JPH0873620A - Fluororesin film - Google Patents

Abstract

PURPOSE: To obtain a fluororesin film differing in the roughness of both surfaces from each other, consisting mainly of a fluororesin, excellent in stainproofness, adhesivity, drip-proofness, durability and light-transmissivity, and useful as an antifouling sheet, tent, etc. CONSTITUTION: This fluororesin film consists mainly of pref. an ethylene- tetrafluoroethylene copolymer, having the following characteristics: the surface roughness (Ra1 ) of one side (A-surface) of the film and that (Ra2 ) of the other side (B-surface) are interrelated as Ra1 >Ra2 [pref. (Ra1 -Ra2 )>=0.002μm]; and the difference in the number of projections 20-200μm in height on the A-surface (P1 ) and B-surface (P2 ):(P1 -P2 ) stands at pref. >=5.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fluororesin film. Specifically, the present invention relates to a fluororesin film having surfaces having different surface morphologies.

[0002]

2. Description of the Related Art Fluororesin films are used for various purposes because they have excellent heat resistance, weather resistance, chemical resistance, electric insulation and the like. Among them, since it has the best weather resistance and antifouling property among plastics, it is suitable as a surface protective material for various base materials and a covering material for agricultural houses. However, when it is applied outdoors as a surface protection material, the fluororesin film is more likely to adhere more firmly to various base materials such as plastic as a material to be protected, and on the other hand, it is difficult for dust and dirt to adhere due to long-term exposure. Conflicting surface properties are required. Also, when applied to a covering material for agricultural houses, similarly, it is preferable to have a surface having different surface characteristics in terms of not only antifouling property but also adhesion of a drip-proof layer formed on the surface, durability, etc. obtain.

Therefore, as a film having such a function on the surface thereof, there is known a fluororesin film whose surface is subjected to surface treatment such as corona discharge treatment.

[0004]

However, in the conventional fluororesin film, there were concerns about the existence of non-uniform portions of the treatment on the surface and the durability of the treatment effect. Furthermore,
Even if the surface treatment is applied, there is a point that the balance between the antifouling property and the adhesive property is not sufficient because the morphology on both surfaces of the film is similar. That is, it was not possible to satisfy the two conditions of the film surface being rougher from the adhesive surface and smoother from the antifouling surface.

The present invention solves the above problems,
It is an object of the present invention to provide a fluororesin film that is highly durable and has excellent antifouling properties and adhesiveness as a fluororesin film.

[0006]

The fluororesin film of the present invention for this purpose is a film containing a fluororesin as a main component, and has a surface average roughness (Ra) of one surface (A surface) of the film. ₁ ) and the surface average roughness (Ra ₂ ) of the other surface (B surface) have a relationship of Ra ₁ > Ra ₂ .

In the present invention, the material of the fluororesin is not particularly limited, and various known materials can be used.
Typical examples include tetrafluoroethylene polymer, ethylene-4fluoroethylene copolymer, tetrafluoroethylene-6fluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and 2 Examples thereof include vinylidene chloride polymer, trifluoroethylene polymer, monofluoroethylene polymer, chlorotrifluoroethylene polymer and the like, and copolymers and mixtures thereof. However, it is preferable to use a tetrafluoroethylene-6-fluoropropylene copolymer or an ethylene-4fluoroethylene copolymer from the aspects of mechanical properties, film-forming property, processability, etc. Those containing a copolymer as a main component are particularly preferable. The main component is preferably 50% or more, more preferably 70% or more of the resin component itself, and may appropriately contain other substances.
The resin to be added is not particularly limited, but examples thereof include a polyolefin resin and an acrylic resin.

In addition, known additives such as heat resistance stabilizers, oxidation resistance stabilizers, weather resistance stabilizers, UV absorbers and antistatic agents may be added to the fluororesin in an amount that does not impair the effects of the present invention. Agents, pigments, dyes, inorganic or organic fine particles, dispersants, coupling agents, fillers and the like may be added.

Further, the fluororesin film of the present invention may be used in any of unoriented, uniaxially oriented and biaxially oriented, but when mechanical strength is required, the oriented film is desirable.

The thickness of the fluororesin film is not particularly limited, and an appropriate thickness can be set within the range of about 1 to 500 μm. Further, the mechanical characteristics and optical characteristics of the fluororesin film are not particularly limited, and can be appropriately set to desired values in consideration of required characteristics for various applications.

Further, in the present invention, one surface (A surface) of the film may be subjected to a surface treatment in order to impart further easy adhesion to the fluororesin film and improve processability. Examples of the surface treatment include known methods such as corona discharge treatment (in air, nitrogen, carbon dioxide gas), plasma treatment (high pressure and low pressure), alkali metal solution treatment, high frequency sputter etching treatment and the like.

The treatment strength is not particularly limited and can be appropriately set to a desired value according to the application. As a measure of the treatment strength, the surface wetting index of the film measured according to JIS-K-6768 is used. It is preferably 40 dyn / cm or more, and more preferably 45 dyn / cm or more.

In the present invention, in order to achieve the object of the present invention, one surface of the fluororesin film surface (A surface)
It is necessary to average surface roughness (Ra ₁₎ and the surface roughness of the other surface (B surface) (Ra ₂₎ and the Ra _1> Ra ₂ the relationship.

In the present invention, the surface average roughness of the fluororesin film is not particularly limited, but from the viewpoint of the effect obtained, the surface average roughness Ra ₁ is 0.01 μm or more, preferably 0.015 μm or more. The average surface roughness Ra ₂ is less than 0.01 μm, preferably less than 0.01 μm.
It is preferably less than 008 μm.

Further, in the present invention, the difference between the average surface roughness Ra ₁ and Ra ₂ is 0.002 μm or more, preferably 0.002 μm or more.
Those having a thickness of 5 μm or more, more preferably 0.008 μm or more are more desirable in terms of functions such as antifouling property and easy adhesion.

Further, in the present invention, the height A of the surface 20 is 20.
The number of protrusions P _{1 of up} to 200 mμ and the height of the B surface 20 to 200 m
it is preferred that the projection number P ₂ of μ is the P ₁ -P ₂ ≧ 5 the relationship, more preferably P ₁ -P ₂ ≧ 10, more preferably from P ₁ -P ₂ ≧ 20. If the difference in the number of protrusions on both surfaces is less than 5, problems may occur in the slipperiness between the film surfaces, or the antifouling property and the adhesive property may not be balanced.

The formation of the predetermined surface defined in the present invention can be achieved by the well-known technique, for example, the lamination method using inorganic particles, but it is added in the fluororesin film. It is difficult to apply general inorganic particles to corrosive gas generated when the fluororesin is melted, which causes a problem of discoloration and deterioration. Therefore,
It is desirable to obtain the desired surface in a substantially particle free form. As the method, some technique at the time of extrusion molding processing, for example, adoption of electrostatic application method, adjustment of cooling rate of surface layer by blowing hot air, change of surface roughness of cast drum surface and combination thereof, Preferably
In particular, the combined use of the electrostatic application method and the hot air blowing method is preferable.

In the present invention, when the film of the present invention is applied to an agricultural house, it is desirable to form a drip-proof layer on one surface (A surface) of the film. Generally, a drip-proof layer is required for a coating material for a house because water vapor scattered from soil and plants aggregates on the inner surface of the house to form fine water droplets, which cause various harmful effects such as deterioration of light transmittance. It is said that As the drip-proof layer, known ones disclosed as drip-proof agents can be applied, and normally, those having a new aqueous polymer, a surfactant, colloidal silica, alumina sol or the like and various mixtures thereof as a main component are usable. It can be preferably used.

Further, in the agricultural house, especially in facility cultivation from late autumn to winter, fog is generated in the vicinity of the inner surface of the covering material in the morning or the evening when the temperature difference from the outside air is apt to drastically change, Moreover, natural convection causes a phenomenon of covering the whole area of the house. However, the generated fog wets leaves, stems, flowers, fruits, etc. of cultivated crops and causes diseases, and disadvantages such as poor growth due to insufficient light transmission and heating fuel consumption to dry the cultivated crops. Therefore, it is desirable that the anti-fog agent is contained in the drip-proof layer. As the anti-fog agent, known ones can be applied, but of these, an organic fluorine surfactant is preferable. Examples of the organic fluorine-based surfactant include those containing a linear or branched perfluoroalkyl group or a perfluoroalkenyl group, an anionic surfactant,
At least one selected from cationic surfactants, amphoteric surfactants, nonionic surfactants and the like is applied.

The drip-proof layer may further contain known additives such as defoaming agents, coatability improvers, antioxidants, dyes, if necessary.
A pigment or the like may be included. The layer thickness of the drip-proof layer is not particularly limited, but is 0.01 to 5.0.
μm is preferable, and more preferably 0.05 to 1.0 μm.
Those in the range are preferable in terms of uniform layer forming property, handleability, drip-proof property and the like.

Next, a method for producing the film of the present invention will be described, but the invention is not limited to such an example.

First, the raw material pellets obtained by a conventional method are fed to a melt extruder, and melt-extruded into a sheet form from a slit die at a temperature not lower than the melting temperature of the pellets and not higher than the temperature at which the resin decomposes. It adheres on a cooling drum of ~ 250 ° C by an electrostatic application method. Subsequently, hot air with a temperature of 50 to 400 ° C. is applied to the sheet surface in a state of being in close contact with the drum on a scale of 1 to 1.
After spraying for 20 seconds, it is cooled and solidified to prepare an unstretched film. Further, the unstretched film may be uniaxially or biaxially stretched by a known simultaneous biaxial or sequential stretching method, if necessary, or may be subjected to a known discharge treatment such as corona discharge treatment in various atmospheres. . Next, as a method of providing a drip-proof layer on the film surface, a method of applying a solution adjusted to a predetermined amount to a film to be a base in a film-forming step, followed by drying, after winding as a base film single film ,
A method of providing a coating-drying step can be preferably applied. The coating method is not particularly limited, and may be an extrusion laminating method, a melt coating method, or the like, but a gravure coating method, a reverse coating method, a kiss coating method, a die coating method, because it is possible to coat a thin film at a high speed. A known method such as a metalling bar coating method can be applied. Further, the coating material concentration and the coating film drying conditions are not particularly limited, but it is desirable that the coating film drying conditions be carried out within a range that does not adversely affect various characteristics of the base film.

[0023]

[Characteristic Measuring Method and Evaluation Method] The characteristic value of the present invention is based on the following measuring method and evaluation criteria.

(1) Surface average roughness (Ra ₁ , Ra ₂ ) It was measured using a three-dimensional surface roughness meter (manufactured by Kosaka Laboratory Ltd.).

(2) Number of protrusions (P ₁ , P ₂ ) The same equipment as in (1) above was used. As for the number of protrusions, one peak count level is provided at a level parallel to the center line of the obtained roughness curve and separated by + y, and the upper peak count intersects between two points where the curve intersects the center line. When a point exists one or more times, it is determined as one peak and the number of peaks is determined within a measurement length of 1 mm.

(3) Easy-adhesion property A vapor-deposited aluminum layer having a thickness of about 300 Å is formed on the surface of the film, and "Cellotape" CT- is formed on the aluminum layer.
No. 24 (manufactured by Nichiban Co., Ltd.) was adhered and pressure-bonded with a hand roller, and then “Cellotape” was forcibly peeled in the direction of 180 °, and the degree of peeling of the aluminum layer was observed and judged as follows.

◯: Good (peeling area less than 5%) Δ: Slightly inferior (peeling area 5% or more and less than 20%) X: Poor (peeling area 20% or more) (4) Drip-proof property 30 tsubo steel house (under eaves) 2.5m, roof slope 15
The surface A of the film was coated on the inner surface of the film, and the drip-proof property was visually observed for 6 months in winter (October to March) under crop cultivation, and the following judgment was made.

◯: Good Δ: Slightly inferior ×: Poor (5) Antifouling property (3) Film was spread on the roof part of the house with the B side of the film outside, and the degree of dust attached to the outer surface of the covering material was measured with time. Comparative observations were made and evaluation was made according to the following criteria.

◯: Good Δ: Slightly bad ×: Bad

[0030]

The present invention will be described with reference to the following examples and comparative examples, but the present invention is not limited thereto.

Example 1 ETFE pellets "NEOFLON" EP521 (manufactured by Daikin Industries, Ltd.) was supplied to an extruder and then fed at 295 ° C by a conventional method.
And melt-extruding the molten sheet on a cooling drum kept at a surface temperature of 160 ° C. by an electrostatic application method, blowing hot air at a temperature of 190 ° C. on the surface of the sheet for about 20 seconds, and then cooling and solidifying it to obtain a thick film. An unstretched film having a size of 50 μm was obtained.
The properties of the obtained fluororesin film are as shown in Table 1, and the film had excellent properties because the surface average roughness of the non-drum surface was larger than that of the drum surface.

Example 2 Based on Example 1, after closely adhering by the electrostatic application method as in Example 1, hot air at a temperature of 250 ° C. was applied to the surface of the sheet for about 15 minutes.
After spraying for 2 seconds, an unstretched film having a thickness of 100 μm was obtained in the same manner. As shown in Table 1, it can be seen that the fluororesin film is excellent in each property.

Example 3 The surface A (non-drum surface) of the fluororesin film obtained in Example 1 was subjected to corona discharge treatment in air at a treatment strength of 80 W · min / m ² , and then the treated surface was treated. Polyvinyl alcohol “Dencapovar” K-24E (manufactured by Denki Kagaku Kogyo Co., Ltd.) and colloidal silica (Catalyst Kasei Kogyo Co., Ltd.)
Manufactured), nonionic surfactant "NONION" NS-210
(Nippon Yushi Kogyo Co., Ltd.) solid content weight ratio is 80: 1
A coating material having a concentration of 7% by weight and uniformly dispersed in a composition of 9.7: 0.3 was applied, and the coating layer was dried at 120 ° C. for 1 minute to form a drip-proof layer having a thickness of 0.8 μm. Table 1 shows the characteristics of the fluororesin film. An agricultural house was coated with the fluororesin film thus obtained. The agricultural house had good drip-proof properties and excellent durability.

Comparative Example 1 "Aflon" COP-C55A as ETFE pellets
X (manufactured by Asahi Glass Co., Ltd.) is melt-extruded in the same manner as in Example 1, and the solidified product is cooled and solidified on the cooling drum at a temperature of 150 ° C. without using the static electricity application method and without hot air treatment. An unstretched film having a size of 25 μm was obtained. The properties of the obtained film are as shown in Table 1, and it is understood that satisfactory properties cannot be obtained.

Comparative Example 2 A drip-proof layer was formed on the non-drum surface of the fluororesin film obtained in Comparative Example 1 in the same manner as in Example 3, and then an agricultural house was coated in the same manner as in Example 3. The agricultural house had uneven drip resistance and its durability was not satisfactory.

[0036]

[Table 1]

[0037]

In the fluororesin film of the present invention, since the surfaces having different surface morphologies are formed on the fluororesin film, the following excellent effects can be obtained.

First, the fluororesin film of the present invention has antifouling properties and easy adhesion, and is excellent in its durability.

Further, the agricultural house coated with the fluororesin film of the present invention has an excellent drip-proof property, and since its effect can be sustained, it does not prevent the transmission of incident light.

Since the fluororesin film of the present invention has the above-mentioned excellent properties, it is used for various optical, graphic and various substrates (plastic, glass, metal, wood,
It can be applied to a wide range such as overlays of paper, cloth, inorganic materials, etc., marking films, labels, antifouling sheets, tents, outdoor spreading materials (agricultural houses, etc.).

Claims (7)

[Claims] 1. A film containing a fluororesin as a main component, wherein the surface average roughness (Ra ₁ ) of one surface (A surface) and the surface average roughness (Ra surface) of the other surface (B surface) of the film ( Ra
₂ ) and a relationship of Ra ₁ > Ra ₂ with the fluororesin film. 2. The fluororesin film according to claim _1, wherein Ra ₁ -Ra ₂ is 0.002 μm or more. 3. The number P of protrusions having a height A on the surface of 20 to 200 mμ.
₁ and the number of protrusions P ₂ having a height of 20 to 200 mμ on the B side are P ₁
The fluororesin film according to claim 1 or 2, wherein the relationship is —P ₂ ≧ 5. 4. The fluororesin film according to any one of claims 1 to 3, wherein the fluororesin contains substantially no particles. 5. The fluororesin film according to any one of claims 1 to 4, wherein a drip-proof layer is provided on one surface (A surface) of the film. 6. The fluororesin film is ethylene-4
The fluororesin film according to any one of claims 1 to 5, comprising a composition containing a fluoroethylene copolymer resin as a main component. 7. An agricultural house characterized by comprising the fluororesin film according to any one of claims 1 to 6.