JPH07705B2 - Method for producing coated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a method for producing a transparent coating film which is excellent in weather resistance, scratch resistance and the like and which is particularly suitable for agriculture.

<Prior art> In recent years, tunnel cultivation and greenhouse cultivation of plants have been widely adopted, and plastic films are used for keeping plants warm and protecting them from wind and rain.

Polyethylene film and polyvinyl chloride film were mainly used as the plastic film.

However, polyethylene films have insufficient transparency and heat resistance, and polyvinyl chloride films have large changes in physical properties due to temperature changes, for example, they become soft in the summer and have self-adhesiveness, and hard in the winter. The plasticizer gradually disappears and becomes brittle when used for a long period of time.

So, recently, for electrical insulation materials, tapes, for drawing and photography,
Polyester films, which are widely used in the fields of labels and packaging, have been receiving attention as agricultural plastic films.

<Problems to be solved by the invention> By the way, the polyester film has excellent tensile strength,
Although it has impact resistance, tear strength, heat / cold resistance, water resistance, etc., and has a large elongation rate and good transparency, it has the same weather resistance and scratch resistance as the conventional plastic film. Since it is inferior in comparison, it has not been widely adopted for agricultural use, although it has the above various excellent performances.

In view of such a current situation, the present invention has led to the present invention as a result of earnest studies in order to improve the weather resistance, scratch resistance and the like while making the best use of the characteristics of the polyester film.

<Means for Solving Problems> That is, the present invention is a transparent polyester film surface,
Characterized by applying a room temperature-curable clear coating composed of a fluorine-containing copolymer having a hydroxyl group and polyisocyanate and drying it to form a clear fluororesin coating film, and then forming a clear hard coat coating film on the coating film. The present invention relates to a method for producing a coated film.

In the present invention, for both layers of the polyester film and the clear hard code coating film, a clear fluororesin coating film having good adhesion and excellent weather resistance is applied to the polyester film surface, and further on the clear fluororesin coating film surface. Since it has a clear hard-coded coating, the resulting coating film is greatly improved in weather resistance and scratch resistance in addition to the excellent properties of the polyester film, so it is always exposed to sunlight, wind and rain. It is suitable as a plastic film used in the fields of agriculture and gardening.

In the present invention, the polyester film is polyethylene terephthalate (PE) obtained by polycondensation of ethylene glycol and terephthalic acid (or its ester).
T) Film, various polyester films in which a part of terephthalic acid is replaced with isophthalic acid or the type of polyhydric alcohol is changed, and generally commercially available polyester films can be used. The thickness of the polyester film is not particularly limited, but when used for agriculture,
Usually, a size of 25 to 300 μ is suitable.

Next, the room temperature curable clear coating used in the present invention has good adhesion to both layers of the polyester film and a clear hard coat coating film described later, and in order to improve the poor weather resistance of the polyester film, A clear coating containing a fluorine-containing copolymer and polyisocyanate as main components is used.

The room temperature-curable clear coating material used in the present invention, which is generally known to have poor adhesion to a coating material, has excellent adhesion to the polyester film. The reason is that the van der Waals force is a hydrogen bond, the reaction between isocyanate groups and hydroxyl groups on the surface of the polyester film, and the organic solvent in the clear paint causes the polyester film to swell, resulting in the paint resin entering the polyester film interface. It is considered that the adhesion is improved.

As the fluorine-containing copolymer having a hydroxyl group (hereinafter, referred to as “fluorine-containing copolymer” for convenience), a fluorine-containing copolymer having a hydroxyl group and containing fluoroolefin and cyclohexyl vinyl ether is desirable. In particular, JP-A-57
Since the copolymer described in JP-A-32107 has not only weather resistance but extremely low moisture permeability and can be either room temperature cured or low temperature bake cured, it can be suitably used. That is, the copolymer preferably used in the present invention, fluoroolefin, cyclohexyl vinyl ether, alkyl vinyl ether and hydroxyalkyl vinyl ether as an essential constituent component, respectively.
40-60 mol%, 5-45 mol%, 5-45 mol% and 3-
15 mol% ratio, preferably 45-55 mol%, 10 respectively
It is contained in a proportion of -30 mol%, 10-35 mol% and 5-13 mol%, and a weight average molecular weight of about 1-100,000 is suitable.

If the content of the fluoroolefin is too low, the weather resistance is lowered, and if it is too high, the production is difficult. Further, if the content of cyclohexyl vinyl ether is too low, the hardness when formed into a coating film decreases, and if the content of alkyl vinyl ether is too low, the flexibility decreases.

Also, if the hydroxyalkyl vinyl ether content is too low, the mechanical strength and adhesion of the coating film will decrease, and if it is too high, the solubility of the copolymer will change, and it will not be possible to use it in specific solvents such as alcohols. Since it only dissolves, the applicability as a solvent-based paint base is limited, which is not preferable.

In the fluorine-containing copolymer, the fluoroolefin is preferably a perhaloolefin, particularly chlorotrifluoroethylene or tetrafluoroethylene.

Further, as the alkyl vinyl ether, one containing a linear or branched alkyl group having 2 to 8 carbon atoms, particularly one having 2 to 4 carbon atoms in the alkyl group is preferable.

Further, the above-mentioned fluorine-containing copolymer can contain other comonomer other than the above-mentioned four essential constituent components within a range not exceeding 30 mol%. Such comonomers include olefins such as ethylene, propylene and isobutylene; haloolefins such as vinyl chloride and vinylidene chloride; unsaturated carboxylic acid etching compounds such as methyl methacrylate; vinyl acetate, n-vinyl acetate and the like. Vinyl carboxylates; unsaturated carboxylic acids such as fumaric acid, maleic acid, acrylic acid and methacrylic acid.

The fluorine-containing copolymer is produced by causing a copolymerization reaction by causing a polymerization initiation source such as a polymerization agent or ionizing radiation to act on a monomer mixture in a predetermined ratio in the presence or absence of a polymerization medium. To be done.

As such a fluorine-containing copolymer, Lumiflon LF10
0, Lumiflon LF200, Lumiflon LF210, Lumiflon LF3
00, Lumiflon LF400, Lumiflon LF510, Lumiflon LF
700 (all manufactured by Asahi Glass Co., Ltd.) is commercially available.

Polyisocyanate is a compound having two or more isocyanate groups in one molecule and is used as a curing agent.

Examples of the polyisocyanates include hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), hydrogenated diphenylene diisocyanate, hydrogenated xylylene diisocyanate, and the like, or aliphatic or alicyclic diisocyanates. Typical examples thereof include reaction products of these burettes, doubles, triples or excess of these isocyanate compounds and low molecular weight polyols such as ethylene glycol, glycerin, trimethylolpropane and pentaerythritol. .

The room temperature curable clear coating used in the present invention is a fluorine-containing copolymer and polyisocyanate as described above, the equivalent ratio of the isocyanate group in the polyisocyanate to the hydroxyl group in the fluorine-containing copolymer (NCO / OH). Is [(0.8
To 1.6) / 1] as a main component, and mixed with xylene, toluene, ethyl acetate, butyl acetate, ethyl ethyl ketone, methyl isobutyl ketone, n-heptane, n-hexane, ethylene acetate. Various organic solvents commonly used for coating materials such as glycol monoether; benzophenone-based compounds such as 2-hydroxy-4-methoxybenzophenone, benzo such as 2- (2'-hydroxy-4'-normaloctoxyphenyl) benzotriazole It is composed of various ultraviolet absorbers such as triazole and salicylate compounds; other light stabilizers such as hindered amine compounds and hindered phenol compounds, and various additives such as oxidative spinning agents, if necessary. The UV absorber is preferably added in an amount of 0.5 to 5% by weight in the solid content of the room temperature curable clear coating material.

Next, the clear hard coat coating used in the present invention imparts a high surface hardness to the coating film, improves scratch resistance, and protects the coating film from scratches due to collision of sand or the like during handling of the coating film or after installation. To prevent
It is applied on the clear fluororesin coating film.

In the present invention, the clear hard code coating film has a pencil hardness (based on JIS K5400 6.14) of 4H or more.
As the paint forming the clear hard coat coating film (hereinafter referred to as “hard code paint” for convenience sake), conventional code hard paints can be used without particular limitation as long as they have the above hardness, but in the present invention, The UV-curable coating composition containing acrylate and / or methacrylate monomer having two or more ethylenically unsaturated groups in one molecule as a main component has high hardness and further has appropriate flexibility and weather resistance. It can be used suitably.

That is, the UV-curable coating composition comprises 30 to 100% by weight of an acrylate and / or a methacrylate having two or more ethylenically unsaturated groups in one molecule (hereinafter, both are referred to as “(meth) acrylate” for convenience). Other monomer 7
0.1 to 10 parts by weight of a photosensitizer with respect to 100 parts by weight of a monomer mixture consisting of 0 to 0% by weight, and if necessary, an organic solvent,
It is composed of various additives such as an ultraviolet absorber, an antioxidant and a light stabilizer.

Examples of the (meth) acrylate monomer having two or more ethylenically unsaturated groups in one molecule include ethylene glycol di (meth) acrylate, 1,3-propylene glycol di (meth) acrylate and 1,4- Butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) ) Acrylate, trimethylolethane tri (meth) acrylate,
Typical examples include pentaglycerol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate and the like.

Other monomers include methyl (meth) acrylate,
Ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ethoxyethyl (meth) acrylate, 2-butoxydiethyl (meth) acrylate, (meth) acrylic acid, (meth) acrylamide, styrene, etc. As a representative one. In the present invention, a mixture obtained by appropriately selecting and mixing these monomers so that the coating film hardness is 4H or more may be used.

Representative examples of the photosensitizer include benzoyl, benzoin ethyl ether, acetoin, benzophenone, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzoyl peroxide, and ditertiary butyl peroxide.

Next, a method for producing the coated film of the present invention will be described.

First, after subjecting the surface of the polyester film to surface treatment such as degreasing, if necessary, the room temperature curable clear coating is applied.
The polyester surface is coated by means such as spray coating, roller coating, flow coating, rotary coating, and dip coating, and dried at room temperature or forcedly dried at a temperature of 130 ° C or lower.

A dry film thickness of about 5 to 60 μ is suitable. If the film thickness is smaller than the above range, it does not contribute much to the improvement of the weather resistance of the polyester film, while if it is too thick, cracks and the like are likely to occur due to the difference in elongation rate from the polyester film.

Then, a clear hard coat coating material is applied onto the clear fluororesin coating film thus obtained by the same means as described above, and dried at room temperature or forcedly dried.

When the ultraviolet-curable coating material is used, it is cross-linked and cured by an ordinary method, that is, ultraviolet rays emitted from a light source such as a xenon lamp, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp or an ultra-high pressure mercury lamp.

The suitable dry film thickness of the clear hard coat coating film is about 1 to 30 μm. If the film thickness is smaller than the above range, it does not contribute much to the scratch resistance of the polyester film, and if it is too thick, cracks and the like are likely to occur. In particular, the coated film is often wound, cut, bent, etc., so 2-11
About μ is desirable.

<Effect of the Invention> The present invention has a tensile strength of a polyester film,
While taking advantage of excellent properties such as tear strength, heat / cold resistance, and water resistance, it also has the disadvantages of poor weather resistance, scratch resistance, etc. This is improved by applying a specific clear fluororesin coating film and a clear hard coat coating film having excellent properties.

Therefore it is used outdoors. For example, a polyester film has not been used as an agricultural cover film due to the above-mentioned drawbacks, but the coated polyester film obtained by the present invention solves the above-mentioned drawbacks and can be suitably applied as an agricultural film. It can be suitably applied to various uses such as a lighting equipment cover.

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

In addition, "part" and "%" are shown on a weight basis.

<Preparation of Fluorine-Containing Copolymer Solution> (i) Preparation of Fluorine-Containing Copolymer Solution (A) Tetrafluoroethylene 50 mol%, cyclohexyl vinyl ether 25 mol%, ethyl vinyl ether 12 mol%,
A monomer consisting of 13 mol% of hydroxybutyl vinyl ether was polymerized according to the method described in JP-A-57-34107 to prepare a 50% xylene solution of a fluorine-containing copolymer (Tg 45 ° C, hydroxyl value 68). . [Hereinafter referred to as fluorinated copolymer solution (a)] (ii) Preparation of fluorinated copolymer solution (a) Chlorotrifluoroethylene 52 mol%, cyclohexyl vinyl ether 17 mol%, ethyl vinyl ether 22 mol%, hydroxybutyl ether 9 Polymerizing a monomer consisting of mol% according to the method described in JP-A-57-34107,
A 50% xylene solution of a fluorinated copolymer (Tg 35 ° C, hydroxyl value 40) was prepared. [Hereinafter, fluorinated copolymer solution (a)
Example 1 A 125 μ-thick polyester film [“ES100” (trade name, manufactured by Toyobo Co., Ltd.)] was degreased with gauze containing xylene, and then the fluorocopolymer solution (a) 100
Part, 2-hydroxy-4-methoxybenzophenone 1
Room temperature curing, which is a mixture of 12 parts of a main component consisting of 10 parts of xylene and 12 parts of a trimer of hexamethylene diisocyanate [“Coronate ET” (trade name of Nippon Polyurethane Co.)] and a curing agent consisting of 12 parts of butyl acetate. Type clear paint is applied by air spray, dried at 100 ℃ for 10 minutes, and the film thickness is 3
A 0 μ clear fluororesin coating film was formed.

Then pentaerythritol tetraacrylate (PET
A) 30 parts, trimethyl propane triacrylate (TMPT
A) 40 parts, 1,6-hexanediol diacrylate (1,6H
DDA) 30 parts, benzoin isobutyl ether 1 part, 2-
A UV-curable coating consisting of 1 part of hydroxy-4-methoxybenzophenone, 50 parts of toluene and 70 parts of butyl acetate (pencil hardness 7H based on JIS K 5400 6.14 of a single coating after UV curing) was clear by a roll coater. The fluororesin coating film was applied again, dried at 80 ° C. for 5 minutes with hot air, and then irradiated with ultraviolet rays from a medium-high pressure mercury lamp to form a clear hard coat coating film having a thickness of 3 μm to prepare a coating film.

The performance of the obtained coated film was as shown in Table 2.

Examples 2 to 4 A coating film was prepared in the same manner as in Example 1 using the room temperature curable clear coating material and the ultraviolet curable coating material shown in Table 1. The performance of the obtained coated film was as shown in Table 2.

Comparative Example 1 In Example 1, the clear fluororesin coating film was not applied,
A coating film was prepared in the same manner as in Example 1 except that the clear hard coat coating film was directly formed. The performance of the obtained coated film was as shown in Table 2.

Comparative Example 2 A coated film was prepared in the same manner as in Example 1 except that the clear hard resin coating film was not applied in Example 1 and only the clear fluororesin coating film was formed. The performance of the obtained coated film was as shown in Table 2.

Reference Examples 1 to 3 The performance of the 125 μm-thick polyester film (Reference Example 1), the commercially available soft vinyl chloride resin film (Reference Example 2), and the commercially available high-pressure polyethylene film (Reference Example 3) are not applied. The results are shown in Table 2.

As is clear from Table 2, the coating film obtained by the method of the present invention had excellent properties such as weather resistance, adhesion and scratch resistance.

On the other hand, in Comparative Example 1 in which the clear fluororesin coating film was not applied, the weather resistance was poor, and in Comparative Example 2 in which the clear hard coat film was not applied, the scratch resistance was poor.

Claims (3)

[Claims] 1. A polyester film surface is coated with a room temperature-curable clear paint comprising a hydroxyl group-containing fluorocopolymer and polyisocyanate and dried to form a clear fluororesin coating film, which is then formed on the coating film. A method for producing a coated film, which comprises forming a clear hard coat coating film. 2. The clear hard coat coating film is a cured coating film of an ultraviolet curable coating composition containing as a main component an acrylate and / or methacrylate monomer having two or more ethylenically unsaturated groups in one molecule. The method for producing a coated film according to claim (1), characterized in that: 3. The method for producing a coated film according to claim 1, wherein the coated film is for agricultural use.