Agricultural film

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to an agricultural film having excellent weather resistance, dripping property, heat retention and transparency.

【0002】

[Conventional technology]

Agricultural films used for house and tunnel cultivation are based on branched low-density polyethylene (LDPE), ethylene-vinyl acetate copolymer (EVA), linear low-density polyethylene (LLDPE), etc. The main product is soft plastic with a size of about 30 to 200 μm. The important performance of these resins as an agricultural film is weather resistance, dripping property, heat retention and transparency. In recent years, due to the problem of cost increase in agricultural work and labor shortage, it has been desired to develop a film that can be used for a long period of time until it is necessary to replace the house as much as possible.

【0003】

First, regarding weather resistance, various developments have been made in order to prevent deterioration of the film and to obtain an agricultural film having a longer life and better performance. In the presence of oxygen in the air, the film is deteriorated by ultraviolet rays in sunlight, and the strength and elongation are reduced and the film is damaged. In order to improve this, various weather resistance stabilizers (deterioration inhibitors) have been developed and used by being added to the film.

【0004】

This weather resistance stabilizer can be roughly divided into an ultraviolet absorber and a light stabilizer. In recent years, the light stabilizer is more effective for thin agricultural films, has a large improvement effect, and the amount added is large. It is the mainstream of weather resistance stabilizers because it requires less and the cost is lower. Conventionally, nickel-based compounds have been the main light stabilizers, but in recent years, many hindered amine-based compounds have been developed as light stabilizers, and because of their excellent performance, they can be added in small amounts. It has become the mainstream of weather resistance stabilizers.

【0005】

Next, regarding the drip property, drip is to treat the water droplets adhering to the inner surface of the film of the house as a water film, and by performing this drip treatment, the transmitted sunlight into the house and the tunnel is transmitted. We try to increase the amount as much as possible, raise the internal soil temperature and temperature, promote photosynthesis of plants, promote the growth of crops in a healthy state, and suppress the outbreak of diseases. Conventional methods of drop treatment include a drop agent kneading method in which a drop agent is kneaded into a film-forming resin to form a film, and a commonly used drop agent is, for example, Nonionic, anionic, and cationic surfactants.

【0006】

Regarding heat retention, the temperature in the house at night, during, and in the dawn decreases as the outside temperature drops, so the temperature difference of 1 to 2 ° C during this time is the integrated temperature (daily average). Considering temperature x number of days (2500 to 3000 ° C in the case of paddy rice), it has a great influence on the final yield and harvest time of agricultural products, so it is one of the important performances of agricultural films. Fillers such as silica powder (Tokuko Sho 47-13853), magnesium compounds (Tokuhei 3-50791), and hydrotalcite (Tokuko Sho 62-31744) are used as heat retaining agents for agricultural films. There are methods such as addition of water-absorbent resin (Japanese Patent Laid-Open No. 61-81446) and ethylene / vinyl alcohol copolymer (Japanese Patent Laid-Open No. 55-118941). In particular, hydrotalcite is a substance with a good balance of heat retention and transparency because it has performance as a heat retention imparting agent and the deterioration of film transparency caused by the addition of an inorganic filler is less likely to occur than others. It is known that there is.

【0007】

Needless to say, transparency is indispensable for crops that grow under sunlight, and agricultural films are preferably as transparent as possible.

【0008】

[Problems to be Solved by the Invention]

However, a hindered amine-based light stabilizer for imparting weather resistance generally has a small molecular weight and easily escapes from the film, so that its effect as a weather resistance stabilizer cannot be maintained for a long period of time. In addition, hindered amine-based light stabilizers with excellent light-stabilizing effects are alkaline, and these are pesticides sprayed for the purpose of pest control of crops in greenhouses, such as organochlorine pesticides and organophosphorus pesticides. There is a problem that the effect as a weather resistance stabilizer is reduced due to a chemical reaction with an acidic substance generated when the greenhouse is decomposed.

【0009】

As a solution to this problem, it has been proposed in Japanese Patent Application Laid-Open No. 63-175072 that it is effective to use hydrotalcite as a neutralizing agent in combination with a hindered amine-based light stabilizer. Due to the low molecular weight of the agent, escape from the film is unavoidable and has not led to an essential solution. For these reasons, among the polyolefin-based agricultural films currently in use, those that satisfy all of the above four performances required for agricultural films have not yet been obtained.

【0010】

The present invention provides an agricultural film having four excellent performances of heat retention, transparency, weather resistance, and drip resistance.

【0011】

[Means for solving problems]

As a result of diligent studies to improve these problems and obtain a performance-balanced agricultural film with good heat retention and transparency, as well as excellent dripping and weather resistance, we decided to use a thermoplastic resin. A conventional light stabilizer was added by containing an ethylene-based copolymer having hindered amine in the side chain and hydrotalcites, and applying a drip agent to the inner surface of the film or blending it in the film. The present invention has been completed by finding that an agricultural film having an excellent weather resistance life, excellent dripping property, good heat retention and transparency, and an excellent performance balance can be obtained as compared with an agricultural film.

【0012】

[Structure of the Invention]

In the first aspect of the present invention, an ethylene-based copolymer having a hindered amine obtained by copolymerizing ethylene and a cyclic aminovinyl compound in a side chain is mixed in a thermoplastic resin film at a ratio of 0.05 to 5 in units of the vinyl compound. It is a thermoplastic resin film containing 0.5 to 20% by weight of hydrotalcites, and is characterized in that a drip agent is applied to the surface of the film or blended in the film. It provides an agricultural film having a drip property.

【0013】

The second aspect of the present invention is to use an ethylene-based copolymer having a hindered amine in the side chain obtained by copolymerizing ethylene and a cyclic aminovinyl compound in a proportion of the vinyl compound unit in the thermoplastic resin film of 0.05 to 5 Agricultural use consisting of two or more layers of a laminate having a thermoplastic resin film layer (A) containing 0.5 to 20% by weight of hydrotalcites and an inner layer (B) of a resin film having drip property. It provides a film.

【0014】

[Specific Description of the Invention]

(Resin for film) As the thermoplastic resin used in the present invention, polyolefins such as LDPE, EVA, LLDPE, etc. are suitable, and these are generally used in large quantities as agricultural films.

【0015】

(Ethylene-based copolymer having hindered amine in the side chain) The ethylene-based copolymer having hindered amine in the side chain used in the present invention includes ethylene (A) and a cyclic amine vinyl compound represented by the following general formula (I). B) [0016]

[Chemical 2]

【0017】

(In the formula, R₁And R₂Is a hydrogen atom or a methyl group, R₃Is a copolymer with a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, respectively), and the ratio of (B) to the sum of (A) and (B) is less than 1 mol%, preferably 0.1. An ethylene-based copolymer characterized in that the MFR of the copolymer is 0.1 to 200 g / 10 minutes at ~ 0.7 mol% is used.

【0018】

Above all, it is preferable that the ratio of (B) isolated in the copolymer is 83% or more with respect to the total amount of (B). A typical example of the vinyl compound of the above general formula (I) is as follows. 4-Acryloyloxy-2,2,6,6-tetramethylpiperidin 4-Acryloyloxy-1,2,2,6,6-pentamethylpiperidin 4-Acryloyloxy-1-ethyl-2,2,6,6-tetramethylpiperidine 4-Acryloyloxy-1-propyl-2,2,6,6-tetramethylpiperidin 4-Acryloyloxy-1-butyl-2,2,6,6-tetramethylpiperidine 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine 4-methacryloyloxy-1,2,2,6,6-pentamethylpiperidin 4-Methylloyloxy-1-ethyl-2,2,6,6-tetramethylpiperidin 4-methacryloyloxy-1-butyl-2,2,6,6-tetramethylpiperidin 4-Crytonoyloxy-2,2,6,6-tetramethylpiperidin 4-Crytonoyloxy-1-propyl-2,2,6,6-tetramethylpiperidin The ethylene-based copolymer having this hindered amine in the side chain is produced by the high-pressure radical copolymerization method described in detail in Japanese Patent Application No. 2-192970.

【0019】

The proportion of the structural unit based on the cyclic amine vinyl compound in the thermoplastic resin film is 0.05 to 5% by weight, preferably 0.1 to 4% by weight. If it is less than 0.05% by weight, the effect of improving the weather resistance is small, and if it exceeds 5% by weight, no further improvement in weather resistance can be expected, which is economically disadvantageous. The ethylene-based copolymer having hindered amine in the side chain may be uniformly contained in the single-layer film, or may be concentrated and contained in the outermost layer of the multilayer film (the side where the agricultural film is exposed to wind, rain and sunlight). You may let me. Up to a certain concentration, the larger the content, the greater the effect of improving the weather resistance. Therefore, it is preferable to concentrate the content in the outermost layer as a multilayer structure from the viewpoint of the weather resistance effect and economy.

【0020】

(Hydrotalcites) The hydrotalcites used in the present invention (hereinafter, simply abbreviated as hydrotalcites) are the general formula (II). [0021] [0021]

[Chemical 3]

【0022】

(However, in the ceremony, M²⁺Indicates a divalent metal ion selected from the group consisting of Mg, Ca and Zn, and x and m satisfy the conditions of the following formula. 0 <x <0.5 0 m 2) It is a compound represented by, or a fired product thereof.

【0023】

In the above formula, A^n-An example of an n-valent anion represented by is Cl^-, Br^-, I^-, NO₃^2-, ClO₄^-, SO₄^2-, CO₃^2-, SiO₃^2-, HPO₄^2-, HBO₃^2-, PO₄^2-Anions such as, etc. can be exemplified. Specific examples thereof include DHT-4A, DHT-4SA, Alchemizer 1, Alchemizer 2 and the like of Kyowa Chemical Industry Co., Ltd.

【0024】

The amount of hydrotalcite added is 0.5 to 20% by weight, preferably 1 to 10% by weight in the film. The average particle size of hydrotalcite is 5 μm or less, preferably 0.05 to 2 μm. If the amount deviates from the above range and is too small, the effect of improving weather resistance is weak. Further, if a large amount is added or the average particle size is excessive, the strength of the film may be lowered or the transparency may be impaired.

【0025】

(Drop agent) The drip agent used in the present invention is added in an amount of 0.1 to 5% by weight in a thermoplastic resin film, or is applied to the surface of the film. When added to a film, if it is less than 0.1% by weight, the effect as a drip agent is weak. On the other hand, if it exceeds 5% by weight, the film surface becomes sticky, dust and the like adhere to it, and the transparency is impaired.

【0026】

As the drip agent added to the film, a commonly used drip agent can be used. For example, nonionic, anionic and cationic surfactants are used. Specifically, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene nonylphenyl ether, polyethylene glycol monopalmitate, polyethylene glycol monostearate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmi. Tate, glycerin monolaurate, glycerin monopalmitate, glycerin monostearate, glycerin monoolate, pentaerythritol monolaurate, sorbitan monopalmitate, sorbitan monobehenate, sorbitan distearate, diglycerin monoolate, triglyceringio Rate, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium butylnaphthalene sulfonate, cetyltrimethylammonium chloride, alkyldimethylbenzylammonium chloride, dodecylamine hydrochloride, laurylamide ethyl phosphate laurate, triethylcetylammonium iodide, oleyl Examples thereof include aminodiethylamine hydrochloride and basic pyridinium salt of dodecylpyridinium sulfate.

【0027】

Of these, particularly preferable are nonionic surfactants containing 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 as main components. Examples include system surfactants. The drip agent used for application is mainly composed of an inorganic hydrophilic colloidal substance and a hydrophilic organic compound. For example, Tokusho 63-45432, Tokukou 63-45717, It is a compound shown in Japanese Patent Publication No. 64-2158.

【0028】

Examples of inorganic hydrophilic colloidal materials include colloidal silica, colloidal alumina, and colloidal Fe (OH).₂, Colloidal Sn (OH)₄, Colloidal TiO₂, Colloidal BaSO₄And colloidal lithium silicate and the like. Particularly preferred substances are colloidal silica and colloidal alumina.

【0029】

Examples of hydrophilic organic compounds include copolymers containing 0.1 to 40% by weight of various surfactants (nonionic, anionic, cationic) and hydroxyl group-containing vinyl monomer components, or parts thereof or completely neutralized. Examples thereof include compounds and sulfonic acid group-containing polyester resins. 2-Hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxyethyl methacrylate can be used as the hydroxyl group-containing vinyl monomer, and acrylic acid alkyl ester and methacrylic acid alkyl ester can be used as the vinyl monomer copolymerizable therewith. Styrene, acrylonitrile, acrylic acid and the like can be used.

【0030】

The amount of drip agent applied to the inner layer of the film is 0.05 to 5 g / m.², Preferably 0.1 ~ 2g / m²Is. Application amount is 0.05g / m²Below, the drip-sustaining effect is low, 5 g / m²If it exceeds, the transparency of the film is impaired, which is not preferable. The method of applying the drip agent may be any of various roll printing methods, dipping methods and spraying methods. Further, the coating can be carried out by an in-line coating that is subsequently performed after film molding, an outline coating that is performed by a rewinding step after film molding / winding, or a method of spraying and coating on the inner surface of the film after it has been stretched.

【0031】

As a method of adding the drip agent, a method of applying the drip agent to the surface of the film is preferable to a so-called kneading method of adding the drip agent into the film because the effect of the drip is maintained. The thickness of the entire layer of the agricultural film is 0.03 to 0.3 mm, preferably 0.05 to 0.2 mm. If it is too thin, the strength of the film will be insufficient, which is not preferable. Moreover, if it is too thick, the cost will increase, which is not preferable.

【0032】

The film of the present invention can be used as a single layer or multiple layers. When used as a multilayer, both layers are a thermoplastic resin layer (A) containing an ethylene-based copolymer having a hindered amine in the side chain and a hydrotalcite compound, and a resin inner surface layer (B) having drip-like property. It may be used as a two-layer film in which the above layers are laminated, or it may be used as a multilayer film having three or more layers (A) / intermediate layer / (B) layer provided with an intermediate layer. At that time, it is desirable that the layer (A) is the outer layer or the intermediate layer of the film, and the layer (B) is the inner layer of the film.

【0033】

In the case of a laminated structure, in the case of a two-layer film (A / B), the wall thickness of (A) is 5 to 250 μm, and the wall thickness of (B) is 5 to 250 μm. In the case of a three-layer film, the wall thickness of the (A) layer is 5 to 200 μm, the wall thickness of the intermediate layer is 5 to 200 μm, and the wall thickness of the (B) layer is 5 to 50 μm. Further, the film of the present invention can be added with wax, antioxidant, antistatic agent, ultraviolet absorber, lubricant, inorganic filler and the like, if necessary.

【0034】

[Example]

Here, the present invention will be described in detail with reference to Examples and Comparative Examples. The methods for measuring weather resistance, drip resistance, heat retention, and transparency in Examples and Comparative Examples are shown below.

【0035】

<Weather resistance> The test film was attached to a mini-house with a height of 60 cm and a length of 1.5 m, and the weather resistance was examined. The evaluation method is to punch the film laterally with a punching blade shape to prepare a test piece, measure the breaking point elongation with a shopper type tensile tester, and weather resistance when the breaking point elongation is 100%. It was the end point of deterioration.【0036】

<Dripping property> A test film was attached to a mini-house with a height of 60 cm and a length of 1.5 m, and the dripping property was examined. In the evaluation method, changes in the state of water droplet adhesion on the inner surface of the film were observed, and in the measurement of the drip property, the end point of the drip property was when water droplets adhered to about 50% of the inner surface of the film.

【0037】

<Heat retention> A test film was attached to a mini-house with a height of 60 cm and a length of 1.5 m, and the temperature inside and outside the house was measured at 4:00 am, and the temperature difference was examined. This was done for 10 days and the average value was calculated.

【0038】

<Transparency> The total light transmittance of the film was measured. The method complies with JIS K 6714.

【0039】

<Example 1> The inner and outer layers (A) and (B) are ethylene-vinyl acetate copolymers having a vinyl acetate content of 3% by weight, and the intermediate layer (C) has an ethylene-vinyl acetate copolymer having a vinyl acetate content of 15% by weight. Ethylene-based copolymer and hydrotalcite (Kyowa Kagaku Kogyo Co., Ltd., DHT-4A (trade name), average particle size, which uses the coalescence as the base resin and has hindered amine in the side chain synthesized by the method shown below. 0.4 μm) was blended as shown in Table 1, and a three-layered film with a thickness of 100 μm (A15 μm, C70 μm, B15 μm) and a width of 1800 mm was obtained by the inflation method. A brush roll coater with a roll width of 2000 mm is used to coat the film at a coating speed of 8 m / min.

【0040】

This was evaluated for weather resistance life, dripping life, heat retention, and transparency by the above method. Evaluation of weather-resistant life and drip-resistant life began on October 30, 1985. The evaluation results are shown in Table 1.

【0041】

<Production method of ethylene-based copolymer having hindered amine in the side chain> 4-Acryloyloxy-2,2,6,6-tetramethylpiperidine dissolved in ethylene and ethyl acetate using a stirring autoclave type continuous reactor. And as a catalyst, tertiary-butyl peroxypivalate dissolved in normal hexane was continuously supplied, and the polymerization pressure was 2000 kg / cm.²It was copolymerized at a polymerization temperature of 200 ° C.

【0042】

The MFR of the obtained copolymer is 2.7 g / 10 minutes, the content of 4-acryloyloxy-2,2,6,6-tetramethylpiperidine unit is 3.0% by weight, and it exists in isolation. The ratio is¹³It was 85% as measured by C NMR.

【0043】

<Manufacturing method of drip agent (coating type)> A drip agent having an active ingredient concentration of 2% by weight obtained by adding water to the following active ingredients (a) to (c) and stirring and mixing them. (a) Colloidal silica: 70% by weight (Catalyst Chemicals, Inc., Cataloid S1-350) (b) Silane derivative: 5% by weight (γ-ureidopropyltriethoxysilane) (c) Nonionic surfactant: 25% by weight (polyoxyethylene (7 mol) oleic acid ester) [0044]

<Example 2> The basic formulation was the same as in Example 1, and only the amount of the ethylene-based copolymer having hindered amine in the side chain was increased and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

【0045】

[table 1]

【0046】

<Example 3> The basic formulation was the same as in Example 1, and only the amount of the ethylene-based copolymer having hindered amine in the side chain was increased and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

【0047】

<Example 4> The basic formulation was the same as in Example 1, only the amount of hydrotalcite compounded was increased, and the evaluation was carried out in the same manner as in Example 1. The evaluation results are shown in Table 2.

【0048】

[Table 2]

【0049】

<Example 5> The basic formulation was the same as in Example 1, only the amount of hydrotalcite compounded was increased, and the evaluation was carried out in the same manner as in Example 1. The results of the evaluation are shown in Table 3.

【0050】

<Example 6> The basic formulation was the same as in Example 1, the drip agent was changed to a kneading type (polyoxyethylene lauryl ether), and the evaluation was carried out in the same manner as in Example 1. The evaluation results are shown in Table 3.

【0051】

[Table 3]

【0052】

<Example 7> An ethylene-vinyl acetate copolymer having a vinyl acetate content of 13% by weight was used as the base resin, and a single-layer film having a thickness of 100 μm and a width of 1800 mm was prepared by a normal inflation method. Others were the same as in Example 1 and evaluated in the same manner. The evaluation results are shown in Table 4.

【0053】

<Example 8> An ethylene-vinyl acetate copolymer having a vinyl acetate content of 13% by weight is used as the base resin, a drip agent is kneaded into the base resin (polyoxyethylene lauryl ether), and the thickness is increased by the inflation method. A single-layer film having a width of 100 μm and a width of 1800 mm was used. Others were the same as in Example 1 and evaluated in the same manner. The evaluation results are shown in Table 4.

【0054】

[Table 4]

【0055】

<Comparative Example 1> The basic formulation was the same as in Example 1, and only the amount of the ethylene-based copolymer having hindered amine in the side chain was increased and evaluated in the same manner as in Example 1. The results of the evaluation are shown in Table 5.

【0056】

<Comparative Example 2> The basic formulation was the same as in Example 1, only the amount of hydrotalcite compounded was increased, and the evaluation was carried out in the same manner as in Example 1. The results of the evaluation are shown in Table 5.

【0057】

[Table 5]

【0058】

<Comparative Example 3> The basic formulation was the same as in Example 1, and the drip agent was evaluated in the same manner as in Example 1 except for the coating type and the kneading type. The results of the evaluation are shown in Table 6. <Comparative Example 4> The basic composition was the same as in Example 1, and a hindered amine type light stabilizer manufactured by Company S was used instead of the ethylene-based copolymer having hindered amine in the side chain, and the evaluation was carried out in the same manner as in Example 1. The results of the evaluation are shown in Table 6.

【0059】

[Table 6]

【0060】

<Comparative Example 5> Instead of the ethylene-based copolymer having hindered amine in the side chain, the hindered amine type light stabilizer bis (2,2,6,6-tetramethyl-4-piperidyl) sevacate manufactured by S company was used. An ethylene-vinyl acetate copolymer having a vinyl acetate content of 13% is used as the base resin, and a single-layer film having a thickness of 100 μm and a width of 1800 mm is obtained by a normal inflation method. Others were the same as in Example 1 and evaluated in the same manner. The results of the evaluation are shown in Table 7.

【0061】

<Comparative Example 6> The basic composition was the same as in Example 1, and the hydrotalcite was changed to one having a large average particle size (average particle size = 5.6 μm). The evaluation was performed in the same manner as in Example 1, and the evaluation results are shown in Table 7.

【0062】

[Table 7]

【0063】

<Comparative Example 7> Examples include an ethylene-based copolymer having a hindered amine in the side chain and an ethylene-based copolymer having a hindered amine in the side chain in which the proportion of vinyl compounds isolated is 76%. It was the same as 1 and evaluated in the same way. The results of the evaluation are shown in Table 8.

【0064】

<Comparative Example 8> As a comparison target of heat retention and transparency, only an ethylene-vinyl acetate copolymer having a vinyl acetate content of 13% was used as a film, and the evaluation results of heat retention and transparency are shown in Table 8. Shown in.

【0065】

[Table 8]

【0066】

[Effect of the invention]

As shown in the examples, in the present invention, the thermoplastic resin contains an ethylene-based copolymer having a hindered amine in the side chain and a hydrotalcite compound, and a drip agent is applied to the inner surface of the film. Alternatively, by blending it in a film, it is possible to obtain an agricultural film having a better balance of performance with better weather resistance life, drip property, heat retention and transparency than the conventional agricultural film to which a light stabilizer is added. It is a thing.