JP3094296B2 - Agricultural film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an agricultural film.

[Conventional technology]

Agricultural films used for greenhouse and tunnel cultivation include polyvinyl chloride (PVC), branched low-density polyethylene (LDPE), ethylene-vinyl acetate copolymer (EV
A) A soft plastic film with a thickness of about 30 to 200 µm mainly using linear low density polyethylene (LLDPE) as a base resin.

Since the inside of the house or tunnel covered with these films is saturated with the water vapor evaporating from the ground or the plant, the water vapor condenses on the inner surface of the cooled film and adheres as water droplets. When water droplets adhere, the incident sunlight is greatly reduced due to the irregular reflection, and the water droplets fall and wet the crop, causing a frequent disease.

For this reason, the film is generally subjected to a so-called water droplet prevention (hereinafter referred to as “no-drop”) process for converting the attached water droplets into a water film. At present, by using the drip-free film treated with this drip-free treatment, the amount of sunlight transmitted through the house and tunnel is increased as much as possible, the internal soil temperature and temperature are raised, photosynthesis is increased, and the crop growth is healthy. It promotes the condition and suppresses the occurrence of disease.

Conventional methods of drip-free treatment include a drip-free kneading method in which a drip-free agent is kneaded into a base resin and formed into a film, and a coating method in which a drip-free agent is coated after film formation. is there.

Of these, the drip-free film obtained by the coating method has not been put to practical use as a soft plastic film for agriculture due to its performance.

This is because even if a soft plastic film is coated with a surfactant or a hydrophilic polymer substance which has been used as a drip-free agent, the surface energy is low, so (1) poor wettability, causing a repelling phenomenon, There is a problem that it cannot be applied evenly, (2) it is washed away by water droplets attached due to poor adhesion, and its drip-free life is very short. (3) There are many sticking problems with the drip-free agent and there are many film blocking problems. This is because it is not possible to obtain an agricultural film that can be maintained for several months to one year or more.

However, in recent years, a new type of coating type dripless agent has been developed. This drip-free agent contains an inorganic hydrophilic colloid substance and a hydrophilic organic compound as main components.
These compounds are disclosed in JP-A-45432, JP-B-63-45717, JP-B-64-2158 and the like.

Examples of inorganic hydrophilic colloidal materials include colloidal silica, colloidal alumina, colloidal Fe (OH) ₂ , colloidal Sn (OH) ₄ , colloidal TiO ₂ , colloidal B
aSO ₄ and colloidal lithium silicate. Particularly preferred materials are colloidal silica and colloidal alumina.

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

This type of coating type drip-free agent is greatly improved in both wettability and adhesiveness, and the drip-free life of a film coated with the same can be made from half a year to one year or more.

[Problems to be solved by the invention]

However, the wettability and adhesion to substances with low surface energy, such as soft plastic films used for agriculture, are basically insufficient. This tendency is particularly strong in low-polarity polyolefin films such as LDPE, EVA and LLDPE films.

Therefore, for example, when a soft plastic film is spread on a house and then sprayed with a drip-free agent with a power sprayer or the like, a large amount of the drip-free agent is required, resulting in an increase in cost. In addition, the spraying operation time becomes longer. Furthermore, there are problems such as uneven spraying of the film and impairing the drip-free effect of the house. Also, when a film is applied with a coater or the like, a large amount of coating liquid is consumed, and the coating speed cannot be increased, resulting in an increase in manufacturing cost.

In order to solve such a problem, recently, a method of improving the wettability of the surface by introducing a polar group into the film surface by a chemical change due to corona discharge treatment or the like, that is, oxidation, has been adopted. However, in this method, the more the treatment is performed to improve the wettability, the more the surface of the film and the inside thereof are oxidized, and the lower the weather resistance of the film. Such a decrease in weather resistance is a fatal problem for agricultural films. Therefore, this method cannot be adopted.

As another method, there is a technique of modifying a base resin or a film surface by a chemical reaction, that is, a technique of introducing a polar group (hydrophilic group or the like). However, at present, this leads to a significant increase in cost and is applied to an agricultural film. Difficult.

The present invention has been made in order to solve such a conventional problem, and is excellent in application properties of a drip-free agent to a base film and drip-freeness after application of a drip-free agent, and is inexpensive for agricultural use. It is intended to provide a film.

[Means for solving the problem]

The agricultural film provided by the present invention is described in the following (1) and (2).

(1) A thermoplastic resin layer containing 2.0 to 15% by weight of an inorganic fine powder and a transparent layer of a thermoplastic resin containing 0.1 to 2.0% by weight of an inorganic fine powder are laminated to improve the coating property of a drip-free agent. An agricultural film obtained by coating a thermoplastic resin film with a surface-applied drip-free agent mainly composed of an inorganic hydrophilic colloid substance and a hydrophilic organic compound.

(2) A thermoplastic resin transparent layer containing 0.1 to 2.0% by weight of an inorganic fine powder is laminated on both sides of a thermoplastic resin layer containing 2.0 to 15% by weight of an inorganic fine powder, thereby improving the application property of a drip-free agent. An agricultural film obtained by coating a coated thermoplastic resin film with a surface-applied drip-free agent containing an inorganic hydrophilic colloid substance and a hydrophilic organic compound as main components.

Examples of the thermoplastic resin herein include polyolefins such as LDPE, EVA, and LLDPE, and PVC.

As the inorganic fine powder, lithium, sodium,
Oxides, hydroxides, carbonates, sulfates, phosphates, borates, silicates, aluminates of metals such as potassium, magnesium, calcium, zinc, aluminum, silicon, titanium,
And aluminosilicate. Among them, oxides include, for example, magnesium oxide, calcium oxide, aluminum oxide, silicon oxide, titanium oxide, etc., and hydroxides include lithium hydroxide, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, etc. As carbonates, magnesium carbonate, calcium carbonate, etc., and as sulfates,
Potassium sulfate, magnesium sulfate, calcium sulfate, zinc sulfate, aluminum sulfate, etc., as phosphates, lithium phosphate, sodium phosphate, potassium phosphate, calcium phosphate, etc., borate as sodium borate, etc., and silicate as silicate. Magnesium silicate, calcium silicate, aluminum silicate, titanium silicate, etc .; aluminates: sodium aluminate, potassium aluminate, calcium aluminate, etc .; aluminosilicates: sodium aluminosilicate, aluminosilicate Potassium, calcium aluminosilicate and the like can be mentioned, respectively, and further, as these complex salts, for example, basic complex salts represented by hydrotalcites represented by the following formula and the like can be mentioned.

M _1-x Al _x (OH) ₂ A _x / _n · m H ₂ O where M is a divalent metal ion selected from the group consisting of magnesium, calcium and zinc, A is an n-valent anion, and 0 <X <0.5, 0 ≦ m ≦ 2.

Among these inorganic fine powders, those having a hydroxyl group,
In particular, hydrotalcites are preferred.

The amount of the inorganic fine powder added to the thermoplastic resin film is 0.
5 to 15% by weight. If it is less than 0.5% by weight, the effect of improvement is small, and if it exceeds 15% by weight, the strength and transparency of the film are impaired. The smaller the particle size of the powder is, the more uniformly the particles are dispersed. For example, 0.5-
It is about 5μ. Conversely, when it becomes about 5-10μ in size,
Depending on the amount added, the strength and transparency of the film decrease.

Of the inorganic fine powders, hydrotalcites can have a refractive index in the range of about 1.50 to 1.55, and can be adjusted to the refractive index of the PVC film or LDPE film.
This has the advantage that the transparency of the film is hardly impaired.

As the thermoplastic resin film F, usually, as shown in FIG. 1, a material obtained by uniformly dispersing and mixing inorganic fine powder throughout the film is used, and a coating layer D of a drip-free agent is provided thereon. However, it is difficult to completely disperse and mix the inorganic fine powder.
When the content is 3% by weight or more, fine irregularities are generated on the film surface, and light is irregularly reflected, so that the transparency of the film may be reduced.

As a countermeasure, as shown in FIG. 2, the thermoplastic resin film F has a three-layer structure, and the inorganic fine powder is mainly added to the intermediate layer m. The transparent resin layers a and b may be used.

In addition, as shown in FIG.
It may have a layered structure. That is, it can be composed of the intermediate layer m and the transparent layer b in FIG.

The thickness of the transparent layer a in contact with the drip-free coating layer D in FIG. 2 must be 100 μm or less, preferably 50 μm or less, more preferably 30 μm or less. If it exceeds 100 μm, the effect of improving the wettability and the adhesion is almost lost. The reason is that the exact mechanism of the improvement effect by the inorganic fine powder has not been sufficiently elucidated, but is presumed to be due to weakening the chargeability of the film due to the electrostatic interaction by the inorganic fine powder. For this reason, even if the transparent layer a is interposed between the coating layer D of the drip-free agent and the intermediate layer m containing the inorganic fine powder, if the thickness is 100 μm or less, the effect of improving wettability and adhesion is improved. Seems to be recognized. There is no problem even if inorganic fine powder is added to the transparent layers a and b in a range that does not impair the transparency of the film, for example, 0.1 to 2.0% by weight.

The method of coating the thermoplastic resin film with the drip-free agent may be any of various roll printing methods, immersion methods, spraying methods, and the like. Also, the coating
It can be carried out by in-line coating performed after film formation, outline coating performed in a rewinding step after film formation / winding, or by spray coating the inner surface of the film after stretching.

[Action]

In the present invention, since the inorganic fine powder is previously mixed into the thermoplastic resin film as the base film, it is considered that the electrostatic characteristics of the fine powder greatly change the charging characteristics of the film surface.

For this reason, the wettability and adhesiveness of the surface-coating type drip-free agent to the thermoplastic resin film are improved, and thus the coating property of the drip-free agent is also improved. In other words, a small amount of non-drop agent widely,
It can be applied evenly, uniformly and in a short time, and the cost is low. Further, since the drip-free agent is uniformly applied without unevenness, its drip-free effect is not impaired.

〔Example〕

(Example 1) The following base film was spread on a pipe house having a width of 5.4 m, a height of 2.8 m, and a length of 50 m, and the inner surface thereof was sprayed with a drip-free agent by a power sprayer to coat the same. The drip-freeness was evaluated.

(1) Base film: LDPE (MI1.0, SG0.920) and hydrotalcite compound (Alkamizer I of Kyowa Kagaku Co., Ltd.), (M = Mg, A
= CO ₃ , X = 0.3, m = 0.5) 5% by weight and a hindered amine compound (Tinuvin 622 from Ciba Geigy) 0.5% by weight were added to form a 100 μm thick film.

(2) Drop-free agent: (a) 70% by weight of colloidal silica (Catalyst Kasei's Cataloid SI-350) (b) Silane derivative: 5% by weight (γ-ureidopropyltriethoxysilane) (c) Nonionic surface activity Agent: 25% by weight (polyoxyethylene (7 mol) oleate) Water is added to the above-mentioned active ingredients (a) to (c), and the mixture is stirred and mixed. Agent.

On the other hand, for comparison, a film having a thickness of 100 μm based on LDPE (MI1.0, SG0.920) was coated with the above-mentioned non-dropping agent in the same manner as in Example 1 (hereinafter, “Film of Comparative Example 1”). ), Applicability and driplessness were evaluated.

As a result of the evaluation, it was coatability that the improvement effect was most clearly understood. That is, could not only coating about 2m ² to the base film with no drops in "Comparative Example 1 of Film" in 1 liter also coated about 6 m ² three times in the case of "film of Example 1" it Was completed. The time required for the spraying operation was about 45 minutes in the case of the “film of Comparative Example 1”, whereas the time required for the “film of Example 1” was about 15 minutes, which is one third.

When the drip-freeness after application was determined with the naked eye, "Comparative Example 1
In the “film”, application unevenness was observed everywhere, and there was a defective portion in a dripless manner. However, in the case of the “film of Example 1,” water droplets flowed down as a uniform water film.

(Example 2) The following base film was spread on a pipe house in the same manner as in Example 1, and the inner surface of the base film was coated with the non-droplet in the same manner as in Example 1, and the applicability and non-droplet properties of the non-droplet were evaluated. did.

(1) Base film: Thickness formed in the same manner as in Example 1 except that magnesium hydroxide was used instead of the hydrotalcite compound.
100μ film.

As a result of the evaluation, the coating area of the “film of Example 2” was approximately
4m ² , which took about 25 minutes. Further, although the driplessness was slightly inferior to that of Example 1, the water droplets flowed down as a substantially uniform water film.

(Examples 3 to 6) The following base film was spread on a pipe house in the same manner as in Example 1, and the inner surface thereof was coated with the non-droplet in the same manner as in Example 1. Was evaluated.

(1) Base film: A film having a three-layer structure shown in FIG. 2 and formed by blending the same hydrotalcite compound as used in Example 1 only in the intermediate layer m in an amount of 8% by weight. However, the thicknesses of the intermediate layer m and the transparent layers a and b are as shown in Table 1.

Table 2 shows the results of the evaluation.

As is apparent from Table 2, even when a transparent layer is interposed between the thermoplastic resin film containing the inorganic fine powder and the coating layer of the drip-free agent, the thickness of the transparent layer is 100 μ or less. Then, it can be seen that the adhesiveness of the drip-free agent coating layer and the effect of imparting drip-freeness to the resin film thereby can be achieved.

(Example 7) The base film (width 550 mm) of Example 1 was coated with the following drip-free agent at various speeds using a gravure coater having a roll width of 600 mm. The sex was evaluated. The drip-freeness was evaluated by setting a small extension stand in the field and extending the film on the stand. Note that the drip-free agent was dried with hot air.

(1) Drop-free agent A drop-free agent obtained by mixing the following active ingredients (a) to (d) in respective proportions.

(A) Polymer-A: 100 parts by weight (b) Alcohol-dispersed colloidal silica (methanol silica manufactured by Nissan Chemical Co., Ltd.): 35 parts by weight (c) Polyoxyethylene lauryl ether (surfactant): 15 parts by weight ( d) Methanol: 450 parts by weight However, the polymer-A in the above-mentioned active ingredient is prepared by reacting a mixed solution of the following components (a) to (d) at 60 ° C. for 5 hours, and adding NH ₃ 2
Compound neutralized with 0% aqueous solution.

(A) 2-hydroxyethyl acrylate: 99 parts by weight (b) Acrylic acid: 1 part by weight (c) Azobisisobutyronitrile (reaction catalyst): 0.5 part by weight (d) Methanol: 200 parts by weight For this purpose, the drip-free agent of Example 7 was applied to a 100 μm thick film based on LDPE (MI1.0, SG0.920),
In the same manner as in Example 7, coating was performed at various speeds (hereinafter, referred to as “film of Comparative Example 2”), and applicability and drip-freeness of the drip-free agent at each speed were evaluated.

Table 3 shows the results of visual observation during coating.
Shown in As for the drip-freeness, a film sample was prepared on November 26, 1988, spread on December 3, 1988, and visually observed on December 15, 1988. Table 4 shows the results.

As is clear from Tables 3 and 4, "Film of Comparative Example 2" can only take a coating speed of 5 to 10 m / min, while "Film of Example 7" has a speed of 40 to 50 m / min. It turns out that coating is possible.

〔The invention's effect〕

As described above, according to the present invention, since the above-described configuration is employed, it is excellent in applicability of the drip-free agent to the base film and drip-freeness after the application of the drip-free agent, and is inexpensive for agricultural use. A film can be obtained.

[Brief description of the drawings]

1, 2 and 3 are cross-sectional views of an agricultural film according to an embodiment of the present invention. F: Thermoplastic resin film D: Coating layer of drip-free agent a, b: Transparent layer m: Intermediate layer

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-56177 (JP, A) JP-A-57-98578 (JP, A) JP-A-52-69447 (JP, U) 31744 (JP, B2) JP-B 34-5890 (JP, B1)

Claims (4)

(57) [Claims] 1. A thermoplastic resin layer containing from 2.0 to 15% by weight of an inorganic fine powder and a thermoplastic resin layer containing from 0.1 to 2.0% by weight of an inorganic fine powder are laminated to improve the coating property of a drip-free agent. An agricultural film obtained by coating a coated thermoplastic resin film with a surface-applied drip-free agent containing an inorganic hydrophilic colloid substance and a hydrophilic organic compound as main components. 2. A thermoplastic resin layer containing 2.0 to 15% by weight of an inorganic fine powder, and 0.1 to 2.0% by weight of an inorganic fine powder on both surfaces.
A transparent resin-containing layer is laminated, and a thermoplastic resin film with improved application properties of the drip-free agent is coated with a surface-coated drip-free agent composed mainly of an inorganic hydrophilic colloidal substance and a hydrophilic organic compound. Agricultural film made. 3. The agricultural film according to claim 1, wherein the thickness of the transparent thermoplastic resin layer is 50 μm or less. 4. The agricultural film according to claim 1, wherein the thermoplastic resin is a polyolefin such as LDPE, EVA, or LLDPE.