JPH0466187B2 - - 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, transparency, antifogging properties, and workability. (Prior art) With the modernization of agricultural crop cultivation in recent years, facility cultivation,
For example, greenhouse cultivation and tunnel cultivation have become 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,
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 has poor heat retention 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 combined with silica (Japanese Patent Publication No. 47-13853) and magnesium compounds (Japanese Patent Publication No. 59-226037).
Addition of fillers such as hydrotalcite (JP 60-104141), water-absorbing resin (JP 61-81446)
or addition of ethylene-vinyl alcohol copolymer resin (Japanese Unexamined Patent Publication No. 118941/1983). 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 retention, and working strength. The inventors of the present invention sought to improve upon these drawbacks, and as a result of extensive research in search of an agricultural multilayer film with particularly excellent transparency, heat retention, antifogging properties, and work strength, the inventors found that each layer contains a specific filler and droplet agent. The present invention was completed based on the discovery that the object could be achieved by using a film having a specific multilayer structure. (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 (A) contains 0.1 to 2% by weight of an antifogging agent and has a vinyl acetate content of 10 to 20% in which the content of hydrotalcite or its green compound is 3 or less based on the weight ratio of the antifogging agent. % by weight of an ethylene-vinyl acetate copolymer layer; (B) an ethylene resin layer containing 1 to 40% by weight of hydrotalcite or its similar greening compound; and the layer (A) is a multilayer film. It is characterized by having a structure of three or more layers, with layer (B) existing as an intermediate layer of a multilayer film in the inner layer of the film. Ethylene constituting the inner layer (A) layer in the present invention
The vinyl acetate copolymer is a copolymer with a vinyl acetate content of 10 to 20% by weight. Such a copolymer is produced by reacting ethylene and vinyl acetate through a high-pressure radical polymerization process, and has an MFR of 0.5 to 10, preferably 0.5 to 5. If the MFR is too small, the film's formability, especially extrusion processability, and high-speed stretchability will deteriorate, which is undesirable.
A large value is not preferable because it causes instability of the film's formability, especially bubbles in inflation molding. The vinyl acetate content of the ethylene-vinyl acetate copolymer resin used is preferably 10 to 20% by weight, and 10 to 20% by weight.
If it is less than %, the antifogging properties will deteriorate, which is not preferable. On the other hand, if it exceeds 20%, antifogging properties and heat resistance will deteriorate, which is not preferable. 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 this category include polyoxyalkylene ethers, partial esters of polyhydric alcohols, partial esters of alxylene oxide adducts of polyhydric alcohols,
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 sobutitan monolaurate, polyoxyethylene sorbitan mono Valmitate, glycerin monolaurate, glycerin monobalmitate,
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 ethylene-vinyl acetate copolymer resin. If it is less than 0.1% by weight, the anti-fogging properties will deteriorate, which is not preferable. If it exceeds 2% 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 layer (B), may be added to this ethylene-vinyl acetate copolymer resin layer, but the amount added is preferably 3 or less based on the weight 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 intermediate layer (B) in the present invention is 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. Low-density polyethylene with a density of less than 0.930, ethylene-vinyl acetate copolymer, ethylene-alkyl (meth)acrylate copolymer, etc. are manufactured by a high-pressure radical process, and their MFR is 0.5 to 10.
Preferably, those having a value of 0.5 to 5 are used. If MFR is too small, film formability, especially extrusion processability,
This is not preferred because high-speed stretchability deteriorates. or
A large MFR is undesirable because it causes unstable film moldability, especially bubbles in inflation molding. Among polymers produced by high-pressure radical polymerization processes, ethylene-vinyl acetate copolymers with a vinyl acetate content of 3 to 45%, especially 10 to 20% by weight, are the most preferred in terms of transparency, heat retention, price, etc. . 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. When the average particle size exceeds 10 μm, the strength and transparency of the film are significantly reduced, 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 alcohols, titanate coupling agents, silane coupling agents, and the like. The amount of hydrotalcite to be used is appropriately selected such that ethylene resin/hydrotalcite=99 to 60/1 to 40 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 emitting the agricultural film at night will be insufficient. That is, heat retention becomes insufficient. On the other hand, if the amount exceeds the above-mentioned range and is too large, the decrease in transparency becomes large 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. Preferably, this layer contains an antifogging agent. This antifogging agent has the role of preventing the antifogging agent in the inner layer from migrating to the outer layer through the intermediate layer during film expansion, resulting in dilution of the antifogging agent concentration in the inner layer, or to prevent the antifogging agent on the surface of the inner layer from becoming diluted. It plays the role of replenishing the anti-fog agent when it is washed away by water droplets and the anti-fog performance deteriorates in a short period of time. Therefore, its concentration is not particularly specified, but it is generally 0.1 to 2% by weight as in the inner layer.
It is preferable to contain. 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. The film of the present invention is used as a multilayer film consisting of three or more layers consisting of an inner layer (A), an intermediate layer (B), and at least an outer layer (C). The resins constituting the outer layer (C) include the ethylene resins described for the intermediate layer (B), such as low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-alkyl (meth)acrylate copolymer, and ethylene-α. -Olefin copolymers and the like can be used. Of course, the multilayer film of the present invention has these (A)/(B)/
Not limited to the three-layer structure shown in (C), but also (1) inner layer (A)/middle layer (B)/middle layer (D)/outer layer (C) (2) inner layer (A)/middle layer (D) / Middle layer (B) / Outer layer (C) (3) Inner layer (A) / Middle layer (D) / Middle layer (B) / Middle layer (D) / Outer layer (C) (4) Inner layer (A) )/intermediate layer (D)/intermediate layer (B)/intermediate layer (E)/outer layer (C), etc. It is also used as a multilayer film with four or more layers. As the resin used for each layer other than the inner layer (A) layer, intermediate layer (B) layer, and outer layer (C) layer, various ethylene-based resins explained for the intermediate layer (B) layer can be appropriately selected and used. . Hydrotalcite and an antifogging agent can be added to these layers as necessary. Generally, hydrotalcite contained in the surface layer (C) roughens the surface, so its concentration should be 40% or less, preferably
It is preferably 25% or less. On the other hand, the middle class (D)
In the case of (E) layer, etc., the amount of hydrotalcite to be added can be arbitrarily selected as there is no restriction in terms of surface roughening, but in general
Less than 40%. The antifogging agent may be appropriately selected from the various antifogging agents described for the inner layer (A). Moreover, there is no particular restriction on its concentration. 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 is not only a transparent film, but also 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 0.03, which is the sum of the thickness of the intermediate layer and (A) layer.
The thickness ratio of each layer can be arbitrarily selected as long as mm or more is satisfied. (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) Considering the antifogging performance, an ethylene-vinyl acetate copolymer containing 10 to 20% by weight of vinyl acetate is optimal as the resin used for layer (A). (2) When hydrotalcite is added to the (A) layer containing an antifogging agent, the antifogging agent is adsorbed or miscible with the hydrotalcite, and as a result, migration of the antifogging agent to the film surface is suppressed. It was discovered that the antifogging properties were insufficient. Therefore, it is preferable that the layer (A) does not contain hydrotalcite.
However, if it is absolutely necessary to add hydrotalcite to improve heat retention, the weight of hydrotalcite added must be kept at 3 or less relative to 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. However, in terms of transparency, the limit should be 40%, preferably 25%. 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 hydrotalcite added to the inner layer (A) and the intermediate layer (B) and the concentration ratio with the antifogging agent. The agricultural multilayer film of the present invention has excellent heat retention, 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 to stand in a cold air circulation room at 10°C, and after 20 hours, it was returned to room temperature and left to stand for 4 hours. This cycle was repeated 7 times. The film was rated 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) Dust resistance A laminated film was stretched for 4 months in a tunnel created for the measurement of heat retention described below. ) was determined based on the reduction rate. 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) Heat retention This laminated film was spread in an airtight manner on an arch-shaped construction to create a tunnel. 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. (5) Strength at break The strength at break of the laminated film in the MD direction and the TD direction was measured by a tensile test (based on JIS K 6783). (6) 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. (7) Falling ball impact strength Measured in accordance with ASTM D 1709A method. (8) Film Stiffness Film stiffness was measured using a Handle-C-Meter. (9) 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. A multilayer film for agricultural use containing hydrotalcite or a related compound thereof and an antifogging agent, wherein the multilayer film contains (A) 0.1 to 2% by weight of an antifogging agent and (B) an ethylene-vinyl acetate copolymer layer with a vinyl acetate content of 10 to 20% by weight, in which the content of Cyto or its analogous compound is 3 or less based on the weight ratio of the antifogging agent; an ethylene-based resin layer containing hydrotalcite or its analogous compound; and a structure of three or more layers in which layer (A) is an inner layer of the multilayer film and layer (B) is an intermediate layer of the multilayer film. A multilayer film for agricultural use that is characterized by: