JPS63149147A - Agricultural multilayer film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] 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. It is something.

[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. Polyethylene films,
Polyvinyl chloride film, ethylene-vinyl acetate cofj
There are synthetic resin films and 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 the generation of halodane gas and its low combustibility.

In addition, the surface of this film generally becomes sticky due to plasticizer bleed-out, and when used outdoors for a long period of time, dust etc. adhere to the surface, reducing light transmittance, making it difficult to use for a long period of time. .

On the other hand, an alternative ethylene-vinyl acetate copolymer resin film has poor heat retention and working strength compared to polyvinyl chloride film, and therefore has limitations in terms of use.

Furthermore, polyethylene film is inferior in heat retention, antifogging properties, and transparency compared to polyvinyl chloride film, 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, in order to improve heat retention, silica (Japanese Patent Publication No. 47-13853) is added to the ethylene-vinyl acetate copolymer resin.
Addition of fillers such as magnesium compounds (JP-A-59-226037), hydrotalcite (JP-A-6O-104141), water-absorbing resin (JP-A-6L-81446)
and ethylene-vinyl alcohol copolymer resin (JP-A-55
-118941).

Further, JP-A-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-58-160146 discloses a film in which a polyolefin layer containing a water drop preventive agent is laminated with a polyolefin layer to which a metal-containing organic compound is added. An agricultural film is disclosed in which a base material layer mainly composed of city polyethylene (hereinafter sometimes abbreviated as L-LDPE) and a resin layer containing a surfactant are laminated. However, it was found that these laminated films did not reach the level of heat retention improvement required in 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 these shortcomings, 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, they 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 with a specific multilayer structure.

[Means and effects for solving the problems] Therefore, the present invention relates to a multilayer film for agricultural use, and the present invention relates to a multilayer film for pickled vegetables containing hydrotalcite or a related compound thereof and an antifogging agent. (A) contains 1 to 40% by weight of hydrotalcite or its analogues, and the content of the antifogging agent is 0.3 or less by weight relative to the hydrotalcite or its analogues; an ethylene-vinyl acetate copolymer resin layer with a resin and/or vinyl acetate content of 20% by weight or less; Vinyl acetate content in a weight ratio of 3 or less to the antifogging agent
It is characterized in that it contains an ethylene-vinyl acetate copolymer layer of 0 to 20% by weight, and that the layers (A) and Φ) are present on the surface of the multilayer film.

In the present invention, the high-pressure polyethylene resin or ethylene-vinyl acetate copolymer resin constituting one of the outer layers is produced by reacting ethylene or ethylene and vinyl acetate by a high-pressure radical polymerization process. High-pressure polyethylene has a density of 0.935 El/cm3 to 0.91
0. A p/shoulder 3 polyethylene is used. Further, as the ethylene-vinyl acetate copolymer resin, an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 20% by weight or less is used. If the vinyl acetate content exceeds 20% by weight, the heat resistance will be poor and it will cause fusion troubles, which is not preferable.

Melt flow rate of high-pressure polyethylene or ethylene-vinyl acetate copolymer resin (hereinafter abbreviated as "for", unit: !i
'/10m1n) is 0.5 to 20, preferably 0.5
~10.

If the edge is too low, the formability of the film, especially the extrusion processability and high-speed stretchability, will deteriorate, which is not preferable.

If the radius becomes large, the mechanical strength decreases, which is not preferable.

(A) What is hydrotalcite or its analogous compound added to the layer (hereinafter abbreviated as hydrotalcite)?
Zx(OH)2(An-)X/n-mHzO, ■・(1
) In the formula, M2+ represents a divalent metal ion selected from the group consisting of mono, Ca and Zn, An- represents an n-valent anion, and X and m satisfy the conditions of the following formula, 0 < These include compounds and fired products thereof that satisfy x < 0.5 0≦m≦2.

Examples of n-valent anions represented by At1- in the above formula (1) include ct'''', Br-, I'''', No3''
;, czo4-+so4*co3. sto, , HP
Examples include anions such as O4, HBO3, PO4, etc.

A specific example of this is Kyowa Chemical Industry (Old Alkamizer).
1 (X=0.33, m=0.5, A=CO3)
, Alcamizer 2 (x=0.331m=0.A=Co
3'-) and the like.

The average particle size is preferably 10μ or less, more preferably 3μ
The following are preferably used. Average particle size is 10μ
If it exceeds this value, the strength and transparency of the film will be 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 from high-pressure ethylene or ethylene-vinyl acetate copolymer resin/hydrotalcite=99-60/1-40 parts by weight.

More preferably, the ratio is 98-75/2-25.

If the amount deviates from the above range and is too small, the so-called infrared absorbing ability will decrease 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-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, preventing the soil temperature inside the greenhouse from rising, 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 susceptible to tearing and the workability of the film being stretched.

It is basically preferable that this layer (A) does not contain an antifogging agent, but 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.
This is undesirable because it ultimately reduces the visible light transmittance of the film, which reduces the transmission of sunlight 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 10 to 20.
It is a copolymer with a weight i%. Such a copolymer is produced by reacting ethylene and vinyl acetate through a high-pressure radical polymerization process, with a polymerization ratio of 0.5 to 10, preferably 0.
5 to 5 are used. If the edge is too small, the film's formability, particularly its extrusion processability and high-speed stretchability will deteriorate, which is not preferable. In addition, if R is too large, the moldability of the film, especially bubbles in inflation molding, becomes unstable, which is not preferable.

The vinyl acetate content of the ethylene-vinyl acetate copolymer resin used is preferably 10 to 20% by weight, and if it is less than 10%, the antifogging properties will deteriorate, which is not preferable. On the other hand, if it exceeds 20 inches, the anti-fogging 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:
Examples include polyoxyalkylene ethers, partial esters of polyhydric alcohols, partial esters of alkylene oxide adducts of polyhydric alcohols, alkali metal salts of higher alcohol sulfates, alkylaryl sulfonates, quaternary ammonium salts, and fatty acid amine derivatives.

Specifically, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene nonylphenyl ether, polyethylene glycol monomer or lumitate, polyethylene glycol monostearate, polyoxyethylene rubitan monolaurate, polyoxyethylene sorbitan. Monopalmitate, Glycerin Monolaurate, Glycerin Monopalmitate, Glycerin Monostearate, Glycerin Monooleate, Pentaerythritol Monolaurate, Sorbitan Monopalmitate, Sorbitan Monobehenate, Sorbitan Distearate, Diglycerin Monooleate, Tri Glycerin diolate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium butylnaphthalenesulfonate, cetyltrimethylammonium chloride, alkyldimethylpendylammonium chloride, dodecylamine hydrochloride, laurylamide ethyl laurate phosphate, triethylcetylammonium iodide , oleylaminodiethylamine hydrochloride, and the basic pyridinium salt of 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, sorbitol, glycerin, polyglycerin, and 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 in the range of 0.1 to 2% by weight based on the ethylene-vinyl acetate copolymer resin. 0,1
If it is less than % by weight, the anti-fogging properties will deteriorate, which is not preferable. Double-
If it exceeds 1 m%, 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 have a thickness of 30μ or more. If this thickness is small, the anti-fogging properties will be poor.

Although no-idrotalcite may be added to this ethylene-vinyl acetate copolymer resin layer, it is desirable that the amount added is 3 or less based on the weight ratio of the antifogging agent. If this value is exceeded, 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 the layers (A) and (2) are laminated.
It is also possible to use it as a multilayer film with three or more layers: a circuit layer provided with an intermediate layer, an intermediate layer, and a (B) layer.

The resin used for the intermediate layer is a variety of polyolefins that are widely used in this field, such as polyethylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-unsaturated caldic acid ester copolymer, and polypropylene. The system resin can be selected and used as appropriate.

Of course, it is also possible to blend and reuse the multilayer film of the present invention.

This layer may also contain hydrotalcite and an antifogging agent, if necessary. 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-
An example of the intermediate layer is an olefin copolymer or/and an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 20% or less, and a layer containing 5% or more of hydrotalcite.

Each layer of the above structure may contain various other additives commonly used in this technical field, if necessary.

Examples of such other additives include antioxidants, light stabilizers, UV absorbers, antistatic agents, lubricants, antiblocking agents, antifogging agents, and various other additives well known in the art. can be mentioned.

The agricultural film of the present invention is not only a transparent film, but also
Films colored with pigments, dyes, etc. are also formed.

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, preferably 0.0, considering strength, performance, production cost, etc.
The thickness ranges from 5 to 0.2 scale. Further, the thickness ratio of each layer can be arbitrarily selected as long as the sum of the thicknesses of the intermediate layer and the (B) layer satisfies 0.03 m++ or more.

Further, 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 (2) layer on the inside.

〔Effect of the invention〕

The present inventors investigated a method for producing an agricultural heat-insulating coating film that is superior to a flexible polyvinyl chloride film using an ethylene polymer.

As a result, we found the following.

(1) For layer (A), high-pressure polyethylene or ethylene-vinyl acetate copolymer resin can be used in consideration of strength, scratch resistance, stretching workability, etc.

(2) Hydrotalcite, an infrared absorbing agent added to the layer (g), has an excellent infrared absorption effect and is one of the best additives for heat-retaining agricultural films. Although it improves as it increases, the appearance,
In terms of transparency, the limit should be 40 inches, preferably 25 inches. 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 to increase the amount of hydrotalcite in layer (A). 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 bleed-out of the antifogging agent, the (B) layer,
The antifogging agent in the intermediate layer moves to the layer (A) due to the concentration gradient,
(B) When added for the purpose of preventing deterioration of the antifogging effect on the layer surface, the weight of the antifogging agent added should be 0.3 or less of the weight of no-hydrotalcite.

As the resin used for the (A) and (B) layers, 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 (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 (B) does not contain hydrotalus f. 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 based on the weight of the antifogging agent.

Based on the above experimental results, the present inventors completed the present invention by specifying the film structure and the type and concentration ratio of the additives added to both the outer layers (A) and (B). .

The agricultural multilayer film of the present invention has excellent heat retention, transparency, antifogging properties, and working strength, and is also superior to polyvinyl chloride film in terms of stain resistance and disposal. Therefore, it is extremely useful as a covering film for greenhouse cultivation.

〔Example〕

Hereinafter, the present invention will be explained in detail based on examples.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

Examples 1-6 Comparative Examples 1-17 As a three-layer inflation molding device, a three-layer die with 150
■φ extruder (manufactured by Tomy Kikai Kogyo@)) was used for the outer layer, a 40 mmφ extruder (manufactured by Modern Machinery Co., Ltd.) was used for the outer layer, a 45 mmφ extruder (manufactured by Zolaco ■) was used for the middle layer, and a 50 mm extruder was used for the inner layer. Molding temperature is 160℃ as a φ extruder (manufactured by Modern Machinery ■)
, a blow ratio of 1.5, a take-up speed of 5 m, and 7 minutes to obtain a multilayer or monolayer film having the structure shown in Table 1. Note that a commercially available soft polyvinyl chloride film was used.

The following evaluation tests were conducted for each film. The results are shown in Table 1.

(1) Anti-fog properties at low temperatures A thermal container (diameter 1
The upper part of the sample (5 cm, height 17 cm) was sealed with a sample, and left to stand in a cold air circulation type cold room at -10°C, after which it was removed for 20 hours, returned to room temperature, and left to stand for 4 hours. This cycle was repeated 7 times.

The film was evaluated on a scale of 10, with 10 being completely transparent and no fogging occurring 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 degrees from the horizontal on a thermostatic water pail maintained at 50°C, and the state of water condensation on the inner surface of the film was observed over time to confirm anti-fogging properties at low temperatures. Similar to gender, it was evaluated on a 10-point scale.

(3) Dust resistance A laminated film was stretched for 4 months in a tunnel created for the measurement of heat retention described below. ). The sunlight transmittance was measured using an illuminance meter (manufactured by Tokyo Photoden, model ANA 300).

A- 3 inches or less, B- 3 to 10 inches, C- 10% or more (A) Heat retention This laminated film was stretched in an airtight manner on an arch-shaped construction to create a tunnel. The arch-shaped construction body had a height of approximately 0.65yy+ and a width of approximately 1.5m.

The difference in temperature inside and outside the house at a height of 20 cm from the ground is 10
The average was calculated every minute for 7 days from 6:00 pm to 6:00 the next morning (January 1986, located in Ichihara City, Chiba Prefecture). The results are shown in Table 1.

(5) Strength at break The strength at break in the MD force direction and TD force direction of the multi-layered film was measured by a tensile test (based on JIS K 6783).

(6) Elongation at Break The elongation at break of the laminated film in the MD force direction and the TD force direction was measured in the same manner as the method for measuring the strength at break.

(7) Falling ball impact strength Measured in accordance with ASTM D1709A method.

(8) Film Stiffness Film stiffness was measured using Handle-0-Meter.

(9) Tensile strength MD of laminated film according to JIS K 6783
The force direction and TD force direction tensile strength were measured.

The results are shown in Table 1.

Claims (2)

[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) 1 to 40% by weight of hydrotalcite or a related compound thereof and an antifogging agent. (B) a high-pressure polyethylene resin having a weight ratio of 0.3 or less to hydrotalcite or its related compounds and/or an ethylene-vinyl acetate copolymer resin layer having a vinyl acetate content of 20% by weight or less; Ethylene containing 10 to 20% by weight of vinyl acetate, which contains 0.1 to 2% by weight of an antifogging agent, and the content of hydrotalcite or its analogous compound is 3 or less based on the weight ratio of the antifogging agent. An agricultural multilayer film comprising: a vinyl acetate copolymer layer; and the layers (A) and (B) are present on the surface of the multilayer film. (2) The agricultural multilayer film according to claim 1, wherein the inner layer is an outer layer (A) and the layer (B) is an inner layer.