completed the present invention. .

In other words, one or more of (A) calcium carbonate, (B) silicic anhydride, silicate compound calcium sulfate, and (O) aluminum hydroxide are added to 100 parts of polyolefin resin. ):(C)=10:3~30:3~3
This is an agricultural coated film formed by adding and kneading the mixture in a proportion of 0 and 5 to 25 parts by weight of (A)+(I+(C)-).

In the present invention, the three components (A), (3), and (C) are mixed in a ratio of 10:3 to
Approximately 5 to 25 by using the ratio of 30:3 to 30
It is possible to almost block the far infrared region of μ, and 3
If even one of the components (A), (B), (O) is missing or out of range, the shielding effect in the far infrared region will be reduced,
This is undesirable as it reduces nighttime heat retention.

In particular, when melt-kneading the three components (A), (B), and (C) in the above proportions with the polyolefin resin, (by using aluminum hydroxide as the component 0) in the polyolefin resin (. The kneading of A), (B), (03 components becomes very easy, and (A), (day, (03)
The components are dispersed in a completely uniform state, making it possible to obtain an agricultural covering film with excellent shielding effects in the far-infrared region, which cannot be obtained with conventional agricultural heat-insulating films using polyolefin resins.

Furthermore, since each component (A), (l, and (C)) is uniformly dispersed, (A),
B), (Even if the total amount of component 03 added is small, the heat retention effect as an agricultural coating film can be sufficiently exhibited, so the total amount added is 5 to 25 parts per 100 parts of polyolefin resin.
%, preferably 10 to 20 parts, it is possible to obtain a film that has a far-infrared shielding effect superior to that of vinyl chloride film and hardly obstructs sunlight during the day, and also has improved mechanical strength. Also, a highly practical agricultural covering film can be obtained which is improved compared to agricultural films using conventional polyolefin resins. If the total amount of the three components (A), (B), and (C) is less than 5 parts per 100 parts of the polyolefin resin, a satisfactory heat retention effect will not be obtained, and if it exceeds 25 parts. is undesirable because it blocks the transmission of sunlight during the day and significantly reduces the weather resistance of the film.

Examples of the polyolefin resin of the present invention include high-pressure polyethylene, medium-low-pressure polyethylene, low-pressure polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and the like. Among these, high-pressure polyethylene and ethylene-vinyl acetate copolymers are particularly preferred as agricultural coating films because they yield films with superior transparency and flexibility compared to other resins. Components (A), (B), and (03) used in the present invention include light calcium carbonate, heavy calcium carbonate, whitening, etc., with an average particle size of around 0.15μ as (A). Light calcium carbonate is preferred.

Examples of (B) include silicic anhydride, calcium sulfate, and silicic acid compounds such as talc, clay, mica, etc., and those having an average particle size of 0.5 to 5 μm are preferred. (C) is aluminum hydroxide having an average particle size of 0.1 to 10 microns, preferably 0.5 to 5 microns. To manufacture the film, a mixture of polyolefin resin and components (A), (B), and (03) at a certain ratio is melt-kneaded using a Banbury mixer, a roll, or an extruder, and then subjected to inflation processing. , and is formed into a film using a normal forming method such as T-die processing.

The thickness of the film varies depending on the application, such as house,
50-200μ for tunnel use, 10-4 for multi use
0μ is preferred.

The film using polyolefin resin obtained by the present invention has three components (A), (B), (
Since additives having a particle size larger than that of additives used in conventional products can be used, there is no scattering during kneading with resin, and the working environment is greatly improved, which is preferable.

When the film using polyolefin resin obtained by the present invention is used as a covering film for various types of houses, tunnels, mulches, etc., its heat retention is comparable to that of vinyl chloride film, and it is easy to dispose of after use. It is extremely useful as an agricultural covering film.

The agricultural coated film obtained by the present invention may contain appropriate stabilizers, ultraviolet absorbers, antistatic agents, etc., if necessary.

Next, the present invention will be explained with reference to Examples.

Example 1 20 parts of high-pressure polyethylene (M [value 4, density 0.920, used in each example and reference example hereinafter)] (A): (B): (
C) -1:l:l (A) calcium carbonate with an average particle size of 0.145μ, (B) talc with an average particle size of 0.8μ, and (C) aluminum hydroxide with an average particle size of 3μ. A total of 18 parts (6 parts each) were added and melted and kneaded with two heated rolls to produce a masterbatch. 80 parts of high-pressure polyethylene was added to this and melted and kneaded, and this blend was formed into a film with a thickness of 100μ by inflation extrusion molding. obtain.

Example 2 The same as Example 1 except that the high-pressure polyethylene in Example 1 was replaced with ethylene vinyl acetate copolymer (MI value 1.7, density 0.938).

Example 3 The mixing ratio of the three components (A), (B), and (C) in Example 1 was (A):(B):(C)-1:2:2,
Everything was the same as in Example 1 except that the amounts used were changed to 3 parts of (A) and 6 parts each of (B) and (C) for a total of 15 parts.

Reference Example 1 The mixing ratio of the three components (A), (B), and (C) is the same as in Example 1. Everything else is the same as in Example 1.

Reference Example 2 The mixing ratio of the three components (A), (B), and (03) is the same as in Example 1, and the usage amounts of the three components (A), (B), and (C) are 10% each.
Everything is the same as in Example 1 except that each copy is changed to 30 copies in total.

Reference Example 3 The mixing ratio in Example 1 was (A):(l:(0-1:4:
4, and the amount used is (A) 2 parts, (B) and (6) each 8 parts.
Everything is the same as in Example 1 except that each part is changed to 18 parts in total.

Reference Example 4 Calcium carbonate with an average particle size of 0.14μ and silicic anhydride with an average particle size of 0.02μ are added to 20 parts of high-pressure polyethylene.
Add 12 parts each of aluminum oxide (36 parts in total) and melt and knead with two heated rolls to produce a masterbatch. To this, 80 parts of high-pressure polyethylene was added and melt-kneaded, and this mixture was extruded into a thick layer by inflation extrusion molding. Ki100
Obtain a film of μ.

As described above, the average visible light transmittance and heat retention were measured for the agricultural covering films of the present invention obtained in Examples 1, 2, and 3 and the comparative films of Reference Examples 1, 2, 3, and 4. Table 1 shows the average soil temperature under each film covering for 10 days from mid-March in Omiya City, Saitama Prefecture, and Table 2 shows the diffusivity of the masterbatch.

Claims (1)

[Claims] 1 To 100 parts by weight of polyolefin resin, one or more of (A) calcium carbonate, (B) silicic anhydride, and silicate compound calcium sulfate (C) aluminum hydroxide (A):(B):( C)=10:3~30:3~
An agricultural covering film formed by kneading and molding the mixture in a ratio of 30 parts by weight and (A) + (B) + (C) = 5 to 25 parts by weight.