JPH0465780B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of 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] 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 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 solve 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 a magnesium compound (Japanese Patent Publication No. 13853-1983).
226037), Hydrotalcite (Unexamined Japanese Patent Publication 1986-
104141), a water-absorbing resin (Japanese Patent Application Laid-Open No. 61-81446), and an ethylene-vinyl allyl copolymer resin (Japanese Patent Application Laid-open No. 118941-1982). Further, JP-A No. 57-160638 discloses a film in which a polyolefin layer containing a water drop preventive agent 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 agent 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, antifogging properties, 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 problem] Accordingly, the present invention relates to an agricultural multilayer film, and the present invention relates to an agricultural multilayer film containing hydrotalcite or a related compound thereof and an antifogging agent. The film contains (A) 2 to 40% by weight of hydrotalcite or its related compounds, and the content of the antifogging agent is 0.3 or less by weight relative to the hydrotalcite or its related compounds; a polymeric resin layer; (B) a vinyl acetate content of 10 to 2% by weight of an antifogging agent, and the content of hydrotalcite or a related compound thereof is 3 or less based on the weight ratio of the antifogging agent; 20% by weight of an ethylene-vinyl acetate copolymer layer, and the layers (A) and (B) are present on the surface of the multilayer film. In the present invention, the ethylene-α-olefin copolymer resin constituting one of the outer layers (A) is a combination of ethylene and α-olefin such as propylene, butene-1, hexene-1, 4-methylpentene-1, and octene. It is a copolymer of Such copolymers are prepared in the presence of a catalyst containing a transition metal compound (so-called Ziegler process), a chromium oxide medium supported on alumina or silica-alumina (Phillips process), a molybdenum oxide catalyst supported on alumina (standard process), etc. , manufactured in liquid phase or gas phase, melt flow rate (hereinafter referred to as MFR)
The unit (g/10min) is 0.5 to 20, preferably 0.5 to 10, and the density is preferably 0.940g/ ^cm3 or less.
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. From the viewpoint of moldability, surface properties, etc., high-pressure polyethylene, ethylene-vinyl acetate copolymer resin, etc. may be blended. (A) What is hydrotalcite or its analogous compound added to layer (hereinafter abbreviated as hydrotalcite) M ²⁺ _1-x Al _x (OH) ₂ (A ^n- ) _x/o・mH ₂ O... (1) In the formula, M ²⁺ represents a divalent metal ion selected from the group consisting of Mg, Ca, and Zn, A _o- represents an n-valent anion, and x and m meet the conditions of the following formula. It is a compound, a fired product thereof, etc. that satisfies the following: 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 Alkamizer 1 (x = 0.33, m = 0.5, A = CO ₃ ^2- ) from Kyowa Scientific Industry Co., Ltd.;
Alcamizer 2 (x=0.33, m=0, A=CO ₃ ^2
− ) 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 used is ethylene-α-
Olefin copolymer resin/hydrotalcites =
The amount is appropriately selected from 98 to 60/2 to 40 parts by weight. More preferably, the ratio is 98-75/2-25. If the amount exceeds the above-mentioned range and is too small, the so-called infrared absorbing ability will be lowered 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 and is too large, the transparency will be greatly reduced and the visible light transmittance will be reduced. As a result, the transmission of sunlight energy through the agricultural film during the day is reduced, making it difficult for the soil temperature inside the greenhouse to rise, resulting in a decrease in 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. Although it is basically preferable that this (A) layer does not contain an antifogging agent, it may be added as long as the antifogging agent/hydrotalcite ratio is 0.3 or less, preferably 0.1 or less. If this value is exceeded, the antifogging agent will easily bleed out to the outer surface layer of the film, resulting in whitening of the film and significant surface contamination due to outdoor dust and sand adhesion, which will eventually reduce the visible light transmittance of the film. This is undesirable because it reduces the transmission of solar energy through the agricultural film during the day. In the present invention, the ethylene-vinyl acetate copolymer constituting one of the other outer layers (B) has a vinyl acetate content of
It is a 10-20% by weight copolymer. Such copolymers are produced by reacting ethylene and vinyl acetate through a high-pressure radical polymerization process, and their MFR
is 0.5 to 10, preferably 0.5 to 5. 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. 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.
% or less, it is not preferable because the antifogging property deteriorates. 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 outer 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 monopanemitate, 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 these, nonionic surfactants whose main components are esters of fatty acids having 14 to 22 carbon atoms and polyhydric alcohols such as sorbitan, sorbitol, glycerin, polyglycerin, pumepylene glycol, or alkylene oxide adducts thereof are preferred. It is mentioned as. 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 antifogging 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. The ethylene-vinyl acetate copolymer resin layer must satisfy a thickness of 30μ or more. If the thickness is smaller than this, the antifogging property will be poor. Hydrotalcite may be added to this ethylene-vinyl acetate copolymer resin 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 agricultural multilayer film of the present invention can also be used as a two-layer film in which both layers (A) and (B) are laminated. 3
It is also possible to use the film as a multilayer film. As the resin used for the intermediate layer, various polyolefin resins widely used in this field, such as polyethylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, and polypropylene, can be selected as appropriate. . Of course, it is also possible to blend the burrs of the multilayer film of the present invention and reuse it. Further, this layer may contain hydrotalcite and an antifogging agent as required. In general, the filler contained in the surface layer has the function of roughening the film surface, so it is desirable that the filler concentration be low.
For this reason, it is more preferable to include a large amount of filler in the intermediate layer. For example, ethylene-α-olefin copolymer or/and vinyl acetate content is 10%
An example of the method is to provide the following ethylene-vinyl acetate copolymer resin with a layer containing 5% or more of hydrotalcite as an intermediate 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 that the sum of the thickness of the intermediate layer and (B) is 0.03mm.
As long as the above conditions are satisfied, the thickness ratio of each layer can be arbitrarily selected. Furthermore, when the agricultural multilayer film of the present invention is used for lining plastic houses, tunnels, curtains, etc., it is usually used with the (A) layer on the outside and the (B) layer on the inside. [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) The resin used for layer (A) is ethylene-
α-olefin copolymers are optimal. (2) Hydrotalcite, an infrared absorbing agent added to layer (A), 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 appearance and transparency, it improves by 40%,
Preferably the limit should be 25%. Generally, when it is necessary to increase the amount added to improve heat retention, if it is not possible to increase the amount of hydrotalcite in layer (A) from the viewpoint of appearance and transparency, an intermediate layer is provided. It is useful to add hydrotalcite to. (3) Although it is preferable that the (A) layer does not contain an antifogging agent from the viewpoint of antifogging agent bleed-out, the (B) layer,
When adding the antifogging agent in the intermediate layer to prevent it from migrating to layer (A) due to a concentration gradient and reducing the antifogging effect on the surface of layer (B), the weight of the antifogging agent added is The amount should be less than 0.3 of the weight of hydrotalcite. (4) As the resin used for layer (B), an ethylene-vinyl acetate copolymer containing 10 to 20% by weight of vinyl acetate is optimal in consideration of antifogging performance. (5) When hydrotalcite is added to the layer (B) containing an antifogging agent, the antifogging agent is adsorbed or miscible with the hydrotalcite, and as a result, the migration of the antifogging agent to the film surface is suppressed. It was found that the anti-fogging properties were insufficient. Therefore, it is preferable that the layer (B) does not contain hydrotalcite. However, if it is absolutely necessary to add hydrotalcite to improve heat retention, the weight of hydrotalcite added should be 3 times the weight of the antifogging agent.
It is necessary to keep the following in mind. Based on the above experimental results, the present inventors have developed the present invention by specifying the film structure and the type and concentration ratio of the additives added to both outer layers (A) and (B). completed. 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 it exceeds the gist thereof. Examples 1 to 3 Comparative Examples 1 to 9 A 150 mm three-layer die (manufactured by Tomy Machinery Co., Ltd.) was used as a three-layer inflation molding device, and a 40 mm extruder (manufactured by Modern Machinery Co., Ltd.) was used for the outer layer. ), a 45 mm extruder (manufactured by Placo Co., Ltd.) for the middle layer and a 50 mm extruder (manufactured by Modern Machinery Co., Ltd.) for the inner layer, molding temperature 160 ° C, blow ratio.
1.5 and a take-up speed of 5 m/min, multilayer or single-layer films having the configurations shown in Table 1 were 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 Seal the top of a thermal container (diameter 15 cm, height 17 cm) filled with 25°C water to 2/3 of the container capacity with the sample, and place it in a -10°C cold air circulation type cold room. After 20 hours, the mixture was returned to room temperature and left to stand for 4 hours. This cycle was repeated 7 times. 10 for completely transparent and no clouding
The evaluation was made on a scale of 10 to 1, with 1 being the case where the film was 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 a luminometer (manufactured by Tokyo Kohden Co., Ltd., Model ANA 300). 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 between the inside and outside of a house at a height of 20 cm from the ground surface was measured every 10 minutes (January 1985, 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 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 D1709 Method A. (8) Film Stiffness Film stiffness was measured using a Handle-O-Meter. (9) Tensile strength of laminated film according to JIS K 6783.
The tensile strength in MD 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 a related compound thereof and an antifogging agent, wherein the multilayer film contains (A) 2 to 40% by weight of hydrotalcite or a related compound thereof; and (B) an ethylene-α olefin copolymer resin layer in which the content of an antifogging agent is 0.3 or less by weight relative to hydrotalcite or its related compounds; an ethylene-vinyl acetate copolymer layer having a vinyl acetate content of 10 to 20% by weight, in which the content of hydrotalcite or its related compounds is 3 or less based on the weight ratio of the antifogging agent; ) and (B) are present on the surface of the multilayer film. 2. The agricultural multilayer film according to claim 1, wherein the layer (A) is an outer layer and the layer (B) is an inner layer.