JPH09302119A - Production of agricultural film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an agricultural film of an anti- fogging agent precoating type excellent in initial anti-fogging properties, anti- fogging durability and transparency, by using a solution of an anti-fogging agent composition excellent in economic efficiency and handleability and long in pot life without requiring the use of an organic solvent. SOLUTION: In forming anti-fogging agent layer by applying a solution of an anti-fogging agent composition to at least one side of a thermoplastic synthetic resin film and drying, a composition comprising an inorganic colloidal sol obtained by blending colloidal alumina and colloidal silica charged differently in electric charge mutually in the ratio of the solid content of (80-20):(20-80) (the total of 100) by weight, a nonionic surfactant and water, prepared by mechanical shear stirring and having 1-1,000mPa.s viscosity at a room temperature is used as the anti-fogging agent composition to form an anti-fogging agent layer having 0. 05-1g/m<2> application amount of the anti-fogging agent calculated as that after drying.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a thermoplastic synthetic resin using an antifogging agent composition liquid which does not require the use of an organic solvent, is excellent in economical efficiency and handleability, and has a long pot life. The present invention relates to a method for producing an agricultural film, which comprises forming an antifogging agent layer on at least one surface of the film to produce an agricultural thermoplastic synthetic resin film excellent in initial antifogging property, antifogging durability and transparency.

[0002]

2. Description of the Related Art Agricultural thermoplastic synthetic resin film (hereinafter referred to simply as "film") used in greenhouses, pipe houses, etc.
However, depending on the temperature and humidity of the atmosphere, cloudiness may occur on the film surface, which impairs the transmission of sunlight and slows plant growth, or water droplets fall onto cultivated plants, causing There are inconveniences such as damage to buds, stems, leaves, etc., causing diseases, and making workers in greenhouses and pipe houses uncomfortable.

In order to improve such a point, for the purpose of imparting antifogging property to the film, an antifogging agent such as a surfactant is kneaded into the base resin itself, and the obtained resin composition is formed into a film. I was getting a film. However, in such a kneading-type film, the limit of the antifogging sustainability is generally 1.5 years, and thereafter, in order to recover the antifogging property, the film extended in the pipe house is treated with the antifogging agent composition liquid. It was necessary to perform spray coating with a power sprayer or the like.

However, this spray coating method requires a large amount of antifogging agent composition liquid, which leads to an increase in cost, and also causes uneven spraying on the film, impairing the antifogging property of the pipe house. However, there is a problem that the time when the application work is possible is limited to the time when the crop in the pipe house is not cultivated.

[0005]

In order to solve the above-mentioned problems, a method has been proposed in which a film is preliminarily coated with an antifogging agent composition liquid (Japanese Patent Publication No. 1-33492 and Japanese Patent Laid-Open Publication No. Hei. 3-50288 gazette). The antifogging agent composition liquid used for this pre-coating is required to have stability and easy coating properties, and the antifogging agent layer formed on the film has an initial antifogging property and an antifogging property. Cloudiness persistence,
Those having characteristics such as coating uniformity are required.
It is important that the cost of the entire process is low.

However, in the antifogging agent composition liquid of Japanese Patent Publication No. 1-33492, it is necessary to use an alcoholic organic solvent to dissolve the acrylic polymer, and as an antifogging agent, a negative charge is applied. Since the colloidal silica described above cannot be used, the selection range of the constituent material is narrowed and it is economically disadvantageous.

Further, in the case of the method of JP-A-3-50288, the concentration of the nonionic surfactant in the antifogging agent composition liquid is limited to 0.05 to 15%. When the concentration of a general nonionic surfactant in the composition is 10% or more, the viscosity of the antifogging agent composition at room temperature is 1000 m.
Pa · s, which causes uneven coating during coating,
There was a problem with the transparency of the film.

In view of the above points, an object of the present invention is that it is not necessary to use an organic solvent, is excellent in economical efficiency and handleability,
Moreover, by using an antifogging agent composition liquid having a long pot life, there is provided a method for producing an antifogging agent pre-coated agricultural film excellent in initial antifogging property, antifogging durability and transparency. Especially.

[0009]

The method for producing an agricultural film according to the present invention comprises applying an antifogging agent composition liquid to at least one side of a film and drying the composition to form an antifogging agent layer. As the composition liquid, colloidal alumina and colloidal silica, which are charged with different charges, are contained in a solid content weight ratio of 80 to 20:20 to 80 (total 100
Of the inorganic colloid sol, a nonionic surfactant, and water, which are prepared by mechanical shearing stirring and have a viscosity at room temperature of 1 to 100.
It is characterized in that the composition liquid having 0 mPa · s is used to form an antifogging agent layer having a dry coating amount of the antifogging agent of 0.05 to 1 g / m ² .

According to the method of the present invention, for example, an agricultural film having a haze increase rate of 5% or less and a total light transmittance decrease rate of 3% or less before and after the formation of the antifogging agent layer can be produced. it can.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The colloidal alumina and colloidal silica used in the method of the present invention remain on the surface of a film after being applied to the film, and the function of improving the initial antifogging property and antifogging sustainability of the obtained agricultural film. Fulfill.

The average particle size of colloidal alumina and colloidal silica is preferably within the range of 0.1 μm or less. When the average particle size exceeds 0.1 μm,
When the antifogging agent composition liquid containing them is applied to the film surface, the transparency may be lowered.

The average particle size ratio (colloidal alumina and colloidal silica) is preferably 1 to 2. When this ratio exceeds 2, it becomes difficult to cause thickening gelation in a short time when the both are mixed, and the antifogging agent composition liquid is washed off with water after coating, so that the antifogging agent layer is formed. It becomes difficult to form.

The proportion of colloidal alumina or colloidal silica in the inorganic colloid (colloidal alumina, colloidal silica) is 80 to 2 in terms of solid content weight ratio, respectively.
The range is 0 (total 100). This ratio is 8
When it is 0 or more and 20 or less, the surface of the antifogging agent layer formed on the film is easily charged with positive charge or negative charge, and fine particles such as dust charged with positive charge or negative charge are antifogging. It is adsorbed on the surface of the agent layer and the film is easily soiled.

In order to prepare the antifogging agent composition liquid used in the present invention, the colloidal silica colloidal liquid is preferably acidic. A particularly suitable pH is 2-4. When an alkaline colloidal solution is used, this makes the colloidal state unstable with the colloidal alumina acidic colloidal solution, and it is not possible to form a uniform anti-fog agent layer, and the pot life after application of the colloidal solution is shortened. The coating workability may decrease.

The solid content concentration of colloidal alumina and colloidal silica in the antifogging agent composition liquid is preferably 0.1 to 5% by weight, more preferably 0.5 to 3.5, respectively.
% By weight. If the concentration of each of these is less than 0.1% by weight, the film formation due to gelation becomes incomplete, and if it exceeds 5% by weight, the gelation proceeds too rapidly and the pot life becomes short, The coating workability may deteriorate and the coating may become non-uniform due to gelation.

The nonionic surfactant is used to improve the dispersion stability of the antifogging agent composition liquid, improve the wettability and adhesion of the antifogging agent composition liquid to the film, form a uniform gel, and further add water. Contributes to the runoff prevention effect of the gelled film.

Specific examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan alkyl esters, and fatty acid alkylol amides. And cellulose ethers. Of these, cellulose ethers, particularly water-soluble cellulose ethers such as water-soluble methyl cellulose, are preferable from the viewpoints of easy handling that can be used in an aqueous solution and economical efficiency.

The concentration of the nonionic surfactant in the antifogging agent composition liquid is preferably 0.05 to 3% by weight, more preferably 0.4 to 2% by weight. If this concentration is less than 0.05% by weight, a sufficient wetting effect may not be obtained,
On the other hand, if it exceeds 3% by weight, the concentration of the aqueous dispersion becomes high, the workability is deteriorated, and furthermore, the coated surface tends to be non-uniform.

The viscosity of the antifogging composition is 1 at room temperature.
To 1000 mPa · s, especially 2 to 100 m
The range of Pa · s is preferable.

The viscosity of the antifogging agent composition liquid is 1000 mPs.
If it exceeds s, the viscosity is too high, resulting in uneven coating, resulting in a significant decrease in the total light transmittance and a marked increase in haze.

The antifogging composition according to the present invention is usually prepared immediately before coating. For example, in water, an aqueous dispersion concentrate of colloidal alumina, an aqueous dispersion concentrate of colloidal silica,
A water-dispersed concentrated liquid of a nonionic surfactant is sequentially added and mixed, and by thoroughly stirring each mixing, an antifogging agent composition liquid having a long pot life is prepared.

When the above concentrated liquids are mixed with each other, thickening gelation proceeds too quickly, which makes it difficult to apply the antifogging agent composition liquid. Further, in the above sequential stirring, if the stirring is insufficient, the colloidal silica and the colloidal alumina may be gelated as secondary particles or tertiary particles and easily settle, and the pot life may be shortened.

Further, as a stirring method, the rotation speed is 50 so that water, colloidal alumina, colloidal silica and a nonionic surfactant are sufficiently stirred during successive mixing.
It is desirable to drive a medium shearing internal stirrer such as a homogenizer or a colloid mill at 0 rpm or more for 20 seconds or more.

If the number of revolutions is less than 500 rpm, or if the stirring time is less than 20 seconds, stirring tends to be insufficient, and the colloidal silica and colloidal alumina gelate as secondary particles or tertiary particles as they are, and settle. I hate it because the pot life becomes short.

The thermoplastic synthetic resin used as the material resin of the film in the present invention is low density polyethylene (LDPE), ethylene-vinyl acetate copolymer (EV).
A), polyolefins such as linear low-density polyethylene (L-LDPE), and polyvinyl chloride (PVC).

The thermoplastic synthetic resin used in the present invention includes stabilizers, antioxidants, plasticizers, stabilizing aids, heat retaining agents, ultraviolet absorbers, and fog-proofing agents to the extent that the effects of the present invention are not impaired. You may mix additives, such as an agent, a lubricant, and a pigment.

As the heat retaining agent, for example, silicon oxide, silicates, phosphates, glass fine powder and the like are used as the thermoplastic synthetic resin 1.
It is preferably 1 to 20 parts by weight, more preferably 3 to 10 parts by weight, based on 00 parts by weight. If the content of the heat retaining agent exceeds 20 parts by weight, the visible light transmittance may be significantly reduced and the strength of the film may be reduced, and if it is less than 1 part by weight, the heat retaining effect may be lost. There is.

Examples of the ultraviolet absorber include benzophenone type, benzotriazole type, hydroquinone type,
UV absorbers such as salicylic acid type, benzoate type, and cyanoacrylate type are preferably used.

If the thickness of the film used in the present invention is too thin, the mechanical strength tends to be inadequate, and conversely if it is too thick, the film forming process and the subsequent cutting, joining, spreading work of the film, etc. Since it causes inconvenience in handling, the range of 0.02 to 0.3 mm is preferable, and in particular, 0.
The range of 03 to 0.2 mm is preferable.

The film used in the present invention is produced by a conventionally known film forming method, for example, an extrusion molding method such as an inflation molding method, a T-die molding method, a calender molding method, a solution casting method using an extruder. can do.

When the adhesion between the film and the antifogging agent coating layer is not sufficient, the surface of the film is washed with alcohol or water in advance, plasma discharge treatment or corona discharge treatment is performed, and an undercoat paint or primer is used. Pretreatment such as painting may be performed.

The antifogging composition according to the present invention is spray-coated, roll-coated, dip-coated, bar-coated, knife-coated or brush-coated on at least one surface of the film whose surface is pretreated as described above. It is applied by a known method such as a method.

The amount of the antifogging agent composition liquid applied to the film is preferably in the range of 0.02 to 1 g / m ^{2 in} terms of dry time. If the coating amount is less than 0.02 g / m ² , the antifogging sustainability may decrease, and a large amount of energy may be required during drying. Conversely, if it exceeds 1 g / m ² , the antifogging composition The liquid tends to have a high viscosity of 1000 mPa · s or more, and coating unevenness tends to occur.

As a drying method after coating, either natural drying or forced drying may be adopted. In the case of forced drying, the drying temperature is preferably in the range of 50 to 150 ° C. If the drying temperature is less than 50 ° C, the drying cost may be slow and a long drying furnace may be required, which may be disadvantageous in terms of equipment cost. Tube blocking is likely to occur.

For forced drying, a hot air drying method, an infrared ray drying method, a far infrared ray drying method or the like may be appropriately adopted, and the hot air drying method is advantageous in view of drying speed and safety.

A particularly preferred agricultural film obtained by the method of the present invention has a haze increase rate of 5% or less and a total light transmittance decrease rate of 3% or less.

[0038]

The average particle diameters of colloidal alumina and colloidal silica are similar to each other, and they have a positive charge or a negative charge, respectively. Then, by stirring and mixing colloidal alumina and colloidal silica charged with different charges with a medium shearing internal stirrer, an antifogging agent composition liquid having a uniform and long pot life can be obtained. This liquid is applied to at least one surface of a surface-treated film and dried to form an antifogging agent layer.

Since the antifogging agent layer thus formed contains a hydroxyl group, it has a good initial antifogging property and good antifogging durability.

Further, the nonionic surfactant improves dispersion stability of the antifogging composition, improves wettability and adhesion of the antifogging composition to the film, forms a uniform gel, and further , Contributes to the runoff prevention action of the gelled film due to water.

[0041]

EXAMPLES Next, some examples of the present invention and comparative examples for comparison therewith will be shown.

Example 1 Preparation of Aqueous Solution of Nonionic Surfactant Water in a container was homogenized (rotation speed: 1000 r
Methyl cellulose (trade name: Metroze SM-15, manufactured by Shin-Etsu Chemical Co., Ltd.) was added while stirring at pm) to prepare a dispersion liquid having a solid content of 8% by weight.

Preparation of anti-fog composition liquid Colloidal alumina (manufactured by Nissan Kagaku Co., Ltd., trade name: alumina sol 520, average particle size 0.01 to 0.0) was added to 1000 g of water.
167 g of 2 μm, solid content 20% by weight, positive charge was added, and this solution was homogenized (rotation speed: 1000 rp).
m) was stirred for 30 seconds.

167 g of colloidal silica (manufactured by Nissan Kagaku Co., Ltd., trade name: Snowtex O, solid content 20% by weight, average particle diameter 0.01 to 0.02 μm, pH 2 to 4, negative charge) in the obtained liquid. Was added, and the mixture was stirred for 30 seconds with a homogenizer (rotation speed: 1000 rpm).

Further, 167 g of the above aqueous solution of nonionic surfactant was added to the obtained liquid, and the mixture was stirred with a homogenizer (rotation speed: 1000 rpm) for 30 seconds to give an antifog composition having an antifog concentration of 5.3% by weight. A liquid was prepared.

Evaluation of Pot Life of Antifog Composition Liquid The obtained antifog composition liquid was allowed to stand at room temperature for 1 week, and the appearance and the presence or absence of aggregates were visually observed and evaluated according to the following criteria.

◯: No agglomerates were observed even after standing for 1 week Δ: A slight amount of solid content was separated after standing for 1 week x: Aggregates were generated immediately after standing.

The evaluation results are shown in Table 1.

Viscosity Measurement of Antifog Composition Liquid The viscosity of the obtained antifog composition liquid was measured at room temperature (20 ° C.) with a B type viscometer (manufactured by Tokyo Keiki Co., Ltd.).

The measurement results are shown in Table 1.

Manufacture of an original film As the original film, a film having a three-layer structure was used.
The layer thickness ratio was outer layer / middle layer / inner layer = 1/4/1.

As the resin for the outer and inner layers of the film, L-LDPE (linear low density polyethylene) (manufactured by Mitsui Petrochemical Co., Ltd., trade name: ULTZEX2020, MI =
2.1, specific gravity: 0.92), and as the resin for the film middle layer, EVA (ethylene-vinyl acetate copolymer) (Mitsui DuPont Polychemical Co., Ltd., trade name: EV
AFLEX P-1403, vinyl acetate content = 14%,
Using MI = 1.4, specific gravity: 0.93), these resins were formed into a three-layer structure as described above by coextrusion using an inflation molding machine to form a laminated film having a total thickness of 150 μm.

Coating and drying of the antifogging agent composition liquid The surface of the raw film is subjected to corona discharge treatment so that the surface tension is 43 dyn / cm, and the antifogging agent composition liquid is applied to the surface of the treated film with a Mayer bar (RD Specialties Company). Made by
No. It was applied in 6). Next, the film was dried in an oven at 70 ° C. for 1 minute.

The coating amount of the antifogging agent (converted value when dried) in the obtained antifogging agent-coated film was determined. Table 1 shows the results.
Shown in

Thus, an agricultural film was obtained.

Evaluation of Coating Film The coating film thus obtained was evaluated for coating uniformity, initial antifogging property, antifogging durability and transparency by the methods described below.

Regarding the coating uniformity, the appearance of the film was visually observed and evaluated according to the following criteria.

◯: The coated surface was almost uniform, ×: coating unevenness occurred.

Regarding the initial anti-fog property, water was put in a stainless steel water tank, the upper plane of the water tank was tilted by 10 degrees, and a film was spread on the upper end of the tank to adjust the water temperature to 10 ° C and the outside air temperature. Each film was kept at 0 ± 1 ° C., and the antifogging property of the film surface was visually observed 4 hours after the start of the test.

The evaluation was performed according to the following criteria.

5: Water film adhesion area was 100% of the whole, 4: Water film adhesion area was 80% of the whole 3: Water film adhesion area was 60% of the whole, 2: The water film adhesion area was 40% of the whole. 1: The water film adhesion area was 20% of the whole.

Regarding the anti-fogging durability, a film was similarly spread on the upper end of the above water tank, the water temperature was kept at 30 ° C. and the outside air temperature was kept at 10 ± 1 ° C., and one month after the start of the test, And the antifogging property of the film surface at each time point after the lapse of 4 months was visually observed.

The evaluation criteria are the same as in the case of the initial antifogging property.

Regarding the transparency, the total light transmittance (%) and haze (%) of the film were measured using a haze meter.

The evaluation results of the coated film are shown in Table 2.

Comparative Example 1 In the step of preparing the antifogging agent composition liquid, the amount of colloidal alumina used was 22 g, the amount of colloidal silica used was 22 g, and the amount of the nonionic surfactant aqueous solution used was 22 g. The same operation as in Example 1 was carried out except that the above was carried out to prepare an antifogging agent composition liquid having an antifogging agent concentration of 1% by weight.

In the coating process for the original film, a Mayer bar (RD Specialties) is used as a coating device.
Manufactured by No. In the same manner as in Example 1 except that 4) was used, the original film was coated with the antifogging agent composition liquid.

Except for the step of preparing the antifogging agent composition liquid and the step of coating the raw film, the same operations as in Example 1 were carried out and evaluated.

Example 2 In the step of preparing the antifogging agent composition liquid, the amount of the colloidal alumina used was 333 g, the amount of the colloidal silica used was 333 g, and the amount of the nonionic surfactant aqueous solution used was 333 g. Example 1 except that
In the same manner as above, an antifogging agent composition liquid having an antifogging agent concentration of 8% by weight was prepared.

Except for the step of preparing the antifogging agent composition liquid, the same operations as in Example 1 were carried out and the evaluation was carried out.

Comparative Example 2 In the step of preparing an antifogging agent composition liquid, 167 g of the above colloidal alumina was added to 1000 g of water, and this liquid was shaken in a synthetic resin bottle (internal volume: 2000 ml) for 1 minute.

The above liquid was added to the above colloidal silica 16
7 g was added, and the mixture was shaken in the bottle for 1 minute.

Further, 167 g of the above nonionic surfactant aqueous solution was added to the obtained liquid, and the mixture was shaken in the bottle for 1 minute, and the whole liquid was stirred to give an antifogging agent having an antifog concentration of 5.3% by weight. An agent composition liquid was prepared.

Except for the step of preparing the antifogging agent composition liquid, the same operations as in Example 1 were carried out and the evaluation was carried out.

Comparative Example 3 In the step of preparing the antifogging agent composition liquid, the amount of the colloidal alumina used was 598 g, the amount of the colloidal silica used was 598 g, and the amount of the nonionic surfactant aqueous solution used was 992 g. Example 1 except that
In the same manner as described above, an antifogging agent composition liquid having an antifogging agent concentration of 10% by weight was prepared.

Except for the step of preparing the antifogging agent composition liquid, the same operation as in Example 1 was carried out and the evaluation was carried out.

Comparative Example 4 In the step of preparing the antifogging agent composition liquid, the amount of the colloidal alumina used was 560 g, the amount of the colloidal silica used was 560 g, and the amount of the nonionic surfactant aqueous solution used was 560 g. Example 1 except that
In the same manner as described above, an antifogging agent composition liquid having an antifogging agent concentration of 10% by weight was prepared.

In the step of coating the original film, a Mayer bar (RD Specialties) is used as a coating device.
Manufactured by No. Example 1 except that 10) was used
The antifogging agent composition liquid was applied to the raw film in the same manner as in.

Except for the step of preparing the antifogging agent composition liquid and the step of applying it to the raw film, the same operations as in Example 1 were carried out and the evaluation was carried out.

Comparative Example 5 In the step of preparing the antifogging agent composition liquid, the amount of colloidal alumina used was 1430 g, the amount of colloidal silica used was 1430 g, and the amount of the nonionic surfactant aqueous solution used was 1430 g. The same operation as in Example 1 was carried out except that the above was adopted to prepare an antifogging agent composition liquid having an antifogging agent concentration of 13% by weight.

In the step of coating the original film, a Mayer bar (RD Specialties) is used as a coating device.
Manufactured by No. Example 1 except that 10) was used
The antifogging agent composition liquid was applied to the raw film in the same manner as in.

Except for the step of preparing the antifogging agent composition liquid and the step of applying it to the raw film, the same operations as in Example 1 were carried out and the evaluation was carried out.

[0083]

[Table 1]

[Table 2] As can be seen from the above table, it is recognized that the agricultural films obtained in Examples are superior in at least any of the items or at least as good as those in Comparative Examples.

[0084]

EFFECTS OF THE INVENTION According to the production method of the present invention, the use of an organic solvent is not required, the economical and handleability is excellent, and the antifogging agent composition liquid which has a long pot life is used. It is possible to provide an agricultural film pre-coated with an antifogging agent, which is excellent in antifogging property, antifogging durability and transparency.

Claims (2)

[Claims] 1. When forming an antifogging agent layer by applying an antifogging agent composition liquid on at least one surface of a thermoplastic synthetic resin film and drying it, a colloidal charged as mutually different charges is used as the antifogging agent composition liquid. Alumina and colloidal silica in a solid content weight ratio of 80 to 20:20 to 80.
From the inorganic colloid sol, which is mixed at a ratio of (total 100), the nonionic surfactant, and water,
A composition liquid prepared by mechanical shearing stirring and having a viscosity of 1 to 1000 mPa · s at room temperature is used to form an antifogging agent layer having an amount of the dry coating conversion of the antifogging agent of 0.05 to 1 g / m ^2. A method for producing an agricultural film, comprising: 2. An agricultural film having an increase rate of haze of 5% or less and a decrease rate of total light transmittance of 3% or less before and after formation of an antifogging agent layer. A method for producing the agricultural film described.