JP5367605B2 - Agricultural polyolefin resin film and method for producing the same - Google Patents

Description

  The present invention relates to an agricultural polyolefin resin film excellent in transparency and tear strength of a crease and a method for producing the same.

  Greenhouses and tunnels used in house cultivation and tunnel cultivation are made by coating a flexible resin film on a framework such as a metal pipe. Transparency and heat retention are typical performances required for resin films used for greenhouse coatings. Conventionally, soft films made of vinyl chloride resin have been widely used as both of them.

  However, in recent years, coating materials are rapidly replacing vinyl chloride resin films with polyolefin resin films with many improved performances. The polyolefin resin is a homopolymer or copolymer of an α-olefin (for example, ethylene or propylene) having a double bond at the end of the molecule. Specifically, a low density polyethylene resin, a linear low density polyethylene resin, an ethylene-vinyl acetate copolymer (EVA), or the like is used.

  The main reasons for replacing vinyl chloride resin film with polyolefin resin film are lightness of film, improvement of weather resistance, and improvement of heat resistance due to development of heat insulation agent, etc. because it does not contain plasticizer. Yes, the performance is not inferior to that of vinyl chloride resin films.

  Resin films as agricultural coating materials are required to have good tear strength, impact strength, tensile strength, etc., moldability, high transparency, and excellent weather resistance, antifogging properties, etc. The Therefore, a three-layer agricultural polyolefin system using linear low-density polyethylene resin polymerized with a strong metallocene catalyst for the inner and outer layers, and EVA and low-density polyethylene resin excellent in flexibility for the intermediate layer A resin film has been proposed (Patent Document 1).

Japanese Patent Laid-Open No. 11-254612

  However, the agricultural polyolefin-based resin film shown in Patent Document 1 uses linear low-density polyethylene resin excellent in strength for the inner layer and the outer layer, but the intermediate layer occupying 80% of the thickness is only EVA. Or it is the structure which is only LDPE and the intensity | strength as the whole film is insufficient. In particular, when a wide film is wound around a core to form a roll, the film is folded in half at the center in the width direction or double-rolled with the tubular film folded flat, and the end in the width direction is doubled. Although it is common to use a folded gusset winding, the strength of the crease at that time is too weak, and there is a problem that it is easy to tear along the line of the original crease after being covered with the framework.

  The present invention has been devised in view of the above-mentioned problems, and performs an inflation molding process that is excellent in transparency, has a very high tear strength when the film is wound twice, and has excellent workability and stability. An object of the present invention is to provide an agricultural polyolefin-based resin film that can be used.

The agricultural polyolefin-based resin film of the present invention is composed of three layers of an outer layer, an intermediate layer, and an inner layer of an olefin-based resin film. In the agricultural olefin-based resin film formed by forming an antifogging coating on the inner layer,
The outer layer has a low density polyethylene polymerized by a high pressure method having a density of 0.910 to 0.930 g / cm ³ and / or a density of 0.910 to 0.930 g / cm ³ and a melt tension at 190 ° C. of 4. A layer composed of linear low density polyethylene polymerized with a metallocene catalyst of 0 to 9.0 cN,
The intermediate layer is a layer mainly composed of an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 10 to 20% by mass,
The inner layer is a layer made of linear low-density polyethylene having a density of 0.910 to 0.930 g / cm ³ and a melt tension at 190 ° C. of 0.5 to 3.0 cN,
And the ratio of the thickness with respect to the whole film of the said outer layer, an intermediate | middle layer, and an inner layer is 10-25% of outer layers, 30-50% of intermediate layers, 35-50% of inner layers,
The polyolefin resin film for agriculture, wherein an antifogging coating film comprising a resin emulsion and silica sol and / or alumina sol is formed on the inner layer.

In addition, the method for producing an agricultural polyolefin resin film of the present invention is an agricultural olefin system in which a tubular film is produced by inflation molding and an antifogging coating film is formed on the outside of the tubular film folded flat. In the method for producing a resin film,
The inner layer of the cylindrical resin film is a low density polyethylene polymerized by a high pressure method having a density of 0.910 to 0.930 g / cm ³ and / or a density of 0.910 to 0.930 g / cm ³ and 190 An outer layer made of linear low-density polyethylene polymerized with a metallocene catalyst having a melt tension at 4.0 ° C. of 4.0 to 9.0 cN,
The intermediate layer of the cylindrical resin film is an intermediate layer mainly composed of an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 10 to 20% by mass,
The outer layer of the cylindrical resin film is an inner layer made of linear low-density polyethylene having a density of 0.910 to 0.930 g / cm ³ and a melt tension at 190 ° C. of 0.5 to 3.0 cN. ,
In addition, the tubular film is subjected to inflation molding so that the ratio of the thickness of the outer layer, the intermediate layer, and the inner layer to the entire film is 10 to 25% of the outer layer, 30 to 50% of the intermediate layer, and 35 to 50% of the inner layer.
Folding the tubular film flat,
Forming an anti-fogging coating film comprising a resin emulsion and silica sol and / or alumina sol on the inner layer surface forming the outer layer of the folded tubular film;
After the anti-fogging coating film is formed, the tubular resin film folded in a flat shape is cut into one end in the width direction or wound into a double winding without being cut. A method for producing an agricultural polyolefin resin film. This one end may be cut after winding.

  Furthermore, in the method for producing an agricultural polyolefin resin film of the present invention, the intermediate layer has an ethylene-vinyl acetate copolymer resin content of 60 to 98% by mass with a vinyl acetate content of 10 to 20% by mass, and the resin film is recycled. It consists of 2-40 mass% of materials, It is a manufacturing method of the polyolefin resin film for agriculture characterized by the above-mentioned.

  According to the present invention, as a whole film, the transparency and the tear strength of the double fold crease are extremely high, have excellent processability, and can be stably blown by an agricultural polyolefin resin film and its A manufacturing method can be provided.

  Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited to these embodiments.

  The agricultural polyolefin resin film of the first embodiment is composed of a three-layer film of an outer layer, an intermediate layer, and an inner layer. And an anti-fogging coating film is formed in an inner layer.

  The outer layer is formed as an inner layer of the cylindrical resin film when the cylindrical resin film is formed by inflation molding.

The outer layer includes low density polyethylene (LDPE) polymerized by a high pressure method having a density of 0.910 to 0.930 g / cm ³ and / or a density of 0.910 to 0.930 g / cm ³ and a melt tension at 190 ° C. Is a layer made of a linear low density polyethylene (special LLDPE) polymerized with a metallocene catalyst having a C of 3.5 to 8.0 cN. LDPE and special LLDPE used for this layer have a high melt tension at 190 ° C. of 3.5 to 8.0 cN, and therefore have good inflation moldability and high extrusion fluidity. When used for the inner layer of the film, it was found that transparency can be secured because it can be processed at low temperature. The ratio of the thickness of the outer layer to the entire film is 10 to 25%. If this ratio is less than 10%, the moldability by inflation molding is lowered, and if it exceeds 25%, the tear strength of the double-folded crease portion is lowered, which is not preferable.

  As the LDPE, commercially available products can be used as appropriate, and examples thereof include “NUC8505” and “NUC8160” manufactured by Dow Chemical, “LD176R” manufactured by Tosoh, and “LF423M” manufactured by Nippon Polyethylene.

  As the special LLDPE, a commercially available product can be used as appropriate, and examples thereof include “Excellen GH051”, “Excellen GH030”, and “Sumikasen GT-140”, which are polyethylene products of Sumitomo Chemical Co., Ltd.

  The intermediate layer is a layer mainly composed of an ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content of 10 to 20% by mass. Moreover, the same kind of film that is out of specification can be recycled as a raw material. When the recycled material is blended in the intermediate layer, it is preferably blended so as to be 40% by mass or less, more preferably 35% by mass or less of the entire resin component constituting the intermediate layer. If the amount of the recycled material is 40% by mass or less, there is little influence on the strength and transparency of the resin film. As this recycled material, it is preferable to use a material obtained by pulverizing the produced film and then extruding it into a pellet. By pelletizing, it is possible to make the raw material uniform and to remove foreign matters such as dust adhering to the original film.

  The ratio of the thickness of the intermediate layer to the entire film is 30 to 50%. If this ratio is less than 30%, the flexibility is lowered, and if it exceeds 50%, the tensile strength is lowered, the film becomes thin when strongly pulled during stretching, and the deterioration of the film is accelerated.

  As the EVA, commercially available products can be used as appropriate. For example, “NUC3230” and “NUC3224” manufactured by Dow Chemical Company, “Ultrasen 630” manufactured by Tosoh, “V115” manufactured by Ube Maruzen Polyethylene, V215 "and the like.

  Moreover, it is preferable to mix | blend an inorganic filler with an intermediate | middle layer. Examples of the inorganic filler include hydrotalcite, oxides such as calcium, magnesium, and aluminum, hydroxides, carbonates, silicates, and oxides, hydroxides, and carbonates of the plurality of metals described above. , Silicates, and complex compounds thereof can be used as appropriate. The inorganic filler is preferably added in an amount of 5 to 15 parts by mass, more preferably 7 to 12 parts by mass, per 100 parts by mass of the resin component constituting the intermediate layer. If the blending amount of the inorganic filler is 5 parts by mass or more per 100 parts by mass of the resin component, the heat retention can be sufficiently improved, and if it is 15 parts by mass or less, transparency can be ensured.

  The inner layer is formed as an outer layer of the cylindrical resin film when the cylindrical resin film is formed by inflation molding.

The inner layer is a layer made of linear low density polyethylene (LLDPE) having a density of 0.910 to 0.930 g / cm ³ and a melt tension at 190 ° C. of 0.5 to 3.0 cN. The ratio of the thickness of the inner layer to the entire film is 35 to 50%. When this ratio is less than 35%, the tensile strength and the tear strength of the crease are lowered, and when it exceeds 50%, the flexibility is lowered, the adhesion to the framework of the cultivation greenhouse is worsened, and the workability of the spreading is worsened. Therefore, it is not preferable.

  As the LLDPE, commercially available products can be used as appropriate. For example, “moretech 0138NK”, “moretech 0218CN”, “evolution SP1520”, “evolution SP2020” made by Prime Polymer, “Umerit 1520F” made by Nippon Polyethylene ”,“ UF320 ”,“ UF240 ”and the like made by Ube Maruzen polyethylene.

  The antifogging coating film is formed on the surface of the inner layer. The anti-fogging coating film comprises a resin emulsion and silica sol and / or alumina sol. By forming the anti-fogging coating film, it is possible to prevent water droplets generated on the surface of the film inner layer due to a difference in temperature between the inside and outside of the film from dropping into the inside of the greenhouse, etc., when the greenhouse is coated.

  Further, each of the layers may contain a resin component other than those described above without departing from the object of the present invention.

  In addition, layers other than the above layers can be provided without departing from the object of the present invention. In that case, it may be provided between the inner layer and the outer layer.

  Moreover, various additives mix | blended with the polyolefin-type resin film for agriculture can be mix | blended with each layer. Examples thereof include ultraviolet absorbers such as benzophenone and benzotriazole, hindered amine light stabilizers, antioxidants, colorants, heat insulating materials, antiblocking agents, slip agents, and antistatic agents.

  The agricultural polyolefin resin film of the present invention has a thickness of 50 to 250 μm. When the thickness of the polyolefin resin film for agriculture is 100 μm, for example, when the outer layer is 40 μm, the intermediate layer is 40 μm, and the outer layer is 20 μm, the transparency and the tear strength of the folds are high, and the inflation molding can be performed well. .

  Next, the manufacturing method of the polyolefin-type resin film for agriculture of this invention is demonstrated. Each pellet composed of the resin composition of each layer containing the above resin and additives is supplied to each extruder of a three-layer inflation molding machine, and the molten resin laminated and extruded from the multilayer die is subjected to inflation molding to form a cylinder A resin film is produced. Next, the cylindrical resin film is folded flat. Furthermore, an anti-fogging coating film is formed on both outer surfaces of the folded cylindrical resin film. Furthermore, an agricultural polyolefin resin film can be produced by cutting one end in the width direction of a cylindrical resin film folded flat or winding it in a double winding without cutting. .

  In inflation molding, by using not only the three-layer inflation molding machine as described above, but also using four or more inflation molding machines, by introducing the same resin composition into a plurality of extruders for forming adjacent layers, A three-layer agricultural polyolefin resin film can also be produced.

  In the step of folding the cylindrical resin film flat, for example, it passes between guide rolls arranged so as to gradually sandwich the cylindrical resin film, and finally is folded flat between the pair of pinch rolls. It can be set as a resin film.

  In the process of forming the antifogging coating film, an antifogging coating comprising a resin emulsion and silica sol and / or alumina sol is applied to a doctor blade coating method, a roll coating method, a dip coating method, a spray coating method, a rod coating method, a bar coating method, A known coating method such as knife coating or brush coating may be employed and dried after coating. As a drying method after coating, either natural drying or forced drying may be employed. When the forced drying method is employed, drying may be performed in a temperature range of 40 to 150 ° C., preferably 50 to 80 ° C. . In consideration of drying speed and stability, it is advantageous to adopt the hot air drying method.

  Moreover, before forming an anti-fogging coating film, both the outer surfaces of the folded cylindrical resin film can also be surface-treated. By surface-treating both outer surfaces of the folded cylindrical resin film, the adhesion between the resin film and the antifogging coating film is improved. Examples of the surface treatment include corona discharge treatment, plasma discharge treatment, glow discharge treatment, and primer treatment.

  When one end in the width direction of the cylindrical resin film folded flat is cut and wound, a cutter blade, a round blade, or the like can be used, and cut along the transport direction of the resin film. The place to cut may be a crease part of a cylindrical resin film folded flat, or may be cut so as to cut off a part near the crease. When the vicinity of the crease is cut off, the two sheets can be cut simultaneously or sequentially one by one. If the cutting positions are staggered, a clue for spreading the folded resin film can be used, which is a preferable method.

Hereinafter, the present invention will be described in more detail with reference to examples. Evaluation items and evaluation criteria in the examples were performed as follows.
(transparency)
Three samples are taken from each of the three-layer agricultural polyolefin-based resin films produced according to the examples, and the HAZE value is measured using a HAZE meter (manufactured by Nippon Denshoku Co., Ltd.). evaluated.
○: Less than 13 Δ: 13 or more, less than 15 ×: 15 or more

(Tear strength of crease)
Five samples of the fold portion of the double-wrapped three-layer agricultural polyolefin-based resin film manufactured according to the example were taken, and a 2 cm notch was added to the fold portion. The tear strength of the sample was measured and the average value was evaluated according to the following criteria.
○: 7N or more Δ: 5N or more, less than 7N ×: less than 5N

Resins used in Examples and Comparative Examples are as follows.
LLDPE: manufactured by Prime Polymer Co., Ltd., “Moretech 0138NK”, linear low-density polyethylene based on metallocene catalyst, density 0.916 g / cm ³ , MFR 1.52 g / 10 min (230 ° C., 21.2 N), melt tension: 3. 0 cN
LDPE: manufactured by Dow Chemical Co., Ltd., “NUC-8160”, high-pressure low-density polyethylene, density 0.923 g / cm ³ , MFR 2.4 g / 10 min (230 ° C., 21.2 N), melt tension 5.0 cN
Special LLDPE: manufactured by Sumitomo Chemical Co., Ltd., “Excellen GH030”, linear low-density polyethylene based on metallocene catalyst, density 0.912 g / cm ³ , MFR 0.5 g / 10 min (230 ° C., 21.2 N), melt tension 4cN
EVA: “NUC-3224” manufactured by Dow Chemical Company, ethylene-vinyl acetate copolymer, vinyl acetate content 15% by mass, density 0.940 g / cm ³ , MFR 1.5 g / 10 min (230 ° C., 21.2 N ), Melt tension 9.4 cN
Recycled material: the film of Example 1 crushed and pelletized

  The melt tension is determined by measuring the stress when the molten polymer is stretched at a constant speed. For the measurement, a capillograph with a melt tension measurement attachment manufactured by Toyo Seiki Seisakusho was used. The conditions were a resin temperature of 190 ° C., a melting time of 6 minutes, a barrel diameter of 9.55 mmφ, an extrusion speed of 15 mm / min, a winding speed of 10 to 20 m / min, a nozzle diameter of 2.095 mmφ, and a nozzle length of 8 mm.

[Example 1]
100 parts by mass of LDPE as an outer layer, 100 parts by mass of EVA as an intermediate layer, and 100 parts by mass of LLDPE as an inner layer are supplied to each extruder of a three-layer inflation molding machine, and the melted resin that is laminated and extruded from a multilayer die is subjected to inflation molding. A 100 μm cylindrical resin film was produced. Next, the cylindrical resin film is folded flat, then both sides of the flat folded cylindrical resin film are corona discharge treated, antifogging paint is applied by dip coating, and excess antifogging paint is removed with a wire bar. Then, after drying in a hot air drying oven, an antifogging coating film having a solid content of 1 g / m ² is formed, and then one end in the width direction of the cylindrical resin film folded flat is cut. Agricultural polyolefin-based resin films were produced by winding them into heavy rolls. Table 1 shows the thickness and resin composition of each layer (all numerical values indicate the resin component of each layer in mass%), and the results of each evaluation, that is, the crease tear strength and transparency.

[Examples 2 and 3 and Comparative Examples 1 to 5]
Except for changing the thickness and resin composition of each layer as described in Table 1, the three-layered cylindrical resin film with anti-fogging coating film of Examples 2 and 3 and Comparative Examples 1 to 5 was used in the same manner as in Example 1. Manufactured. The evaluation results are shown in Table 1.

  The anti-fogging paint is composed of 50 parts by mass of silica sol (Nissan Chemical Co., Ltd., “Snow Tech 20”, 20% concentration) and acrylic modified urethane resin emulsion (Adeka Co., Ltd., “HUX-401”, 20% concentration). A mixture obtained by mixing 40 parts by mass, 1 part by mass of a silicone-based surfactant (manufactured by Toray Dow Corning, “FZ-77”), and 90 parts by mass of water was used.

  Moreover, Examples 1-3 and Comparative Examples 1-5 are phenol, phosphorus antioxidant (product made from Ciba Specialty Chemicals) with respect to 100 mass parts of resin components also in any layer structure resin film of a three-layer structure. , IRGANOX B921), 0.1 part by weight of light stabilizer (manufactured by Ciba Specialty Chemicals, TINUVIN 783) and 0.5 part by weight of UV absorber (manufactured by Sipro Kasei, SEESORB102) In the intermediate layer, 10 parts by mass of hydrotalcite (manufactured by Kyowa Chemical Co., Ltd., DHT-4A) was blended.

  As shown in Table 1, all of the examples have good crease tear strength and transparency, but in the comparative examples, either the crease tear strength or transparency is poor. The agricultural polyolefin-based resin film of the present invention is extremely useful as an agricultural resin film used for facility cultivation.

  The agricultural polyolefin-based resin film of the present invention has high transparency, stable inflation moldability, high crease tear strength, and other properties required for agricultural films as a whole. It is useful as an agricultural polyolefin resin film having excellent strength, tensile strength, weather resistance, anti-fogging property, heat retention and the like. Moreover, the agricultural polyolefin-type resin film which has the above-mentioned outstanding performance can be provided by the manufacturing method of the polyolefin-type resin film for agriculture of this invention.

Claims (3)

Agricultural olefin resin film comprising an outer layer, an intermediate layer and an inner layer of three olefin resin films, wherein an antifogging coating film is formed on the inner layer,
The outer layer has a low density polyethylene polymerized by a high pressure method having a density of 0.910 to 0.930 g / cm ³ and / or a density of 0.910 to 0.930 g / cm ³ and a melt tension at 190 ° C. of 4. A layer composed of linear low density polyethylene polymerized with a metallocene catalyst of 0 to 9.0 cN,
The intermediate layer is a layer mainly composed of an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 10 to 20% by mass,
The inner layer is a layer made of linear low-density polyethylene having a density of 0.910 to 0.930 g / cm ³ and a melt tension at 190 ° C. of 0.5 to 3.0 cN,
And the ratio of the thickness with respect to the whole film of the said outer layer, an intermediate | middle layer, and an inner layer is 10-25% of outer layers, 30-50% of intermediate layers, 35-50% of inner layers,
Agricultural polyolefin resin film characterized in that an anti-fogging coating film comprising a resin emulsion and silica sol and / or alumina sol is formed on the inner layer In the method for producing an agricultural olefin resin film in which a tubular film is produced by inflation molding and an antifogging coating film is formed on the outside of the tubular film folded flat,
The inner layer of the cylindrical resin film is a low density polyethylene polymerized by a high pressure method having a density of 0.910 to 0.930 g / cm ³ and / or a density of 0.910 to 0.930 g / cm ³ and 190 An outer layer made of linear low-density polyethylene polymerized with a metallocene catalyst having a melt tension at 4.0 ° C. of 4.0 to 9.0 cN,
The intermediate layer of the cylindrical resin film is an intermediate layer mainly composed of an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 10 to 20% by mass,
The outer layer of the cylindrical resin film is an inner layer made of linear low-density polyethylene having a density of 0.910 to 0.930 g / cm ³ and a melt tension at 190 ° C. of 0.5 to 3.0 cN. ,
In addition, the tubular film is subjected to inflation molding so that the ratio of the thickness of the outer layer, the intermediate layer, and the inner layer to the entire film is 10 to 25% of the outer layer, 30 to 50% of the intermediate layer, and 35 to 50% of the inner layer.
Folding the tubular film flat,
Forming an anti-fogging coating film comprising a resin emulsion and silica sol and / or alumina sol on the inner layer surface forming the outer layer of the folded tubular film;
After the anti-fogging coating film is formed, the tubular resin film folded in a flat shape is cut into one end in the width direction or wound into a double winding without being cut. Of manufacturing polyolefin resin film for agriculture   The said intermediate | middle layer consists of 60-98 mass% of ethylene-vinyl acetate copolymer resin of vinyl acetate content 10-20 mass%, and 2-40 mass% of the recycled materials of the resin film of Claim 2 characterized by the above-mentioned. The manufacturing method of the polyolefin-type resin film for agriculture of Claim 2 to do.