JPS5932492B2 - agricultural film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an agricultural film, that is, a covering material for greenhouse cultivation, mulch cultivation, tunnel cultivation, etc.
In particular, it relates to those whose heat retention properties have been improved by the use of additives.

Films conventionally used as agricultural films include mainly polyvinyl chloride films, polyethylene films, and ethylene-vinyl acetate copolymer films.

Polyvinyl chloride has high mechanical strength and good heat retention properties, so it has been used most often, mainly in hamu cultivation.

However, polyvinyl chloride film has drawbacks such as the plasticizer added to polyvinyl chloride flowing out during the period of use, resulting in soil contamination or generation of hydrochloric acid gas during incineration. In addition, polyethylene film is free from soil contamination caused by plasticizers, which is a disadvantage of polyvinyl chloride.
It is used for a variety of purposes because it does not generate toxic gas during incineration, is inexpensive, and has excellent processability. However, the biggest drawback of polyethylene film is that it has poor heat retention. In addition to the advantages of polyethylene film, ethylene-vinyl acetate copolymer film has other advantages such as slightly better heat retention and greater mechanical strength than polyethylene film. It is widely used for cages, greenhouse linings, tunnel cultivation, mulch cultivation, etc. However, its heat retention properties are comparable to polyvinyl chloride, and its use as house covering films, which require heat retention properties, is currently limited. Here, heat retention refers to the ability of agricultural films to insulate, absorbing solar heat during the day and preventing heat from radiating at night from the hardened earth.

Up to now, many methods have already been proposed for improving the heat retention properties of polyolefin agricultural films.
For example, addition of a polymer compound (JP-A-52-10595
3, JP-A-54-7114, JP-A-55-
118941, etc.) or the addition of inorganic fillers (
Japanese Patent Publication No. 47-13853, Japanese Patent Publication No. 49-1058
No. 43, JP-A-54-60347, JP-A-Sho. 5
4-71147, etc.). However, the addition of a polymer compound increases costs, reduces processability, and may lower mechanical strength. Additionally, when adding inorganic fillers, it is difficult to remove the water content, especially in silicon dioxide-based fillers.
It may cause foaming during film formation, which may impair processability. In order to solve these problems, the present inventors completed the present invention as a result of intensive research to obtain a polyolefin agricultural film with extremely excellent heat retention properties. The present invention will be explained in more detail below.

(1) Substrate The present inventors have found that barium sulfate is effective when added to various substrates conventionally used as agricultural films.

However, as described below, the present invention is most effective when polyethylene or ethylene monovinyl acetate copolymer, which is an olefin resin, is selected as the base material.

Here, the polyethylene may be any of low density polyethylene, medium density polyethylene, and high density polyethylene. Moreover, ethylene monovinyl acetate copolymer is more preferable than these because it has excellent low temperature flexibility, transparency, weather resistance, etc.

The ethylene monovinyl acetate copolymer used has a vinyl acetate content of 5.0 to 30.0% by weight, MIl. O~
20.0 and it is a mixture of polyethylene and ethylene monovinyl acetate copolymer without any problem. (2)
Barium sulfate Barium sulfate includes precipitated barium sulfate, which is produced through a chemical reaction with barite powder obtained by crushing naturally occurring barite. , is preferable from the viewpoint of film transparency.

If the amount of barium sulfate added is small, the heat retention effect will be low, but if the amount added is large, the transparency will deteriorate, making it unsuitable for applications that require transparency. That is, in practical terms, barium sulfate may be added in an amount of 1 to 20 parts by weight, preferably 1 to 10 parts by weight, per 100 parts by weight of the base material using a roll, roll, or the like. Barium sulfate is inexpensive, is registered on the positive list for food containers and packaging made of synthetic resins such as polyolefin, and is safe in terms of toxicity. It has good kneading properties with polyolefins, making it easy to form compounds, and the water content is very low at 0.15%.Therefore, there is no tendency for water-containing substances, such as silicate additives, to foam during film processing. The processability of the film is excellent. (3) Other Additives The agricultural film of the present invention can also contain various additives that are commonly used to improve various properties required for agricultural films.

For example, when polyethylene or ethylene monovinyl acetate copolymer is used as the base material, benzophenone-based, benzotriazole-based, etc., or modified UV absorbers and antioxidants are added to the base material as iron resistance improvers. It is preferable to add 0.1 to 1.0 parts by weight, preferably 0.2 to 0.8 parts by weight per 100 parts by weight. In addition, as a droplet-free agent, glycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid modified ester, and various surfactants of these modified products are added in an amount of 02 to 30 parts by weight, preferably 0.5 to 30 parts by weight, per 100 parts by weight of the base material. It is preferable to add 1.5 parts by weight. As anti-blocking agents, zinc stearate,
Calcium stearate, stearate amide, white carbon, etc. are preferably added in an amount of 02 to 5 parts by weight, preferably 0.2 to 30 parts by weight, per 100 parts by weight of the base material. In addition, colorants, lubricants, etc. may be used depending on the purpose.

(4) Forming force method The agricultural film of the present invention combines a base material and barium sulfate,
After melting and kneading with a Banbury No. 1 kneader, it can be produced into a film by a normal film forming force method such as inflation, T-die method, calender method, etc.

The above-mentioned weather resistance improvers, dropless agents, blocking anti-fat agents, etc.
When using other additives, for example, they may be mixed together with barium sulfate, or they may be mixed into the existing base material. As described in detail above, the agricultural film of the present invention has heat retention properties without impairing the properties of the base material (mechanical strength, thermal adhesion properties, droplet resistance, weather resistance, surface smoothness, etc.). It is extremely useful as a covering material for greenhouse horticulture for required greenhouse cultivation, mulch cultivation, tunnel cultivation, etc.

Hereinafter, the present invention will be explained using specific examples; however, the present invention is not limited to these specific examples in any way.

Example 1 Ethylene monovinyl acetate copolymer (Kikyo Soda Kogyo Co., Ltd.)
100 parts by weight of barium sulfate (manufactured by Sakai Chemical Industry Co., Ltd., precipitated barium sulfate #100, average particle size 06μ) 5 Parts by weight were added, kneaded in a Banbury 1, cooled to form a pellet, and a film with a thickness of 75 μm was produced using the inflation method at a resin temperature of 160 to 180°C, and this was used as Example Sample 1. did.

Example 2 The same procedure as in Example 1 was carried out except that the ethylene monovinyl acetate copolymer in Example 1 was changed to low density polyethylene ("Petrocene 170" manufactured by Toyo Soda Kogyo Co., Ltd., M = 1.0). A film having a thickness of 75 μm was produced, and this was designated as Example Sample 2.

Comparative Example 1 For comparison, a film with a thickness of 75 μm was produced using only the ethylene monovinyl acetate copolymer of Example 1, and this was designated as Comparative Example Sample 1.

Comparative Example 2 A film with a thickness of 75 μm was produced using only the low density polyethylene of Example 2, and this was designated as Comparative Example Sample 2.

The mechanical strength and thermal adhesiveness of the samples of Examples 1 and 2 and Comparative Examples 1 and 2 were measured, and the results are shown in Table 1.

The measurement method in Table 1 was performed as follows.

Tensile strength, elongation, and right angle tear strength were measured vertically and horizontally based on JIS K678l. Thermal adhesiveness was measured using a heat sealer with a temperature gradient and a sealing pressure of 1k9/CT.
iI, the film is sealed for a sealing time of 5 minutes, and the sealing temperature at which the sealing strength is 4009/1571111t or higher is defined as thermal adhesiveness.

In Table 1, there is no difference in mechanical strength between Example Samples 1 and 2 of the present invention and Comparative Example Samples 1 and 2, respectively.

Furthermore, there was no difference in thermal adhesion, and no deterioration in the physical properties of agricultural films was observed due to the inclusion of barium sulfate. This can be said to be preferable as it does not inhibit the Next, regarding heat retention, each sample was covered in a sealed underground tunnel and the air temperature inside and outside the tunnel and the ground temperature were measured.
The results are shown in Table 2.

The heat retention properties in Table 2 were measured as follows.

The heat retention properties were shown by the air temperature inside and outside the tunnel and the ground temperature, which were created by enclosing each sample in the arch-shaped frame structure shown below.

The arch-shaped frame construction body was made from a polystyrene foam board with a thickness of 100 WI, and was made by filling river sand into an open-bottomed box with internal dimensions of 500 mm width, 700 mm length, and 170 mm height.
The outside of the foamed polystyrene part is covered with a 1.2Wt thick iron plate, and a 6mm diameter and 11mm length is placed on top of this box.
It is made of iron rods (0071111) with arch-shaped frames installed at four locations. The temperature inside and outside the tunnel and the ground temperature were measured at 20 CIn above ground and 5 CIn underground (17 CIn).
71 and continuously recorded with a resistance type automatic recording thermometer, 2 times a day.
The maximum temperature, minimum temperature, and average temperature were determined from the hourly measurements four times.

The measurements were conducted from April 11th to 12th, 1982 in Shinnanyo City, Yamaguchi Prefecture. In Table 2, Samples 1 and 2 of the present invention have a particularly effective effect on improving the minimum soil temperature compared to the base resin films (Comparative Samples 1 and 2), which is important for soil temperature in cultivation in the cold season. [low]
can be prevented.

As described above, the agricultural film of the present invention is characterized by adding and mixing 1 to 20 parts by weight of barium sulfate to 100 parts by weight of polyethylene or ethylene monovinyl acetate copolymer. It is a film that maintains thermal adhesiveness without impairing the mechanical strength of the base material, has good kneadability with polyolefin, and has good film processability of the compound.

Claims (1)

[Scope of Claims] 1. An agricultural film prepared by adding and mixing 1 to 20 parts by weight of barium sulfate to 100 parts by weight of a base material made of an olefin resin. 2 Olefin resin is polyethylene or ethylene-
The agricultural film according to claim 1, which is a vinyl acetate copolymer.