JPS5838303B2 - Agricultural polyethylene terephthalate film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to agricultural polyethylene terephthalate films.

More specifically, the present invention aims to provide an agricultural polyethylene terephthalate film that maintains excellent drip-free properties over a long period of time and has excellent weather resistance.

In general, polyethylene terephthalate film exhibits high crystallinity and high melting point, and is known to have excellent properties such as heat resistance, chemical resistance, strength, and elastic modulus, and is used for magnetic tapes and photographs. It is widely used for metallization, packaging, electricity and agriculture.

However, when the surface of the film is treated with a droplet-free treatment and used for agricultural purposes (e.g. hotbeds, vinyl greenhouses, etc.), the drop-free property deteriorates significantly after 3 to 6 months after the start of use, and water droplets form on the inner surface of the film. If it adheres to the surface, the light transmittance will decrease, and it will have a negative effect on the growth of the actuator.

Drop-free effect involves "wetting" of the film surface that comes into contact with moisture.
The better the droplet-free effect, the more hydrophilic it is, but polyethylene terephthalate film is extremely hydrophobic.

Therefore, even if a hydrophilic dropless layer is formed by applying a droplet-free treatment to the film surface, the adhesion of the droplet-free layer to the film surface is insufficient, although the initial dropless effect is excellent. However, this method has the disadvantage of poor drip-free durability.

In order to solve these drawbacks, the inventors of the present invention have conducted extensive research and found that the density of the film is 1. If dropless treatment is applied to the film surface of a polyethylene terephthalate film oriented in at least one axis at 390 y/crA or less, the dropless layer will adhere well to the film surface and the dropless persistence will be significantly increased. We have discovered that this is the case, and have arrived at the present invention.

That is, in the present invention, the film density is 1.390? /crt
The following describes an agricultural polyethylene terephthalate film that is oriented in at least one axis and is subjected to a dropless treatment on one or both sides of the film.

The polyethylene terephthalate referred to in the present invention includes not only non-copolymerized polyethylene terephthalate and homopolymer, but also copolymerized polyethylene terephthalate in which 85% or more of the repeating units are ethylene terephthalate units and the remainder is other components, Polyethylene terephthalate is 85% by weight or more (preferably 90% by weight)
or more) and other polymers account for 15% by weight or less (preferably 10% by weight or less).

Examples of other polymers that can be blended include polyamides, polyolefins, and other types of polyesters.

Further, the polyethylene terephthalate may contain a lubricant, a matting agent, a coloring agent, a stabilizer, an antioxidant, etc. as necessary.

The polyethylene terephthalate film used in the present invention has a density of 1.39 Cl/1 or less and is oriented in at least one axis (therefore, it may be uniaxially or biaxially oriented, but biaxially oriented is preferred.

) is a thing. The density of the film is 1. ．． It may be 390 g/1 or less, preferably 1.382 g/1 or less, more preferably 1.379 g/1 or less.

The density of the film is 1.39o? /C7ft is not preferable because the drip-free durability is insufficient.

The means for orienting the film of the present invention is not particularly limited.
Or simultaneously), any orientation means such as rolling may be employed.

The oriented film has a refractive index in the orientation direction (therefore, the refractive index in the longitudinal direction for longitudinal coaxial stretching, and in the longitudinal and transverse directions for longitudinal and lateral biaxial stretching) of 1.57 or more, particularly 1.59 or more. is preferred.

Most preferably, the refractive index is 1.61 or more.

Furthermore, the refractive index of the film in the thickness direction is preferably 1.57 or less.

The refractive index is particularly preferably 1.56 or less, most preferably 1.55 or less.

Further, the oriented film is preferably one that can maintain the elongation at break in at least one direction of the film at 10% or more even when irradiated for 100 hours with a high-pressure mercury lamp having the strongest spectrum at 365 nm. Breaking elongation is 15
% or more is particularly preferred.

The oriented film has a refractive index in the orientation direction of 1.57 or more and a refractive index in the thickness direction of 1.57 or less, and even if irradiated with the high-pressure mercury lamp for 100 hours, the film does not elongate at break in at least one direction. A material that can maintain a temperature of 10% or more is preferable because it does not easily deteriorate even when exposed outdoors for a long period of time and exhibits excellent weather resistance.

The polyethylene terephthalate film used in the present invention is, for example, melt-extruded at a normal extrusion temperature (260 to 380°C), and has an intrinsic viscosity [η] (measured at 35°C using 0-chlorophenol as a solvent) or 0.4°C. ~1.0 polyethylene terephthalate unstretched film at a stretching temperature of 50~
At 140°C, the stretching ratio is 20 to 55 times, preferably 3.0
Stretch to ~4.5 times and further stretch at 50~140'C if necessary
The obtained uniaxial 1 to 100% of oriented or biaxially oriented film at 150°C or less
It can be manufactured by heat fixing for seconds.

However, the polyethylene terephthalate used in the present invention
The film I1 is not limited to those obtained by such a method.

The polyethylene terephthalate film used in the present invention may have an appropriate thickness depending on its use.

Generally, 1μ to 2000μ is often used.

In the present invention, a dropless treatment is applied to the film surface of an oriented polyethylene terephthalate film having a film density of 1.390 S'/1 or less.

When used in a greenhouse, etc., the moisture in the greenhouse evaporates due to solar heat, resulting in green...
This is to prevent water droplets from condensing and adhering to the film surface inside the cage, reducing the light transmittance of the film and adversely affecting the growth of the work.

Therefore, it is usually sufficient to perform a dropless treatment on one side of both the front and back surfaces of the film, but if necessary, a dropless treatment may be applied to both sides.

To perform the dropless treatment, a solution containing a dropless substance may be applied to the film surface.

The dropless material can be any material used for dropless treatment of the film surface, but usually various hydrophilic polymers, such as polyester made by polycondensation of dibasic acid and polyethylene glycol, N-methoxymethyl A mixture of nylon and water-soluble methoxymethylolated melamine, a mixture of a copolymer of acrylic acid ester and hydroxyacrylic ester with a surfactant, polyvinyl alcohol, α
・β-monounsaturated carboxylic acids (e.g. maleic acid, fumaric acid, itaconic acid, etc.) or acrylic acid/methacrylic acid, etc. and acrylic acid derivatives (e.g. acrylic esters, acryl amide, etc.) ・Methacrylic acid derivatives (e.g. methanelylic acid esters) , methacrylic acid amide, etc.), acrylonitrile, vinyl acetate, and/or copolymers with styrene maleate, etc. are often used.

In addition to the dropless substance, the dropless treatment liquid contains various additives such as a coating film hardening agent, a hydrophilic agent, a flow regulator, a viscosity regulator, a curing accelerator, a neutralizing agent, etc., as necessary. may be added.

The coating film curing agent is used to harden the coating film and give the persistence and effect stability of the non-droplet material.Usually, polyepoxide is added in an amount of 0.5 to 5% by weight per one of the above-mentioned non-droplet material. It is recommended to add %.

Hydrophilic additives are added to appropriately adjust the hydrophilicity of non-droplet materials by increasing or decreasing them, improving adhesion and cohesive force, plasticizing, and adjusting coating film hardness and viscosity. For example, oily or waxy surfactants (
nonionic type, anionic type, etc.), water-soluble plasticizers such as polyester polyols, polyether polyols, glycerin, etc., inorganic electrolytes such as polyacrylic acid, polyacrylamide, potassium acetate, ammonium acetate, potassium chloride, rotankali, etc. are often used. It will be done.

The processing agent (solid content) concentration in the dropless processing liquid is usually 0.01~
It is assumed to be 5% by weight.

Further, as a solvent, water, an organic solvent miscible with water, or a mixture thereof is usually used.

As for the coating method, any coating method can be adopted, such as using a gravure roll coater, an air doctor, a flade coater, a kiss coater, a Mayer bar coater, or using a soufflé method or a casting method.

The coating film thickness (after drying) is preferably about 0.01 to 100 μm.

Drying after application of the treatment liquid may be performed by natural drying or heat drying.

If necessary, the film of the present invention may contain an ultraviolet inhibitor in the base film or may be coated on the film surface within a range that does not adversely affect the growth of plants.

When coating, the film surface is coated with an ultraviolet absorber in advance before the non-droplet treatment is applied, or the surface that is not subjected to the droplet-free treatment is coated, or an ultraviolet inhibitor is contained together with the non-droplet material. Preferably, the solution is applied to the film surface.

The film of the present invention may also be processed by laminating another film or a polyethylene terephthalate film with different physical properties on the side that is not subjected to the dropless treatment.

The film of the present invention can be used, for example, for cultivating horticultural crops such as vegetables, flowers, fruit trees, etc., agricultural crops such as paddy rice, tobacco, etc., for mulching, for silos, or for spreading in greenhouses, tunnels, etc., or as curtains in greenhouses. etc., are widely used for agricultural purposes.

Below, methods for measuring the main physical properties used in the present invention will be shown.

■． Tensile test Tensilon UTMIII-50 manufactured by Toyo Baldwin Co., Ltd.
Using type 0, the length is 10 at room temperature and relative humidity 65%.
crrL1 width 1 crrL original film 100%/mi
A load-elongation chart was prepared under tension at n, and each value was determined by calculation.

Elongation at break: The elongation relative to the original length at break is expressed in %.

Breaking strength - The force required to break a film at room temperature is expressed as the force (kg/m4) applied per unit cross-sectional area of the original film.

2. Density This is a value measured by the float-sink method in a mixed solvent of n-hebutane and carbon tetrachloride at 25°C.

3. Refractive index NaOD, measured at 25°C using an Appe refractometer
Indicates the value for the line.

Although the refractive index often changes in the width direction of the film, the value adopted in the present invention is the maximum value of the refractive index.

4. Marks are placed on the heat shrinkage film so that the distance between the gauges is 30 crrL, and after exposing it to hot air at 120°C for 2 minutes, the distance between the gauges is measured, and the distance between the gauges is compared to the initial distance between the gauges. The rate (%) of the decrease in the gauge distance was determined, and this rate was taken as the heat shrinkage rate.

5. Weather resistance test using a high-pressure mercury lamp (photochemical mercury lamp H400-P type manufactured by Tokyo Shibaura Electric Co., Ltd.) (using a 100V power supply)
A weather resistance test was conducted by placing the film in parallel at a distance of 20 C-rrL from a rod-shaped radiation source and irradiating the film surface for a predetermined period of time.

The H400-P photochemical mercury lamp has the following operating characteristics.

Total length: 2. 95 mm Tube diameter: 18.5 mm Lamp power: 400 W Lamp voltage: 130 V Lamp current: 3.3 A Arc length: 150 mm Shine: 200 cd/crA Strongest spectrum: 365n Door radiation limit: 220 nm 6. Drop-free evaluation evaluation method (I) Drop-free persistence test: The water temperature in the constant temperature water tank was set to 50
Set the temperature to ±2°C, cover with a dropless film, and use tape to completely seal the system.

The dropless treated film is set at a 30 degree inclination* using a support provided at the edge of the constant temperature water bath.

Sustainability was expressed as the time until the effect partially disappeared.

Evaluation method (n) Water resistance test: Treated surface (50 x 50 crr
L square) was exposed to running water (approximately 4 g/mm of tap water) for 4 hours and then subjected to the dropless persistence test of evaluation method (I).
The area that remained drip-free for 2 hours was measured.

This is a more severe test than evaluation method (I), and is useful for relative evaluation of samples that cannot be distinguished by evaluation method (I).

Hereinafter, the present invention will be explained in detail with reference to Examples.

Examples 1 to 2 and Comparative Example 1 Polyethylene terephthalate (intrinsic viscosity measured at 35°C using o-chlorophenol as a solvent is 0.65)
The chips were dried and melt-extruded in a conventional manner to obtain an unstretched film with a thickness of 1100 μm.

The unstretched film was stretched in the machine direction at a temperature of 65°C and a stretching ratio of 32 times, and then in the transverse direction at a temperature of 65°C and a stretching ratio of 3.
．． Sequential biaxial stretching at 4 times, 1 at specified temperature (see Table 1)
It was heat-set for 0 seconds to form a biaxially oriented film with a thickness of 100 μm (Examples 1 and 2).

On the other hand, for comparison, the unstretched film was sequentially biaxially stretched in the longitudinal direction at a stretching temperature of 90°C and a stretching ratio of 3.2 times, and then in the transverse direction at a stretching temperature of 110°C and a stretching ratio of 3.4 times.
It was heat-set at ℃ for 10 seconds to form a biaxially oriented film with a thickness of 100 μm (Comparative Example 1).

Table 1 shows the heat shrinkage rate (120° C., 1 minute value) and weather resistance test results of these biaxially oriented films.

From the results in Table 1, the film density used in the present invention is 1.39.
(According to an accelerated deterioration test using a high-pressure mercury lamp, a film with a size of 1/1 or less was found to have much better weather resistance than a film with a size of 1/1 or less.

After the surface of the biaxially oriented film produced by the above method is subjected to corona discharge treatment, the film surface is coated with a degree of saponification of 98.
5±5 mol% of holivinyl alcohol (trade name: Shin-Etsu Poval C-17 is used) is dissolved in hot water to make a 1% by weight aqueous solution, and after cooling, nonionic surfactant MS-210 (NOF K-K) is dissolved in hot water. A dropless treatment solution prepared by adding 2% by weight of the product) was applied using a gravure roll coater so that the dry coating amount was 0.4P/m, and the surface to which the treatment solution was not applied was heated at 40°C. The coated surface was dried with hot air at 100° C. for 3 minutes while in contact with the drum surface.

Table 2 shows the results of the dropless durability test and water resistance test of the obtained film.

From the results in Table 2, it can be seen that the drop-free persistence and water resistance of the film of the present invention are significantly superior to those of other films.

In addition, when the dropless treated films of Examples 1 and 2 were spread over a length of Ion on a greenhouse frame having a metal frame with a distance between frames of 50 crrL,
It has not been completely tensioned and there is some slack left, and it is about 2 times shorter than the actual length.
A little less than % more film was required.

When the stretched film was exposed to the sun, the sagging was significantly reduced after just one day's worth of sunlight, and the film could be stretched to a taut state.

As a result, there was little flapping due to rain, wind, etc., and there was no damage or loss of drip-free properties for over a year.

On the other hand, in the clean house where the film of Comparative Example 1 was spread, the film did not stay under tension forever, remained sagging, and broke after about 3 months.

In addition, the non-dripability began to deteriorate significantly after about 3 months.

Claims (1)

[Claims] 1 Film density is 1. 390? 1. A polyethylene terephthalate film for agricultural use, characterized in that it is oriented in at least one axial direction under the axial direction, and is subjected to a dropless treatment on one or both sides of the film.