JPS5917735B2 - Agricultural polyethylene terephthalate film - Google Patents

Description

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

More specifically, over a long period of time. The purpose of the present invention is to provide an agricultural polyethylene terephthalate film that maintains excellent droplet flow properties and has excellent weather resistance. Generally, polyethylene terephthalate film exhibits high crystallinity, high melting point, heat resistance, and chemical resistance.

It is known to have excellent properties in terms of quality, strength, elastic modulus, etc., and is widely used for magnetic tape, photography, metallization, packaging, electricity, and agriculture. However, when the surface of the film is subjected to droplet treatment and used for agricultural purposes (e.g. hotbeds, buildings, etc.), the droplet flow properties deteriorate significantly within 3 to 6 months after the start of use. Water droplets adhere to the surface of the plant in granular form, reducing light transmittance and having a negative impact on crop growth. Conventionally, there has been a method of forming a film by adding various cationic, anionic, nonionic, or zwitterionic surfactants as droplet treatment agents into plastic materials, or by adding them to the film surface. A coating method and a method of coating or laminating a hydrophilic polymer on a film surface are known.

However, these methods 1) tend to volatilize or wash away, have poor sustainability of the droplet effect, 5 tend to attract dust, and significantly impede light transmittance;
3. If it is contained in a material, it will deteriorate the physical properties of the material when trying to give a sufficient droplet effect. 4. If it is coated or laminated on the film surface, it will not be sufficient. There are disadvantages such as poor adhesion between the film surface to which a drip effect is to be imparted and the coating layer (coating layer or laminate layer), and even if the adhesion is improved, a sufficient droplet effect cannot be obtained. 5 The droplet effect is related to the "wetting" of the film surface that comes into contact with moisture, and the better the droplet effect, the more hydrophilic the film is.

However, polyethylene terephthalate film is extremely hydrophobic, and even if the film surface is subjected to droplet treatment to form a hydrophilic droplet layer, the initial droplet effect is excellent. Adhesion of the droplet layer to the film surface is insufficient, and droplet persistence is poor. As a result of intensive research into a polyethylene terephthalate film that does not have such drawbacks and has a droplet effect, the inventors have found that a polyethylene terephthalate film having a film density of 1.390 V/c or less and oriented in at least one axis. On the film side of the terephthalate film, (a) a mixture of colloidal alumina, an anionic/or nonionic surfactant and water, or (b) a mixture of silicon tetrachloride, a monohydric aliphatic alcohol and an alkyl acetate. It was discovered that if droplet treatment is carried out using the film as a droplet treatment agent, the droplet effect will last, there will be less dust adhesion, no blocking will occur, and the physical properties of the film will not deteriorate, and the present invention has been achieved. did.

That is, the present invention provides a film having a density of 1,390 t/~ or less, oriented in at least one axis, and having (a) colloidal alumina, anionic and/or non-ionic alumina on at least one surface of the film. A droplet treatment is performed using a mixture of an ionic surfactant and water, or (b) a mixture of silicon tetrachloride, a monovalent aliphatic alcohol, and an alkyl acetate as a droplet treatment agent. This is agricultural polyethylene terephthalate 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). Other polymers that can be blended include polyamide,
Examples include polyolefins and other types of polyesters. Moreover, 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 1.390y/Cr.
It is at least uniaxially oriented (therefore,
It may be uniaxially oriented or biaxially oriented, but biaxially oriented is preferable.

) is a thing. The density of the film may be 1.390y/~ or less, but preferably 1.382y/CTit
It is more preferably 1.379y/ or less. If the density of the film is greater than 1.3907/~, the droplet persistence will be insufficient, which is not preferable. The means for orienting the film of the present invention is not particularly limited,
For example, any orientation means such as longitudinal uniaxial stretching, longitudinal and transverse biaxial stretching (sequentially or simultaneously), rolling, etc. may be employed.

The oriented film has a refractive index in the orientation direction (therefore, the refractive index in the longitudinal direction for uniaxial stretching in the longitudinal direction, and in the longitudinal and lateral directions for 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, and 1.55
The following are most preferred. Moreover, the oriented film further includes:
It is preferable that the elongation at break in at least one direction of the film can be maintained at 10% or more even after irradiation with a high-pressure mercury lamp having the strongest spectrum at 365 nm for 100 hours, and the elongation at break after the irradiation is 15%. The above are 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 break in at least one direction. It is preferable that the elongation can be maintained at 10% or more because it does not easily deteriorate even when exposed outdoors for a long period of time and exhibits extremely excellent weather resistance.

The polyethylene terephthalate film used in the present invention is, for example, melt-extruded at a normal extrusion temperature (260 to 330°C) and has an intrinsic viscosity [O (measured at 35°C using 0-chlorophenol as a solvent)] of 0.4 to 1. .0 polyethylene terephthalate unstretched film at a stretching temperature of 50 to 1
At 40°C, the stretching ratio is 2.0 to 5.5 times, preferably 3.
Stretch 0 to 4.5 times, and if necessary further stretch at 50 to 140°C
After stretching in a direction perpendicular to the stretching direction (if the stretching is in the longitudinal direction, then in the transverse direction) at a stretching ratio of 2.0 to 5.5 times, preferably 3.0 to 4.5 times, The obtained uniaxially oriented or biaxially oriented film was heated at 150°C or less for 1 to 10
It can be manufactured by heat setting for 0 seconds.

However, the polyethylene terephthalate used in the present invention
Films are not limited to those obtained by such methods. Polyethylene terephthalate used in the present invention
The film may have an appropriate thickness depending on its use.

Generally, those having a diameter of 1 μm to 2000 μm are often used. In the present invention, a droplet treatment is applied to the film surface of an oriented polyethylene terephthalate film having a film density of 1.3907/i or less.

When used in a greenhouse, etc., the moisture inside the greenhouse evaporates due to solar heat, condenses on the film surface inside the greenhouse, and adheres as water droplets, reducing the light transmittance of the film. This is to prevent adverse effects on the growth of crops. Therefore, it is usually sufficient to apply the droplet treatment to one of the front and back surfaces of the film, but the droplet treatment may be applied to both sides if necessary. In the present invention, the droplet treatment agent is (a) a mixture of colloidal alumina, anionic and/or nonionic surfactant and water or (b) silicon tetrachloride, monohydric aliphatic alcohol and alkyl acetate. Use a mixture.

Using such a droplet treatment agent has the advantage that less dust adheres to the film surface and does not cause blocking, and since less dust adheres, the droplet treatment agent on the film surface is less likely to be lost along with the dust. The persistence of the droplet effect increases. In the mixture (a), the surfactant is used to improve wetting of the film surface when the mixture is applied to the film surface, and the active ingredient for the droplet effect is colloidal alumina.

The colloidal alumina preferably has a small particle size, and usually has an average particle size of 100 mμ or less, especially 50 mμ.
It is preferable to use a material less than μ. The average particle size referred to here is the maximum diameter in a certain direction (
You can measure the so-called green diameter) and use the average value. For the droplet treatment, 0.1 to 1.0% by weight (particularly preferably 0.125 to 0.5% by weight) of colloidal alumina, anionic and/or nonionic, based on the entire dispersion. The surfactant content is 0.001 to 0.5% by weight (
A dispersion liquid having a composition of particularly preferably 0.002 to 0.2% by weight) is prepared, and this is applied to the film surface and heated and dried (
Preferably, the temperature may be heated to 71° C. or higher). The amount of colloidal alumina to be applied to the film surface is preferably such that 10 -6 to 10 -3 y of colloidal alumina is deposited per 1 cd of the film. Any surfactant can be used, and representative examples include sulfuric ester salts for anionic surfactants, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene alkyl ester for nonionic surfactants. Examples include phenyl ether. In the case of the mixture (b) above, based on the total weight of silicon tetrachloride, monohydric aliphatic alcohol, and alkyl acetate,
Silicon tetrachloride is 1 to 7% by weight (particularly preferably 1 to 5% by weight), monohydric aliphatic alcohol is 30 to 70% by weight (particularly preferably 40 to 60% by weight), and the remainder is alkyl acetate. is preferred. The mixture may contain a small amount of water to partially hydrolyze the silicon tetrachloride. Any monohydric aliphatic alcohol can be used, but alcohols having 6 or less carbon atoms, especially methyl alcohol, ethyl alcohol,
Propyl alcohol, allyl alcohol, etc. are preferably used.

Further, any alkyl acetate can be used, but the number of carbon atoms is 6.
The following esters of alkyl groups and acetic acid are preferably used, particularly methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and the like. The amount of coating on the film surface is determined by applying and drying.
The thickness of the coating formed on the film surface is 0.05 to 50μ
It is preferable to do so. When the mixture is applied to the film surface and dried, a silicon compound film is formed under the action of moisture in the air, and the film exhibits a droplet effect. Drying may be natural drying, heat drying, or heat drying. To apply these droplet treatment agents to the film surface, any coating method such as a gravure roll coater, an air doctor flade coater, a scratch coater, a Mayer bar coater, etc., or a spray method or a casting method can be used. means can be adopted. 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 droplet treatment, or the surface that is not subjected to the droplet treatment is coated, or a UV inhibitor is contained together with the droplet-forming substance. 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 droplet treatment.

In the present invention, an oriented film with a density of 1.390 t/~ or less, which is lower than normal films, is used, so the weather resistance of the film is excellent and its service life is increased, and the adhesion of the droplet treatment agent to the film is also improved. It also has the advantage of significantly improving the sustainability of the droplet effect.

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.

1. Tensile test Using Tensilon UTM-1500 manufactured by Toyo Port Win Co., Ltd., at room temperature and relative humidity of 65%, the length was 10 CT.
! A load/elongation chart was prepared by pulling an original film with a width of 100% and a width of 1 yen, and each value was determined by calculation.

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

3. Refractive index D of Na, measured at 25°C using an Atsube 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
．． Mark the distance between the gauges on the heat shrinkage film so that it is 30CTIL, and after exposing it to hot air at 120'C for 1 minute, measure the distance between the gauges and calculate the distance between the gauges relative 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 H4OO-P type manufactured by Tokyo Shibaura Electric Co., Ltd.) (using a 100V power supply)
, 20? from a rod source? A weather resistance test was conducted by arranging the films in parallel at separate positions and irradiating the film surface for a predetermined period of time.

The H4OO-P photochemical mercury lamp has the following operating characteristics.

′、． Evaluation method for evaluation of droplet properties () Droplet persistence test: Set the water temperature in a constant temperature water bath to 50°C ± 2°C, cover it with a droplet treatment film, and make a completely sealed system with tape or the like.

The droplet treated film was 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 () Water resistance test: After exposing the treated surface (50cm x 50 cm square) to running water (approximately 41/Mm of tap water) for 4 hours, it was subjected to the droplet persistence test of evaluation method (), and the droplet resistance was evaluated for 2 hours. This is a more severe test than evaluation method (1) in which the area of the retained area is measured.
) is useful for relative evaluation of samples without superiority or inferiority.

Evaluation method (): Evaluation was conducted through a practical test for 6 months by deploying the product in an actual greenhouse (area: 14rr1) and maintaining the minimum temperature inside the greenhouse at 10°C to 15°C, including the winter season.

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

Examples 1 to 3 and Comparative Examples 1 to 2 Polyethylene terephthalate (intrinsic viscosity of 0.65 measured at 25°C using 0-chlorophenol as a solvent) chips were dried and melt-extruded in a conventional manner to obtain a thick Sa1
A 100 μm unstretched film was obtained.

The unstretched film was stretched in the machine direction at a temperature of 65°C and a stretching ratio of 3.2 times, and then in the transverse direction at a temperature of 65°C and a stretching ratio of 3.

Sequential biaxial stretching at 4x and 10x at the specified temperature (see Table 1)
Heat set for seconds to form a biaxially oriented film with a thickness of 100 μY (Examples 1 to 3).

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 obtain a bidirectionally oriented film with a thickness of 100 μm (Comparative Examples 1 and 2). Table 1 shows the heat shrinkage rates (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, it can be seen that films of 07/i and below have much better weather resistance than other films. Next, the surface of the film shown in Table 1 was subjected to droplet treatment, and the droplet flow properties were evaluated.

(Example 1) On one side of the film of Example 1 shown in Table 1, colloidal alumina (average particle size 30 mμ) 107 and nonionic surfactant (NS-210 manufactured by NOF K.K.
) 27, silicone emulsion (antifoaming agent) 0.
A colloidal alumina dispersion obtained by thoroughly stirring and mixing 057 and water 907 was diluted by adding water 39807, and the resulting solution was sprayed to give a concentration of 0.2 per m2 of film surface.
5y of colloidal alumina was deposited, dried at room temperature, and subjected to evaluation.

(Example 2) One side of the film of Example 2 shown in Table 1 (same as that of Example 1) was coated with 1.8
% by weight, 25.2% by weight of methyl alcohol, 23% by weight of methyl acetate, and 50% by weight of methyl ethyl ketone. The coating was applied with a gravure roll coater, and the coated surface was dried with hot air at 100°C for 3 minutes while the film surface that was not coated with the liquid was in contact with the drum surface at 40°C to form a coating film with a thickness of 2 μm. provided.

(Example 3) The film of Example 3 shown in Table 1 was subjected to the same droplet treatment as in Example 1 and was subjected to evaluation.

(Comparative Example 1) The film of Comparative Example 1 shown in Table 1 was subjected to the same droplet treatment as in Example 1 and subjected to evaluation.

(Comparative Example 2) The film of Comparative Example 2 shown in Table 1 (same as that of Comparative Example 1) was subjected to the same droplet treatment as in Example 2 and subjected to evaluation.

Table 2 shows the results of evaluating the droplet properties of the above droplet treated film.

3. From the results in Table 2, it can be seen that the film of the present invention has much better droplet persistence and water resistance than conventional films.

In addition, when the droplet treated films of Examples 1 to 3 were spread over a length of 10 m on a greenhouse frame having a metal frame with an inter-frame distance of 50 CTL, it was not completely tensioned and some slack remained. , about 2% of the actual length
A little extra film was needed.

When the stretched film was exposed to the sun, the sagging was significantly reduced after just one day's worth of sunlight, and a taut state was created.
As a result, there was no flapping due to rain, wind, etc., and there was no damage or loss of dripping properties for over a year. On the other hand, in the greenhouse in which the film of Comparative Example 1 was spread, the film did not stay under tension forever, remained sagging, and broke after about 3 months.

Claims (1)

[Claims] 1 A film having a density of 1.390 g/cm^3 or less, oriented in at least one axis, and containing (a) colloidal alumina, anionic and/or nonionic surfactant and 1. A polyethylene terephthalate film for agricultural use, characterized in that it has been subjected to a droplet treatment using a mixture of water or (b) a mixture of silicon tetrachloride, a monovalent aliphatic alcohol, and an alkyl acetate as a water droplet prevention treatment agent.