JP5422173B2 - Agricultural coating - Google Patents

Description

  The present invention relates to an agricultural covering material for covering agricultural crops and the cultivation environment of agricultural crops.

  In facility cultivation (including house cultivation and tunnel cultivation) that promotes the growth of crops and the development of specific traits, a transparent resin film material (agricultural covering material) that covers the cultivation environment of crops and crops is used. As an agricultural covering material used in such institutional cultivation, a film made of vinyl chloride resin (PVC) has been used for a long time and is still widely used. Development and popularization of resin film (PO) is progressing.

  The main properties required for an agricultural covering material are anti-fogging property and anti-fogging durability in addition to transparency, weather resistance and strength. Antifogging is a property that allows the condensed water adhering to the inner surface of the coating material to flow down along the inner surface of the coating material without dropping it on the cultivated crop. The property does not deteriorate. Polyolefin resin films for agriculture cannot satisfy all of these properties with a single layer of a single material, so a multilayer structure is adopted, especially on the inner surface facing the crop side, with an anti-fogging agent composition A covering layer containing an object is formed.

In the prior art described in Patent Document 1 below, the base film is a film layer (A) made of an ethylene-vinyl acetate copolymer having a polyethylene or vinyl acetate content of less than 10% by weight, and a vinyl acetate content of 10 to 30% by weight. % Of an ethylene-vinyl acetate copolymer, and 0.1 to 30 parts by weight of an inorganic filler is blended in the film layer (A) or the film layer (B). It is disclosed that a coating layer derived from an antifogging agent composition containing silica gel and / or alumina sol as a main component and a hydrophobic thermoplastic resin as a binder component is formed on the surface of the film.
Japanese Patent Laid-Open No. 7-266518

  In this prior art, since each layer of the base film is formed of a single resin component, it is not possible to satisfy further properties required as a base film for agricultural coating materials. For example, there has been a problem that it is impossible to secure a necessary strength against an impact received by a collision object caused by a fall of a kite or a strong wind, and a sufficient weather resistance against bad weather cannot be obtained. In addition, since a high tear strength cannot be obtained, there is a problem that it is easy to tear at the corners of the blade or the framework of the facility.

  Furthermore, since the above-described base film of the prior art cannot obtain sufficient heat resistance, there is a problem that it is necessary to restrict use in an area where the midsummer daytime temperature is extremely high and heating in the facility. It was.

  Further, in the above-described prior art, since each layer is formed of a single resin component, it is necessary to increase the strength of each layer on the average when attempting to ensure the strength of the entire base film, and the antifogging agent composition It is necessary to ensure the strength of the layer on the side where the coating layer of the product is applied by making it a film layer made of an ethylene-vinyl acetate copolymer having a low vinyl acetate content. However, according to this, since the coating layer of the antifogging agent composition is formed on the relatively hard layer, the adhesion of the antifogging agent is low and the coating layer is liable to peel off, and it is used for a long period of 3 to 5 years However, there was a problem that good anti-fogging durability could not be secured.

  The present invention has been proposed in order to solve such problems of the prior art, and can increase impact strength to obtain high weather resistance against bad weather and high tear strength. High heat resistance can be obtained, and good anti-fogging sustainability can be ensured even for long-term use.

In order to achieve such an object, the present invention provides a protective film on the surface of the inner layer facing the agricultural product against a base film having a multilayer structure mainly composed of a polyolefin resin and having an inner layer, an intermediate layer, and an outer layer. An agricultural coating material in which a coating layer of a clouding agent composition is formed, wherein the inner layer is a resin layer mainly composed of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 30% by weight , The intermediate layer is a layer based on a mixed resin composed of many types of resin components including polyethylene, and the polyethylene included in the intermediate layer is a metallocene-catalyzed linear short chain branched polyethylene and a special metallocene catalyst linear It is characterized by being a short chain branched polyethylene. In the following description, “%” of vinyl acetate content indicates “% by weight”.

  By having such characteristics, the inner layer in which the coating layer of the antifogging agent composition is formed is a resin layer mainly composed of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 30%. Therefore, the adhesion with the antifogging agent can be increased by increasing the vinyl acetate flow rate and softening the inner layer. Thereby, the anti-fogging sustainability by the anti-fogging agent composition can be further increased, and high durability can be obtained by suppressing the deterioration of the anti-fogging property even for a long-term use of 3 to 5 years.

In addition, by making the intermediate layer a mixed resin layer made of different resin components, the strength reduction of the base film due to softening of the inner layer can be compensated for by improving the strength of the intermediate layer. In particular, by using polyethylene in the intermediate layer as metallocene-catalyzed linear short-chain branched polyethylene and special metallocene-catalyzed linear short-chain branched polyethylene, it is possible to ensure impact strength and tear strength in the intermediate layer, and to detect abnormalities such as wrinkles. Damage to weather and laceration can be reduced. Moreover, the functionality of the agricultural covering material can be further improved by mixing a resin material component having properties such as heat resistance as the intermediate layer.

  The present invention having such characteristics is an agricultural covering material using a polyolefin-based resin film as a base film, which can increase impact strength and obtain high weather resistance against bad weather, and can increase tear strength and tear. In addition, high heat resistance can be obtained, and good antifogging durability can be ensured even for long-term use.

  Embodiments of the present invention will be described below. An agricultural covering material according to an embodiment of the present invention has a multilayer structure including an inner layer, an intermediate layer, and an outer layer, and is formed on the surface of the inner layer on the side facing the crop with respect to a base film mainly composed of a polyolefin resin. A coating layer of the antifogging agent composition is formed. The base film may have a three-layer structure of an inner layer, an intermediate layer, and an outer layer, or may have a layer structure of four or more layers by forming the intermediate layer into a multilayer.

[Inner layer]
The inner layer is a soft layer that can enhance adhesion to the coating layer of the antifogging agent composition even at the expense of strength performance. Specifically, a resin layer mainly composed of an ethylene-vinyl acetate copolymer (EVA) having a high vinyl acetate (VA) content is employed. The content of vinyl acetate is not limited as long as sufficient adhesion can be obtained between the coating layer of the antifogging composition and excessive content should be avoided in consideration of the odor generation of vinyl acetate. The content is 10 to 30% based on the total weight. The resin component of the inner layer is mainly composed of an ethylene-vinyl acetate copolymer (EVA) having a high vinyl acetate (VA) content, but other resin components can be mixed. For example, an ethylene-vinyl acetate copolymer having a low vinyl acetate content (less than 10%, for example, 5%) can be mixed up to about 40% of the entire inner layer.

[About the middle layer]
The intermediate layer is a layer in which a sufficient strength can be obtained by mixing a plurality of types of resin components in order to supplement the strength sacrificed by the inner layer. Specifically, the base resin is a mixed resin composed of many types of resin components including polyethylene having excellent strength characteristics. In addition, by selecting a resin component that provides impact resistance, heat resistance, and the like, the intermediate layer is secured with various properties required as an agricultural covering material.

More specifically, the polyethylene contained in the intermediate layer is a metallocene-catalyzed linear short chain branched polyethylene (metallocene LL) and a special metallocene-catalyzed linear short chain branched polyethylene (special metallocene LL). Metallocene LL is a linear short-chain branched polyethylene (LLDPE) polymerized with a metallocene catalyst, and is a copolymer of ethylene and an α-olefin such as 1-butene, 1-hexene, 1-octene, and the like. Depending on the type of polymerization and the type of short chain branch (α-olefin), ethylene branch, n-butyl branch, and n-hexyl branch are respectively introduced into low density polyethylene. Metallocene LL is superior to ordinary low density polyethylene (LDPE) and EVA in terms of cold resistance and impact resistance, and has excellent overall properties in terms of tearing, tension, puncture strength, pinhole resistance, etc. ing.

Special metallocene LL has a melt tension of 3.0 to 9.0 cN, a tensile impact strength of 800 KJ / m ^{2 to} 1300 KJ / m ² , and a dart impact strength of 30 KJ / m / 50 μm to 100 KJ when forming a 50 μm thick film. This refers to a metallocene-catalyzed linear short-chain branched polyethylene having a strength of / m / 50 μm. This special metallocene LL corresponds to CB0002 of Exelen (registered trademark), a polyethylene product of Sumitomo Chemical Co., Ltd. CB0002 has a large tensile impact strength of 1160 KJ / m and a large dart impact strength of 90 MPa / 50 μm.

  In addition, EVA is included in one of the resin components of the intermediate layer. EVA is a resin material that is highly flexible and excellent in weather resistance, chemical resistance, and transparency. By including EVA in the resin component of the intermediate layer, the adhesion between the inner layer and the intermediate layer is improved. Moreover, inflation moldability improves by including EVA.

  As what is selected as a resin component of an intermediate | middle layer, an ethylene-methyl methacrylate copolymer (EMMA) can be mentioned. This EMMA is a resin material having properties equivalent to those of EVA and excellent in heat resistance.

  Moreover, further special performance can be added by including an inorganic filler in the intermediate layer. For example, hydrotalcite, calcium, magnesium, aluminum and other oxides, hydroxides, carbonates, silicates and their composites are blended in an amount of about 20% by weight in order to improve heat retention.

(Example of blending ratio of intermediate layer)
Examples of the blending ratio of the intermediate layer include 40% to 60% by weight of EVA for supporting workability, and 40% to 20% by weight of metallocene LL for supporting strength and workability. The special metallocene LL that plays the role of supporting the impact strength is contained in an amount of 10% by weight to 20% by weight, and the inorganic filler that plays the role of holding the heat retaining property is contained by 5% by weight to 15% by weight. By using such a blending ratio, excellent characteristics in both processability and impact strength can be obtained.

  The metallocene LL has a melt tension of 2.0 cN or less and can be thinned. However, the dart impact strength of metallocene LL is 20 KJ / m or less. For this reason, in order to raise the dirt impact strength of the intermediate layer 12, it is necessary to mix a special metallocene LL having a high dirt impact strength. Since the special metallocene LL has a melt tension of 3.0 to 9.0 cN, the ratio is small as described above with respect to the total weight of the intermediate layer 12.

  Various conventional polyethylenes tend to have low moldability when the impact strength is high and low impact strength when the moldability is high. Metallocene LL has extremely high impact strength but low molding processability. Therefore, it is used by mixing with EVA excellent in moldability. As the EVA mixed in the intermediate layer, one having a low vinyl acetate content is employed in order to secure a desired strength. For example, a vinyl acetate content of 15% or less is preferred. The special metallocene LL of the present invention corresponds to CB0002 (model number) in Exelen (registered trademark) GMH manufactured by Sumitomo Chemical Co., Ltd. Special metallocene LL has high impact strength and excellent moldability.

  Since the special metallocene LL has a high melt tension, it is not possible to increase the proportion of the total amount of the mixed resin constituting the intermediate layer. Then, when mixing special metallocene LL, the mixture ratio is limited to 10%-20%. In the case of metallocene LL, since the melt tension is low, the ratio of the mixed resin constituting the intermediate layer to the total amount can be increased. Therefore, in one example, the blending ratio of the metallocene LL is limited to 40% to 20% as a relative mixing ratio with the blending ratio of 40% to 60% of the ethylene-vinyl acetate copolymer resin. Special metallocene LL is excellent in both extrusion load and melt tension, has good melt fluidity, and has an extruded surface that is extremely smooth and less susceptible to rough skin.

  Further, EMMA (for example, MMA content 15%) can be adopted instead of the EVA blending in the above-described example, and an agricultural covering material having properties equivalent to EVA can be obtained.

[Outer layer]
The outer layer can be a film layer made of a metallocene-catalyzed linear short chain branched polyethylene (LLDPE polymerized with a metallocene catalyst: metallocene LL). The reason for selecting metallocene LL as the outer layer is that metallocene LL has high transparency, it is difficult to block, it is not necessary to use an anti-blocking powder during inflation molding, and a long-life anti-fogging film can be formed by coating. This is because there are characteristics. In addition, as described above, metallocene LL is superior in cold resistance and impact resistance compared to LDPE and EVA, and has comprehensively superior performance in terms of tearing, tension, puncture strength, pinhole resistance, etc. Have This is because the metallocene LL has a melt tension of 2.0 cN or less and can be thinned.

[About anti-fogging agent coating layer]
As the coating layer of the antifogging agent composition formed on the surface of the inner layer described above, a known layer can be employed. For example, silica sol and / or alumina sol is used as a main component, and a silica or alumina binder component is mixed therein. As the binder component, a hydrophobic thermoplastic resin can be used, and examples thereof include acrylic resins, vinyl chloride-vinyl acetate resins, polyethylene resins, vinyl chloride resins, vinylidene chloride resins, and unsaturated polyester resins. be able to. Preferable examples include those containing colloidal silica as a main component and a hydrophobic acrylic resin as a binder component.

[Production method]
The base film is formed into a multilayer structure by inflation molding, and trimmed in a state where the inner layer is folded down toward both outer sides to obtain two base films. On the other hand, a coating layer of the antifogging agent composition is formed on the exposed surface of the inner layer. The coating layer is formed by a known method (doctor blade coating method, roll coating method, dip coating method, spray coating method, rod coating method, bar code method, knife coating method). Apply by brushing etc.) and then dry. Various additives (ultraviolet absorbers, light stabilizers, antioxidants, lubricants, heat stabilizers, colorants, antifogging agents, antistatic agents, etc.) are usually added to each resin layer as required when forming the base film. It can be made to mix | blend in the quantity.

[Example]
As an example of the present invention, a coating layer of an antifogging agent composition is formed on the inner layer surface of a three-layer base film having an outer layer thickness of 30 μm, an intermediate layer thickness of 90 μm, and an inner layer thickness of 30 μm. An example is shown in Table 1. As the antifogging agent, one having colloidal silica as a main component and a hydrophobic acrylic resin as a binder component was used. A small amount of an antioxidant and a light stabilizer were added to each of the outer layer, the intermediate layer, and the inner layer. As an example, as an antioxidant, a combination of phenol and phosphorus is about 0.05 to 0.2%, an ultraviolet absorber is used as a light stabilizer, and benzophenone and benzotriazole are each 0.05 to 1%. About 0.1 to 1% of hindered amines can be added.

  In the examples (Examples 1 to 6), the inner layer was made of a resin layer mainly composed of EVA having a VA content of 15%, so that the inner layer was softened and the adhesion with the antifogging agent could be improved. Compared with the case where EVA having a VA content of 5% is employed in the inner layer as in the comparative examples (Examples 7 and 8), the adhesion of the antifogging agent is clearly improved. I was able to get sex.

  Moreover, in an Example (Example 1-Example 6), sufficient intensity | strength was able to be ensured as the whole agricultural coating | covering material by making an intermediate | middle layer into a mixed resin component. In particular, Examples (Examples 1 to 6) in which 20% of metallocene LL was contained as a resin component and 20% of special metallocene LL were contained could also provide an equivalent agricultural covering material.

  Further, in Examples (Examples 4 and 6) in which EMMA (MMA 15%) was used instead of EVA as a resin component, high heat resistance could be obtained.

In Table 1, “Anti-fogging sustainability” refers to the anti-fogging property of an agricultural covering material after one year of house extension, ◎: Flow of water drops is very good, ○: Flow of water drops is good, △: Flow of water drops Is bad, x: Evaluation was made such that water droplets do not flow. “Impact resistance” was evaluated by the test method of JIS K 714-1 after one year of house extension, and evaluated as follows: ： １: 1300 or more, ◯: 1200 or more, Δ: 1200 or less. The greater the impact strength, the less tearing from the crease. Tendency is that creases are less likely to occur at 1300 and above in JIS K 7124-1, and creases are produced at 1200 and above, but there is almost no break from the folds. It is in.

Claims (4)

Agricultural coating material in which a coating layer of an antifogging agent composition is formed on the surface of the inner layer on the side facing the crop against a base film having a multilayer structure having a polyolefin resin as a main component and having an inner layer, an intermediate layer, and an outer layer. Because
The inner layer is a resin layer mainly composed of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 30% by weight ,
The intermediate layer is a layer based on a mixed resin composed of many kinds of resin components including polyethylene,
The polyethylene contained in the intermediate layer is a metallocene-catalyzed linear short-chain branched polyethylene and a film thickness of 50 μm, a melt tension of 3.0 to 9.0 cN, and a tensile impact strength of 800 KJ / m ^{2 to} 1300 KJ / Agricultural coating material characterized by being a special metallocene-catalyzed linear short chain branched polyethylene having a m ² and a dart impact strength of 30 KJ / m / 50 μm thickness to 100 KJ / m / 50 μm thickness .   2. The agricultural covering material according to claim 1, wherein the intermediate layer contains an ethylene-vinyl acetate copolymer as a resin component. The intermediate layer, agricultural covering material according to any one of claims 1 or 2, characterized in that it comprises an inorganic filler. The agricultural coating material according to any one of claims 1 to 3 , wherein the outer layer is made of a metallocene-catalyzed linear short-chain branched polyethylene.