JPH04248930A - Agricultural polyethylene terephthalate film - Google Patents

Abstract

PURPOSE:To obtain an agricultural polyethylene terephthalate film not causing whitening and peeling of coating film even under a severe condition, having excellent mechanical strength and weather resistance and standing outdoor stretching. CONSTITUTION:A coating film of a composition comprising three components of a copolymer of an acrylic monomer and a perfluoroalkyl group-containing acrylic monomer, an acrylic polymer not substantially containing fluorine and a vinylidene fluoride-based resin as main components is formed on one side of a polyethylene terephthalate film orientated in 3.5 times in the biaxial directions, respectively to give an agricultural polyethylene terephthalate film.

Description

[Detailed description of the invention]

The present invention relates to an agricultural polyethylene terephthalate film that has excellent mechanical strength and excellent weather resistance (light resistance) and can withstand long-term outdoor expansion.

0002

[Prior Art] In general, polyethylene terephthalate film exhibits high crystallinity, high melting point, heat resistance and chemical resistance, and also exhibits excellent mechanical properties such as strength and elastic modulus. Are known. For this reason,
Polyethylene terephthalate film is widely used for magnetic tape, photography, electricity, metallization, packaging, agriculture, etc. However, this film has the property of absorbing ultraviolet rays, especially at 320 nm.
It has the property of strongly absorbing the following ultraviolet rays, and has the disadvantage that when this film is extended outdoors for a long period of time, its mechanical properties deteriorate significantly.

[0003] As a method for eliminating the above drawbacks, the following method has been proposed in which the surface of agricultural polyethylene terephthalate film is coated with a specific resin or paint. (i) A method of tightly bonding an ultraviolet absorber to the film surface (Japanese Patent Publication No. 46-24160) (ii) A method of forming an acrylic resin film containing an ultraviolet absorber (Japanese Utility Model Publication No. 1983-24160) (37729) (iii) Method of forming a specific acrylic resin film containing an ultraviolet absorber (Japanese Patent Laid-Open No. 60-178)
(No. 049 Publication) However, in (i), it is difficult to firmly bond the UV absorber to the film surface at a uniform concentration, and it is difficult to impart weather resistance sufficient to withstand long-term outdoor expansion and outdoor exposure. In (ii), it has excellent weather resistance, and even if exposed outdoors for a long period of time, the decrease in mechanical strength, transparency, etc. is small, but the elasticity and impact resistance of the film are If the film is stretched in a greenhouse or tunnel, the film may be bent or bent depending on the stretching method, the structure of the greenhouse or tunnel, the location and direction in which it is installed, and the weather conditions at the time of stretching. When the film is exposed to wind, cracks occur in the film, causing apparent whitening of the film, and the film peels off, making it unsatisfactory for practical use.

[0004] Although (iii) has been proposed as an improvement on these, it has not been sufficient to provide weather resistance sufficient to withstand long-term outdoor expansion and outdoor exposure.

[0005]

[Problems to be Solved by the Invention] In view of this situation, the present inventors have developed a film that does not cause whitening or peeling of the film even under severe conditions during spreading, and has excellent mechanical strength and As a result of intensive studies to provide an agricultural polyethylene terephthalate film that has weather resistance (light resistance) and can withstand long-term outdoor expansion, the present invention has been completed.

[0006]

[Means for Solving the Problems] The gist of the present invention is to provide an agricultural film with a thickness of 0.01 to 0.3 mm that is stretched 2.0 to 5.0 times in two axial directions, respectively. In polyethylene terephthalate film, on one side,
A fluorine-containing acrylic polymer [A] consisting of a copolymer of an acrylic monomer and an acrylic monomer containing a perfluoroalkyl group, an acrylic polymer substantially free of fluorine [B], and a fluorinated acrylic polymer [A] The present invention relates to an agricultural polyethylene terephthalate film formed by exposing a composition mainly containing three components of vinylidene resin [C].

The present invention will be explained in detail below. 1. Polyethylene terephthalate film Polyethylene terephthalate refers not only to non-copolymerized polyethylene terephthalate homopolymer, but also to copolymerized polyethylene terephthalate in which 85% or more of the repeating units are polyethylene terephthalate units, with the remainder being other components. and polyethylene terephthalate 8
5% by weight or more, and the remaining 15% by weight or less is another polymer. Other polymers that can be blended include polyamides, polyolefins, and other types of polyesters. This polyethylene terephthalate may be blended with a lubricant, a colorant, a stabilizer, an antioxidant, an ultraviolet absorber, etc., if necessary.

The agricultural polyethylene terephthalate film according to the present invention is biaxially stretched by 2.0 to 5.0 times. The method for producing a biaxially stretched film is not particularly limited, and for example, a known method of sequentially or simultaneously stretching the film in the vertical and horizontal directions may be employed. Moreover, if the stretching ratio is less than 2.0 times, the strength of the product will not be sufficient, which is undesirable, and if it exceeds 5.0 times, the strength of the product will be sufficient, but
This is not preferable because it makes manufacturing work difficult. The stretching ratio is particularly preferably in the range of 2.5 to 4.0 times in both biaxial directions. The thickness of the film according to the present invention is 0.01 to 0.
．． A 3mm one is good. If the thickness is less than 0.01 mm, the strength of the product will not be sufficient, which is not preferable, and if it is more than 0.3 mm, the film will become hard and difficult to handle, which is not preferable.

[0009]2. Fluorine-containing acrylic polymer [A] 2-
1. Acrylic Monomer Acrylic monomer refers to alkyl esters of acrylic acid or methacrylic acid. Specifically, the alkyl esters of acrylic acid or methacrylic acid include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, and n-propyl acrylate.
-butyl acrylate, iso-butyl acrylate,
C1-C22 alkyl esters of acrylic acid such as cyclohexyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, dodecyl acrylate, tridecyl acrylate, stearyl acrylate, etc.: methyl methacrylate, ethyl methacrylate,
n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, cyclohexyl methacrylate, 2-
Examples include C1 to C22 alkyl esters of methacrylic acid such as ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, and stearyl methacrylate.

[0010] Each of the above acrylic monomers is
Alternatively, it can be used as a mixture. Further, these acrylic monomers may be used together with other copolymerizable monomers. Examples of such other monomers include α,β-unsaturated carboxylic acid compounds containing one or more carboxyl groups in the molecule, such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid. , aconitic acid, crotonic acid, etc. For example, styrene, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, acrylamide, methacrylamide, n-butoxyacrylamide, n-butoxymethacrylamide, etc. can also be used.

2-2. Perfluoroalkyl group-containing acrylic monomer The perfluoroalkyl group-containing acrylic monomer is an ester of acrylic acid or methacrylic acid having a perfluoroalkyl group, specifically, 2, 2,
2-trifluoroethyl acrylate, 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl acrylate, 2,2,3,3-
Tetrafluoropropyl methacrylate, 2,2,3,
3,3-pentafluoropropyl acrylate, 2,2
, 3,3,3-pentafluoropropyl methacrylate, 1-trifluoromethyl-2,2,2-trifluoroethyl acrylate, 1-trifluoromethyl-2,2
, 2-trifluoroethyl methacrylate, 2,2,3
, 3,4,4,5,5-octafluoropentyl acrylate, 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 2,2,3,3,4,4
-hexafluorobutyl acrylate, 2,2,3,3
, 4,4-hexafluorobutyl methacrylate, 2-
Examples include perfluorooctyl ethyl acrylate, 2-perfluorooctyl methacrylate, 2-perfluorononylethyl acrylate, 2-perfluorononylethyl methacrylate. Among these, those in which the number of fluorine atoms in the perfluoro group is 5 or more are particularly preferred. These may be used alone or in combination of two or more.

2-3. The copolymerization ratio of the blended acrylic monomer and the perfluoroalkyl group-containing acrylic monomer is generally preferably in the range of 20 to 99% by weight. If the amount of acrylic monomer is less than this range, the adhesion of the formed film to the substrate will not be sufficient, and if it is more than this range, it will not function as a fluorine-containing acrylic polymer. A predetermined amount of an acrylic monomer and a pearl fluoroalkyl group-containing acrylic monomer are mixed together and charged into a polymerization tank together with an organic solvent. A polymerization initiator and, if necessary, a molecular weight regulator are added, and the mixture is heated with stirring. , polymerize. For polymerization, generally known methods such as suspension polymerization and solution polymerization are employed. In this case, examples of polymerization initiators that can be used include radical-generating catalysts such as α,α-azobisisobutyronitrile, benzoyl peroxide, and cumene hydroperoxide, and examples of molecular weight regulators include butyl mercaptan and n- Examples include dodecyl mercaptan, tert-dodecyl mercaptan, and β-mercaptoethanol.

[0013] Examples of organic solvents used in polymerization include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, tert-amyl alcohol, and n-hexyl alcohol. , alcohols such as cyclohexanol; aromatic hydrocarbons such as benzene, toluene, and xylene; acetate esters such as ethyl acetate and butyl acetate; acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl isobutyl ketone, diethyl ketone, 2-hexanone, 3
- Ketones such as hexanone, di-n-propyl ketone, diisopropyl ketone, di-n-amyl ketone, and cyclohexanone; tetrahydrofuran, etc.;
A species or a mixture of two or more kinds can be used.

3. Acrylic polymer [B] The acrylic polymer [B] that does not substantially contain fluorine is a polymer mainly composed of alkyl esters of acrylic acid or methacrylic acid described in 2-1, and the same Obtained by polymerization method.

4. Vinylidene fluoride resin [C] Vinylidene fluoride resin [C] is a homopolymer of vinylidene fluoride, or a copolymer of vinylidene fluoride and other fluorinated unsaturated monomers and/or fluorine-free. Copolymers with possible monomers and polymers obtained by partially modifying or modifying these polymers are also included. These vinylidene fluoride resins can be used alone or in combination of two or more. It may also be used in combination with other fluorine-containing resins, such as tetrafluoroethylene, chlorotrifluoroethylene, fluoroethylene, etc.

5. The blending amounts of the coating fluorine-containing acrylic polymer [A], the acrylic polymer substantially free of fluorine [B], and the vinylidene fluoride resin [C] are as follows: [A] 3 to 50 parts by weight, [B] ]2
~40 parts by weight, [C] 10 to 95 parts by weight. resin〔
If the ratio of polymer [A] to C] is too small, the formed film will not have sufficient transparency. On the other hand, if the ratio of the polymer [B] to the resin [C] is too small, the adhesion of the formed film to the substrate surface will be poor and the film will easily peel off, which is undesirable. On the other hand, polymer [A] or polymer [
If the proportion of B] is too high, the effect on the migration prevention properties of plasticizers, etc., stain resistance, and water resistance of the formed film will not be sufficient, which is not preferable.

[0017] In addition to these components, this coating composition may contain an ultraviolet absorber, which can be used by dispersing and/or dissolving it in an organic solvent. Types of ultraviolet absorbers include conventionally known ultraviolet absorbers such as salicylic acid compounds, cyanoacrylate compounds, benzophenone compounds, and benzotriazole compounds. Among these, ethyl-2-cyano-3 among cyanoacrylate compounds was evaluated from the viewpoint of solubility in acrylic resins, weather resistance when applied to polyethylene terephthalate film for agricultural use, etc. , 3-diphenylacrylate, 2,4-dihydroxybenzophenone among benzophenone compounds, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4 , 4'-dimethoxybenzophenone is preferred, and among benzotriazole compounds, 2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole is particularly preferred. These may be used alone or in combination of two or more. The blending amount is preferably in the range of 1 to 30% by weight based on the resin solid content of the coating composition.

Examples of organic solvents include aliphatic hydrocarbons such as heptane and cyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; alcohols such as methanol, ethanol, isopropyl alcohol, and polyoxyethylene glycol; and halogenated carbons. Chloroform, tetrachlorinated hydrocarbons, chlorobenzene, etc. as hydrogen; acetone, methyl ethyl ketone, etc. as ketones.
Methyl isobutyl ketone, etc.; esters such as methyl acetate, allyl acetate, ethyl stearate, etc.;
Examples of amines include trimethylamine, diphenylamine, hexamethylene diamine, etc.; and dimethylformamide, dimethylacetamide, dioxane, diethyl ether, diethylene dithioglycol, diacetone alcohol, benzonitrile, dimethyl sulfoxide, etc., which may be used alone or in combination. The above can be used in combination.

Various known methods can be applied to form a film on the surface of a polyethylene terephthalate film by applying the above-mentioned film composition, depending on the shape of the molded product. For example, when forming a film in a solution state, coating methods such as doctor blade coating method, gravure roll coating method, air knife coating method, reverse roll coating method, dip coating method, curtain roll coating method, spray coating method, rod coating method, etc. method is used.

In the present invention, the thickness of the coating formed on the surface of the base film is 1/10 of the thickness of the base film.
It is preferable that it is below. If the thickness of the coating is more than 1/10 of the base film, there is a difference in flexibility between the base film and the coating, so phenomena such as peeling of the coating from the base film are likely to occur, and cracks may occur in the coating. This is undesirable because a phenomenon occurs in which the strength of the base film decreases. In addition, before applying the above film composition, the surface of the polyethylene terephthalate film should be cleaned with alcohol or water, subjected to plasma discharge treatment or corona discharge treatment, or undercoated with other paint or primer. It may be processed.

[0021] When the agricultural polyethylene terephthalate film according to the present invention is actually used for agricultural purposes, the side on which the film is provided is placed on the outside of a greenhouse or tunnel.

[0022]

[Effects of the Invention] The agricultural polyethylene terephthalate film according to the present invention has the following properties when extended outdoors for a long time:
The degree of discoloration and deterioration of physical properties is small, and the strong adhesion between the base material and the coating makes it difficult for the coating to peel off.The coating is non-sticky and has little adhesion, making it transparent and transparent. It is suitable for agricultural applications because it maintains the rate for a long period of time.

[0023]

EXAMPLES The present invention will be explained in detail below based on examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Examples 1 to 5 Comparative Examples 1 to 5 (1) Base polyethylene terephthalate film length and width each 3
．． Stretched 5 times, density 1.392g/cm2, thickness 125μ.

(2) Adjustment of fluorine-containing acrylic polymer [A] Into a reactor equipped with a thermometer, a stirrer, a reflux condenser, and a nozzle for adding raw materials, 70 parts by weight of methyl ethyl ketone, 30 parts by weight of toluene, and benzoyl peroxide were added. 1.0 parts by weight and 100 parts by weight of a mixture of each monomer shown in Table 1 were charged,
While stirring in a nitrogen gas stream, the reaction was continued at 80°C for 3 hours, and 0.5 parts by weight of benzoyl peroxide was added thereto for about 3 hours.
Resins a and b, which are fluorine-containing acrylic polymers, were obtained by continuing at the same temperature.

(3) Preparation of acrylic polymer [B] (2
), 70 parts by weight of methyl ethyl ketone,
30 parts by weight of toluene, 1.0 parts by weight of benzoyl peroxide, and 100 parts by weight of the mixture of each monomer shown in Table 1 were charged, and while stirring in a nitrogen gas stream, benzoyl peroxide was further added at 70°C for 3 hours. After adding 0.5 parts by weight, the reaction was continued at the same temperature for about 3 hours to form resins c and d, which are acrylic polymers.
I got it.

(4) Formation of a coating Fluorine-containing acrylic polymer of the type and amount shown in Table 2 [
A], an acrylic polymer [B], and a commercially available vinylidene fluoride resin [C] are blended, and the solid content is 20%.
Methyl ethyl ketone was added in an amount of % by weight to obtain a coating composition. The above film composition was continuously coated on one side of the base film by a roll coating method, and then dried in a drying oven for 100 minutes.
C. for 1 minute to volatilize the solvent and at the same time heat treatment was performed, and each film was wound up. The amount of coating on each film obtained was approximately 3 g/m2.

(5) Evaluation of film The performance of the film was evaluated using the following method, and the results are shown in Table 3.

(i) Initial direct light transmittance at a wavelength of 555 nm Measured using a spectrophotometer (manufactured by Hitachi, Ltd., Model EPS-2U).

(ii) Adhesive strength of the film Cellophane tape (manufactured by Nichiban) was applied to the polyethylene terephthalate film.
Judgment was made by observing with the naked eye the changes in the film after pasting the cellophane tape and peeling off the cellophane tape. The criteria for judgment were as follows. ◎...The coating did not peel off at all and remained completely. ○...2/3 or more of the coating remained without being peeled off. △...2/3 or more of the coating was peeled off. ×...The film was completely peeled off.

(iii) Outdoor expansion test Ten types of films were installed in a roof-type house (frontage 3 m, depth 5 m, ridge height 1.5 m) in a test field in Isshi District, Mie Prefecture.
, a roof slope of 30 degrees) was coated with the coated surface facing the outside of the greenhouse, and an expansion test was conducted for 3 years from March 1980 to February 1990. Regarding the stretched film,
The direct light transmittance at a wavelength of 555 nm and the elongation retention of the film were evaluated, and the results are shown in Table 3. The elongation retention rate of the film means a value calculated using the following formula.

(Elongation of the film after stretching) ÷ (Elongation of the film before stretching) x 100 (%)

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

Claims (1)

[Claims] Claim 1: An agricultural polyethylene terephthalate film with a thickness of 0.01 to 0.3 mm stretched 2.0 to 5.0 times in each biaxial direction, on one side of which:
A fluorine-containing acrylic polymer [A] consisting of a copolymer of an acrylic monomer and an acrylic monomer containing a perfluoroalkyl group, an acrylic polymer substantially free of fluorine [B], and a fluorinated acrylic polymer [A] An agricultural polyethylene terephthalate film formed with a coating of a composition containing three main components of vinylidene resin [C].