JPH0466185B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a multilayer film for agricultural use, and more particularly, to a multilayer film for agricultural use that has excellent heat retention, heat-resistant fusion properties, transparency, antifogging properties, and workability. be. (Prior Art) In recent years, with the modernization of agricultural crop cultivation, facility cultivation, such as greenhouse cultivation and tunnel cultivation, has come to be widely practiced. In these cultivations, polyethylene film, polyvinyl chloride film, and ethylene-vinyl acetate copolymer resin film are used as primary covering materials for plastic houses and tunnels, and as secondary covering materials for linings such as curtains. There are various other resin films, but among them, soft polyvinyl chloride film is currently the mainstream coating material because it has excellent heat retention, transparency, work strength, etc., and is also inexpensive. However, polyvinyl chloride film has problems in its disposal itself, such as generation of halogen gas and low combustibility. In addition, the surface of this film is generally sticky due to bleed-out of the plasticizer, and when used outdoors for a long period of time, dust and the like adhere to it, resulting in a decrease in light transmittance, making it difficult to use it for a long period of time. On the other hand, the alternative ethylene-vinyl acetate copolymer resin film is inferior in heat retention, heat fusion resistance, and working strength compared to polyvinyl chloride film, and therefore has limitations in its usage conditions. Furthermore, polyethylene film is inferior to polyvinyl chloride film in heat retention, antifogging properties, and transparency, so its use has been limited. In order to overcome these drawbacks, various methods have recently been proposed to improve the heat retention properties and workability of ethylene-vinyl acetate copolymer resins. For example, to improve heat retention, ethylene-vinyl acetate copolymer resin is mixed with silica (Japanese Patent Publication No. 47-13853) and magnesium compounds (Japanese Patent Application Laid-open No. 59-226037).
Publication) Hydrotalcite (Japanese Patent Application Laid-open No. 1983-104141
These methods include adding a filler such as JP-A-61-81446) or an ethylene-vinyl alcohol copolymer resin (JP-A-55-118941). Further, JP-A No. 57-160638 discloses a film in which a polyolefin layer containing a water drop preventive material and a polyolefin layer containing a metal-containing organic compound are laminated, and JP-A No. 58-160146 discloses a film in which a polyolefin layer containing a water drop prevention material and a polyolefin layer containing a metal-containing organic compound are laminated, and JP-A No. 58-160146 discloses a film in which a polyolefin layer containing a water drop preventive material and a polyolefin layer containing a metal-containing organic compound are laminated. City polyethylene (hereinafter L-
An agricultural film is disclosed in which a base material layer mainly composed of LDPE (sometimes abbreviated as LDPE) and a resin layer containing a surfactant are layered. However, it has been found that these laminated films have not yet achieved the level of improved heat retention required by the market. That is, with conventional means, it has been difficult to obtain a film that satisfies all of transparency, heat fusion resistance, heat retention, and working strength. In order to improve these drawbacks, the present inventors
An effective multilayer film for agriculture has an ethylene resin layer containing hydrotalcite and an ethylene-vinyl acetate copolymer layer containing 10 to 20% by weight of vinyl acetate containing an antifogging agent on the surface of the multilayer film. He discovered something and filed a patent application (Japanese Patent Application No. 61-262017, etc.). However, as a result of further investigation, we found that if the film of the invention was used in a particular way, for example, during the day, the film could be rolled up and exposed to direct sunlight for a long period of time to ventilate the greenhouse for the purpose of temperature control. During this process, it was discovered that the film caused heat fusion, which caused problems in practical use. In order to solve this problem, it has been found that it is effective to use low-density polyethylene or an ethylene-vinyl acetate copolymer containing less than 10% by weight of vinyl acetate in the inner layer. (Means and Effects for Solving the Problems) Therefore, the present invention relates to an agricultural multilayer film containing hydrotalcite or its green compound and an antifogging agent. The multilayer film is made of (A) low-density polyethylene as an inner layer, which contains 0.1 to 2% by weight of an antifogging agent, and in which the content of hydrotalcite or its similar green compound is 3 or less based on the weight ratio of the antifogging agent; Containing a layer of ethylene-vinyl acetate copolymer having a vinyl acetate content of less than 10% by weight, and as a layer other than the inner layer, (B) an ethylene resin containing 1 to 60% by weight of hydrotalcite or its green compound; The present invention is an agricultural multilayer film characterized by comprising a layer. In the present invention, the polymer constituting the inner layer (A) layer is:
Low-density polyethylene or ethylene-vinyl acetate copolymer with a vinyl acetate content of less than 10% by weight. Low-density polyethylene refers to polyethylene with a density of less than 0.930 g/cm ³ . Such low density polyethylene is roughly classified into branched low density polyethylene and linear low density polyethylene. Branched low density polyethylene is produced by reacting ethylene or ethylene with small amounts of comonomers in the presence of peroxides through a high pressure radical polymerization reaction process. Linear low density polyethylene is composed of ethylene and α-
A catalyst containing an olefin with a transition metal compound (so-called Ziegler process), a chromium oxide catalyst supported on alumina or silica-alumina (Phillips process),
It is produced in the liquid or gas phase in the presence of a molybdenum oxide catalyst supported on alumina (standard method). These low density polyethylenes have a density of 0.930g/ ^cm3
If it is less than 0.930 g/cm ³ , transparency deteriorates, which is not preferable. Ethylene-vinyl acetate copolymers containing less than 10% by weight of vinyl acetate are produced by reacting ethylene and vinyl acetate in the presence of peroxide by a high-pressure radical polymerization process. Vinyl acetate content is 10
If the amount is less than 10% by weight, the heat-resistant fusion bonding properties will deteriorate, which is not preferable. MFR of these polymers is 0.5-10 preferably 0.5
~5. If the MFR is too small, the film's formability, especially extrusion workability, and high-speed stretching properties will deteriorate, which is undesirable.If the MFR becomes too large, the film's formability, especially bubble instability during inflation molding, will be undesirable. For the inner layer, one of these polymers can be selected and used, but if the final average vinyl acetate content is less than 10% by weight, two or more polymers can be blended. It can also be used as
Furthermore, various polyolefin resins, rubbers, etc. may be added as long as the function as an inner layer is not impaired. As the antifogging agent added to this inner layer, various antifogging agents well known in this technical field can be used. For example, nonionic, anionic, and cationic surfactants are used. Compounds that fall under these categories include polyoxyalkylene ether,
Partial ester of polyhydric alcohol, partial ester of alkylene oxide adduct of polyhydric alcohol,
Examples include higher alcohol sulfate ester alkali metal salts, alkylaryl sulfonates, quaternary ammonium salts, and fatty acid amine derivatives. Specifically, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene nonyl phenyl ether, polyethylene glycol monopalmitate, polyethylene glycol monostearate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate. tate, glycerin monolaurate, glycerin monopalmitate,
Glycerin monostearate, glycerin monooleate, pentaerythritol monolaurate,
Sorbitan monopalmitate, sorbitan monobehenate, sorbitan distearate, diglycerin monooleate, triglycerin diolate,
Sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium butylnaphthalene sulfonate, cetyltrimethylammonium chloride, alkyldimethylbenzylammonium chloride, dodecylamine hydrochloride, laurylamide ethyl laurate phosphate, triethylcetylammonium iodide, oleyl aminodiethylamine Examples include basic pyridinium salts such as hydrochloride and dodecylpyridinium sulfate. Among them, nonionic surfactants whose main components are esters of fatty acids having 14 to 22 carbon atoms and polyhydric alcohols such as sorbitan, glycerin, polyglycerin, propylene glycol, or alkylene oxide adducts thereof are preferred. Can be mentioned. Although it is possible to select and use one type of these antifogging agents, it is recommended to use two or more types of antifogging agents in order to simultaneously satisfy initial droplet flow properties, droplet persistence, low temperature droplet flow properties, etc. It can also be used as a blend. The content of the antifogging agent is appropriately selected within the range of 0.1 to 2% by weight based on the polymer constituting the layer (A). If it is less than 0.1% by weight, the anti-fogging properties will deteriorate, which is not preferable. 2
If it exceeds % by weight, it is not preferable because the heat resistance decreases and the film becomes noticeably whitened when used in spring when the temperature rises. (A) Layer must satisfy 30μ or more. If the thickness is smaller than this, the antifogging property will be poor. Hydrotalcite, which will be described in detail in the (B) layer, may be added to this (A) layer, but the amount added is preferably 3 or less based on the weight ratio of the antifogging agent. If it exceeds this range, the antifogging properties will be significantly reduced and the film will not be suitable for use as an agricultural film. The ethylene resin constituting the layer (B) in the present invention is high-pressure low-density polyethylene with a density of less than 0.930,
Ethylene-vinyl acetate copolymer, ethylene-alkyl (meth)acrylate copolymer, ethylene-
α-olefin copolymers and the like. Of course, these resins can be used alone or in combination of two or more. High-pressure low-density polyethylene with a density of less than 0.930,
Ethylene-vinyl acetate copolymers, ethylene-alkyl (meth)acrylate copolymers, etc. are manufactured by high-pressure radical processes, and their MFR is 0.5.
-10, preferably 0.5-5 is used.
If the MFR is too small, the film's formability, especially extrusion workability, and high-speed stretchability will deteriorate, which is undesirable. Furthermore, if the MFR becomes large, the film's moldability becomes unstable, especially bubbles in inflation molding, which is undesirable. Among polymers produced by high-pressure radical polymerization processes, ethylene-vinyl acetate copolymers with a vinyl acetate content of 45% by weight or less, especially 20% by weight or less, are preferred due to their transparency, heat retention, heat fusion resistance, price, etc. Most preferable in this respect. Ethylene-α-olefin copolymer is ethylene, propylene, butene-1, hexene-1,4-
It is a copolymer with α-olefins such as methylpentene-1 and octene, and this copolymer is prepared using a catalyst containing a transition metal compound (the so-called Ziegler method), a chromium oxide catalyst supported on alumina or silica-alumina (Philips It is produced by copolymerization in the liquid or gas phase in the presence of a molybdenum oxide catalyst supported on alumina (standard method), and the melt flow rate (hereinafter abbreviated as MFR, unit: g/10min) is 0.5-20, preferably
0.5~10, density preferably below 0.940g/ ^cm3
It is 0.935g/ ^cm3 or less. If the MFR is too low, the film's formability, particularly its extrusion processability and high-speed stretchability, will deteriorate, which is not preferable. Furthermore, if the MFR increases, the mechanical strength decreases, which is not preferable. If the density is too high, transparency will be lost, which is not preferable. If the density is too low, the elasticity will become weak and the spreading workability will be poor, which is not preferable. What is hydrotalcite or its similar green compound added to layer (B) (hereinafter abbreviated as hydrotalcite) (M ²⁺ ) _1-x Al _x (OH) ₂ (A ^n- ) _x/o・mH ₂ O...(1) However, in the formula, M ²⁺ represents a divalent metal ion selected from the group consisting of Mg, Ca and Z _o , A ^n- represents an n-valent anion, and x and m are the following: It is a compound, a fired product thereof, etc. that satisfies the conditions of the formula and is represented by 0<x<0.5 0≦m≦2. Examples of n-valent anions represented by A ^n- in the above formula (1) include Cl ^- , Br ^- , I ^- , NO ₃ ^- , ClO ₄ ^- ,
SO ₄ ^2- , CO ₃ ^2- , SiO ₃ ^2- , HPO ₄ ^2- , HBO ₃ ^2- ,
Examples include anions such as PO ₄ ^2- . Specific examples include Alcamizer 1 (x=0.33, m=0, A=CO ₃ ^2- ) and Alcamizer 2 (x=0.33, m=0, A=CO ₃ ^2- ) from Kyowa Chemical Industry Co., Ltd. ) etc. The average particle diameter is preferably 10 μm or less, and more preferably 3 μm or less. If the average particle size exceeds 10μ, the strength and transparency of the film will drop significantly, making it difficult to use it as an agricultural film. In order to improve the dispersibility of the hydrotalcite, it is preferable to use it after treatment with a surface treatment agent. Examples of surface treatment agents include paraffin, fatty acids, higher alcohols,
Polyhydric alcohol, titanate coupling agent,
Examples include silane coupling agents. The amount of hydrotalcite to be used is appropriately selected such that ethylene resin/hydrotalcite=99 to 40/1 to 60 parts by weight. More preferably, the ratio is 98
~75/2~25 used. If the amount deviates from the above range and is too small, the so-called infrared absorbing ability will be reduced and the ability to prevent infrared rays from transmitting and radiating through the agricultural film at night will become insufficient. That is, heat retention becomes insufficient. On the other hand, if the amount exceeds the above range, the dispersion of the resin and hydrotalcite will be insufficient.
The decrease in transparency increases and the visible light transmittance decreases. As a result, the transmission of sunlight energy through the agricultural film during the day is reduced, so the soil temperature inside the greenhouse is not raised, which ultimately reduces the amount of energy required for crop growth, resulting in poor growth. In addition to this decrease in transparency, the mechanical strength of the film also decreases, making it more likely to tear and reducing the workability of stretching. This layer can contain an antifogging agent.
This anti-fog agent is an anti-fog agent in the inner layer during film expansion.
The function is to prevent the antifogging agent from migrating to the outer layer and resulting in diluting the concentration of the antifogging agent in the inner layer, or when the antifogging agent on the surface of the inner layer is washed away by water droplets, reducing the antifogging performance in a short period of time. It plays the role of replenishing the drug. Therefore, its concentration is not particularly limited, but it is generally preferable to contain it in an amount of 0.1 to 2% by weight as in the inner layer. Further, the antifogging agent used may be the same as that for the inner layer, or may be different from that for the inner layer, for example, a slow-acting antifogging agent may be used. However, if layer (B) is present in the outer layer and is used for the exterior lining of a house, it is preferable that layer (B) does not contain an antifogging agent, but the antifogging agent/hydrotalcite It may be added as long as the ratio is 0.3 or less, preferably 0.1 or less. If this value is exceeded, the antifog agent will bleed out to the outer surface of the film, causing whitening of the film and contamination due to outdoor dust and sand, and ultimately reducing the visible light transmittance of the film. This is undesirable because it reduces the transmission of sunlight energy through the agricultural film during the day. The film of the present invention has (1) inner layer (A)/outer layer (B) (2) inner layer (A)/intermediate layer (B)/outer layer (C) (3) inner layer (A)/intermediate layer (C)/outer layer (B) (4) Inner layer (A) / Middle layer (B) / Middle layer (D) / Outer layer (C) (5) Inner layer (A) / Middle layer (D) / Middle layer (B) / Outer layer (C) ) (6) Inner layer (A) / Middle layer (D) / Middle layer (B) / Middle layer (D) / Outer layer (C) (7) Inner layer (A) / Middle layer (D) / Middle layer (B) It can be used as various multilayer films with two or more layers such as / intermediate layer (E) / outer layer (C). The resin used for each layer other than layer (A) and layer (B) is
(B) The ethylene resin described for layer, i.e., low density polyethylene, ethylene-vinyl acetate copolymer,
Ethylene-alkyl (meth)acrylate copolymers, ethylene-α-olefin copolymers, etc. can be used. Hydrotalcite and an antifogging agent can be added to these layers as necessary. Note that the concentration of hydrotalcite is 60% or less for the above-mentioned reasons. The antifogging agent may be appropriately selected from the various antifogging agents described for the inner layer (A). The burrs and the like of the multilayer film of the present invention do not prevent the use of the multilayer film by adding it to each layer. Each layer having the above structure may contain various other additives commonly used in this technical field, if necessary. Examples of such other additives include antioxidants,
Mention may be made of various additives well known in this technical field, such as light stabilizers, ultraviolet absorbers, antistatic agents, lubricants, antiblocking agents, and antifogging agents. The agricultural film of the present invention can be formed not only as a colorless film but also as a film colored with pigments, dyes, etc. The film of the present invention is formed by an inflation method, a casting method, etc., and its total thickness is in the range of 0.035 to 0.3 mm, preferably in the range of 0.05 to 0.2 mm, considering strength, performance, production cost, etc. . Also, the ratio of the thickness of each layer is that the sum of the thicknesses of layer (A) and layer (B) is 0.03mm.
As long as the above conditions are satisfied, the thickness ratio of each layer can be arbitrarily selected. (Effects of the Invention) The present inventors have studied a method of producing an agricultural thermal insulation film that is superior to a flexible polyvinyl chloride film using an ethylene polymer. As a result, we found the following. (1) As the resin used for layer (A), in consideration of heat-resistant fusion performance, low-density polyethylene or an ethylene-vinyl acetate copolymer with a vinyl acetate content of less than 10% by weight is optimal. (2) On the other hand, in these polymers, the antifogging agent has a relatively large migration property, so when hydrotalcite is added to this layer, the antifogging agent is adsorbed or dissolved in the hydrotalcite, so that it does not transfer to the film surface. The migration of antifogging agents tends to be suppressed. In this way, a small amount of hydrotalcite may be added to layer (A) for the purpose of adjusting the migration speed of the antifogging agent and improving heat retention, but when using any polymer, It is necessary to keep the weight of hydrotalcite added to 3 or less based on the weight of the antifogging agent. (3) The resin used for layer (B) can be appropriately selected from ethylene resins, taking into consideration strength, scratch resistance, workability in spreading, filler retention ability, etc. (4) Hydrotalcite, an infrared absorbing agent added to layer (B), has an excellent infrared absorption effect and is one of the best additives for heat-retaining agricultural films, and its heat-retaining effect increases as the amount of addition increases. It improves over time. Based on the above experimental results, the present inventors identified the raw material resin that constitutes the film, and
The present invention was completed by specifying the amount of antifogging agent added to the inner layer (A) and layer (B), the amount of hydrotalcite, and the concentration ratio of the two. The agricultural multilayer film of the present invention has excellent heat retention, heat fusion resistance, transparency, antifogging properties, and working strength, and is superior to polyvinyl chloride film in terms of stain resistance and disposal. Therefore, it is extremely useful as a covering film for greenhouse cultivation. (Examples) Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited to the following examples unless the gist thereof is exceeded. Examples 1 to 4 Comparative Examples 1 to 7 As a three-layer inflation molding device, a three-layer die with a diameter of 150 mm (manufactured by Tomy Machinery Co., Ltd.) was used, and an extruder used a 40 mm diameter extruder (manufactured by Modern Machinery Co., Ltd.) for the outer layer. ),
The middle layer was made using a 45 mmφ extruder (manufactured by Plako Co., Ltd.), and the inner layer was made using a 50 mm diameter extruder.
mmφ extruder (manufactured by Modern Machinery Co., Ltd.) at a molding temperature of 160℃, a blow ratio of 1.5, and a take-off speed of 5m/min.
A multilayer or single layer film having the structure shown in Table 1 was obtained. Note that a commercially available soft polyvinyl chloride film was used. The following evaluation tests were conducted on each film. The results are shown in Table 1. (1) Anti-fogging properties at low temperatures The top of a thermal container (diameter 15 cm, height 17 cm) filled with 25°C water to 2/3 of the container capacity was sealed with a sample.
It was left standing in a cold air circulation room at 10°C, and after 20 hours, the temperature was returned to room temperature and left standing for 4 hours. This cycle was repeated 7 times. The evaluation was made on a scale of 10, with 10 being completely transparent and no fogging at all, and 1 being completely cloudy due to condensed water droplets. (2) Anti-fog durability A sample film was stretched at an angle of 5° from the horizontal on a constant temperature water bath kept at 50°C, and the state of water condensation on the film's inner surface was observed over time. It was evaluated on a 10-point scale in the same way as the anti-fog property. (3) Anti-fogging property A laminated film was stretched for 4 months in a tunnel created for the measurement of heat retention described below. Judgment was made based on the reduction rate relative to the The sunlight transmittance was measured using an illuminance meter (manufactured by Tokyo Kohden Co., Ltd.,
ANA 300 model). A-3% or less, B-3 to 10%, C-10% or more (4) Fusion temperature The inner surfaces of the films are overlapped and irradiated with infrared rays. A thermocouple is set on the opposite side of the film to the infrared ray irradiation surface and its temperature is measured. The adhesive strength between the inner surfaces of the film after irradiation is measured. 20g/20mm
The temperature corresponding to the width is defined as the fusion temperature. Adhesive strength measurement conditions were 23℃ and crosshead speed 300.
It was done at mm/min. (5) Heat retention A tunnel was created by spreading this laminated film in a sealed manner on an arch-shaped construction body. The arch-shaped structure was approximately 0.65m high and 1.5m wide. The difference in temperature inside and outside the house at a height of 20 cm from the ground
Measurements were taken every 10 minutes (January 1985, located in Ichihara City, Chiba Prefecture) and the average was calculated for 7 days from 6:00 pm to 6:00 the next morning. The results are shown in Table 1. (6) Strength at break The strength at break in the MD direction and TD direction of the laminated film was measured by a tensile test (based on JIS K 6783). (7) Elongation at break Similar to the method for measuring strength at break, elongation of laminated film is
The elongation at break in the MD and TD directions was measured. (8) Falling ball impact strength Measured in accordance with ASTM D 1709A method. (9) Film Stiffness Film stiffness was measured using a Handle-C-Meter. (10) Tensile strength MD of laminated film according to JIS K 6783
The tensile strength in the direction and TD direction was measured. The results are shown in Table 1.

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Claims (1)

[Scope of Claims] 1. An agricultural multilayer film containing hydrotalcite or its related compound and an antifogging agent, wherein the multilayer film contains (A) 0.1 to 2% by weight of an antifogging agent as an inner layer. The inner layer contains a layer of low-density polyethylene in which the content of hydrotalcite or a related compound thereof is 3 or less based on the weight ratio of the antifogging agent, or an ethylene-vinyl acetate copolymer having a vinyl acetate content of less than 10% by weight. An agricultural multilayer film characterized in that the other layers include (B) an ethylene resin layer containing 1 to 60% by weight of hydrotalcite or an analogous compound thereof.