JPH0455616B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a polyethylene terephthalate film for agricultural use. More specifically, the present invention relates to an agricultural polyethylene terephthalate film having excellent mechanical strength, excellent weather (light) resistance, and excellent antifogging properties. (Prior art and its problems) In general, polyethylene terephthalate film exhibits high crystallinity, high melting point, excellent heat resistance and chemical resistance, and also has good mechanical properties such as strength and elastic modulus. It is known to exhibit excellent properties. For this reason, polyethylene terephthalate film is used for magnetic tape, photography,
It is widely used for electrical purposes, metallization, packaging, agriculture, etc. However, since the surface of polyethylene terephthalate film is hydrophobic, when it is used as a covering material for an agricultural greenhouse (greenhouse), depending on conditions such as temperature and humidity inside the greenhouse, the inside surface of the film may cloudiness occurs. This cloudiness reduces the amount of light that passes through the film, slowing down plant growth, and causing water droplets to fall on cultivated plants, damaging young buds and causing diseases. This causes various inconveniences, such as making workers inside the house feel uncomfortable. It is known that in order to eliminate such inconveniences, it is sufficient to impart antifogging properties to the film surface. To impart antifogging properties to the film surface, there are methods such as incorporating a hydrophilic substance such as a surfactant into the film, or coating the film surface with a hydrophilic substance or a water-soluble polymer substance. It has been known. However, the former method is less effective with hard resins such as polyethylene terephthalate, and attempts have been made to provide antifogging properties using the latter method. For example, Japanese Patent Publication No. 46-13252, Japanese Patent Publication No. 49-1983
No. 70885 and JP-A-50-71770 disclose a method of applying a water-soluble hydrophilic substance such as polyvinyl alcohol, and Japanese Patent Publication No. 50-6437 and JP-A-53
JP-A-37075 proposes a method of applying a composition comprising a hydrophilic polymer containing hydroxyalkyl acrylate as a main component, a surfactant, and the like. However, these hydrophilic substances are susceptible to hydrolysis and therefore have poor water resistance, and also have poor adhesion to hydrophobic polyethylene terephthalate film, so especially under humid conditions, coatings derived from these hydrophilic substances are It easily peels off from the film surface and cannot exhibit sufficient antifogging performance. In order to improve these shortcomings, for example,
No. 56-34219 proposes a method of making a hydrophilic acrylic acid ester polymer containing a hydroxyl group insoluble in water using a crosslinking agent. However, according to this method, the antifogging property itself also decreases, so it cannot be said to be a satisfactory improvement method. On the other hand, a method of applying a mixture of an inorganic aqueous sol and a surfactant has been proposed as a method for imparting hydrophilicity. For example, Japanese Patent Publication No. 50-11348 discloses a product containing surfactant as the main ingredient and a small amount of silica sol added thereto, and Japanese Patent Publication No. 49-32668 discloses
Alumina sol with surfactant added, JP-A-Sho
No. 58-29831 discloses colloidal silica with a small amount of water-soluble aluminum salt added thereto. However, since these mixtures have poor adhesion to polyethylene terephthalate, which is an organic substance, the formed coating film falls off over time, and has the disadvantage that the antifogging effect cannot be maintained over a long period of time. In order to improve the above drawbacks, for example, JP-A-51-
Publication No. 81877 describes an alumina sol containing a surfactant and a hydrophilic polymer, JP-A-57-119974.
Publication No. 187347, Japanese Patent Publication No. 187347, Japanese Patent Application Publication No. 1873-
Publication No. 15473 discloses colloidal silica with a hydrophilic polymer and a surfactant added thereto. However, since these compositions contain hydrophilic polymers such as polyvinyl alcohol and hydroxyl group-containing acrylic resins for the purpose of achieving miscibility with inorganic aqueous sols, the formed coating films tend to be inherently inferior in water resistance. There is. Therefore, if constantly exposed to humid conditions, the inorganic aqueous sol will be washed away together with the hydrophilic polymer or will have poor dispersion, and the antifogging effect will be lost in a short period of time, making it unsatisfactory for practical use. Furthermore, in order to improve the above-mentioned drawbacks, for example, JP-A No. 55-99976 and JP-A No. 55-99987 disclose prevention using an inorganic-organic composite reactant consisting of silica/hydrophilic polymer/organosilicon compound. A method of imparting haze has been proposed. However, these methods also do not have sufficient water resistance, and the antifogging performance is also not satisfactory, making it impossible to fully achieve the intended purpose. (Means for Solving the Problems) Against this background, the present inventors have developed a method that does not reduce its mechanical strength even when used for a long period of time as a house covering, etc., and has excellent weather (light) resistance. In order to provide an agricultural polyethylene terephthalate film that exhibits excellent antifogging properties and maintains excellent antifogging properties for a long period of time, the present invention was completed as a result of intensive studies. Therefore, the gist of the present invention is that (a) 60 to 100% by weight of a monomer consisting of an alkyl ester of acrylic acid or methacrylic acid or A mixed monomer of alkyl esters of acrylic acid or methacrylic acid and alkenylbenzenes and other α,β-ethylenically unsaturated monomers that can be copolymerized with 0 to 40% by weight of the above monomers. and (b) one or more types of inorganic colloidal sol. (a) of
and (b), or an antifogging agent composition containing a mixture of the above two components (a) and (b), a crosslinking agent, and/or a liquid dispersion medium. An agricultural polyethylene terephthalate film coated with The present invention will be explained in detail below. The polyethylene terephthalate referred to in the present invention includes not only non-copolymerized polyethylene terephthalate homopolymer, but also copolymerized polyethylene terephthalate in which the repeating unit of ethylene terephthalate is 85% or more and the remainder is other components, Polyethylene terephthalate is 85
% by weight or more, and the remaining 15% by weight or less includes a polymer blend of other polymers. Other polymers that can be blended include polyamides, polyolefins, and other types of polyesters. Additives such as lubricants, colorants, stabilizers, and antioxidants, which are usually added to polyethylene terephthalate, can be added to the polyethylene terephthalate, if necessary. The agricultural polyethylene terephthalate film according to the present invention may be unstretched or biaxially stretched, but from the viewpoint of film strength, biaxially stretched is preferred. In the case of biaxial stretching, it is preferable to stretch 2.0 to 5.0 times in both length and width. If the stretching ratio is less than 2.0 times, the strength of the product will not be sufficient, which is undesirable. If the stretching ratio exceeds 5.0 times, the strength of the product will be sufficient, but it will be undesirable because the manufacturing work will be difficult. . The stretching ratio is both biaxial,
Particularly preferred is a range of 2.5 to 4.0 times, respectively. The method for producing a biaxially stretched film is not particularly limited, and any conventionally known method may be used, such as sequentially or simultaneously stretching the film in the vertical and horizontal directions. The agricultural polyethylene terephthalate film according to the present invention preferably has a thickness of 0.01 to 0.3 mm. If the thickness is less than 0.01 mm, the strength of the product will not be sufficient, which is not desirable.
If it exceeds 0.3 mm, the film becomes hard and difficult to handle, which is not preferable. The agricultural polyethylene terephthalate film according to the present invention contains at least an ultraviolet absorber. Examples of the ultraviolet absorbent used here include the following. 2- which is a cyanoacrylate ultraviolet absorber
Ethylhexyl-2-cyano-3,3'-diphenyl acrylate, ethyl-2-cyano-3,3'-
Diphenyl acrylate. 2-Hydroxy-4-methoxybenzophenone, 2,4- which is a benzophenone ultraviolet absorber
Dihydroxybenzophenone, 2-hydroxy-
4-n-octoxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-benzoyl Oxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfonebenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-5-chlorobenzophenone, bis-(2-methoxy-4-
Hydroxy-5-benzoylphenyl)methane. 2- which is a benzotriazole ultraviolet absorber
(2′-hydroxyphenyl)benzotriazole,
2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5-
methylphenyl)-5-carboxylic acid butyl ester benzotriazole, 2-(2'-hydroxy-
5'-methylphenyl)-5,6-dichlorobenzotriazole, 2-(2'-hydroxy-5'-methylphenyl)-5-ethylsulfonebenzotriazole, 2-(2'-hydroxy-5'-t-butylphenyl) )-5-chlorobenzotriazole, 2
-(2'-hydroxy-5'-butylphenyl)benzotriazole, 2-(2'-hydroxy-5'-aminophenyl)benzotriazole, 2-(2'-
Hydroxy-3',5'-dimethylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-dimethylphenyl)-5-methoxybenzotriazole, 2-(2'-methyl-4' -hydroxyphenyl)benzotriazole, 2-(2'-stearyloxy-3',5'-dimethylphenyl)-5-methylbenzotriazole, 2-(2'-hydroxy-
5-Carboxylic acid phenyl)benzotriazole ethyl ester, 2-(2'-hydroxy-3'-methyl-5'-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di- t-butylphenyl)-5-chlorobenzotriazole,
2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole,
2-(2'-hydroxy-5'-methoxyphenyl)
Benzotriazole, 2-(2'-hydroxy-3',
5'-di-t-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-5'-cyclohexylphenyl)benzotriazole, 2
-(2'-hydroxy-4',5'-dimethylphenyl)
-5-Carboxylic acid benzotriazole butyl ester, 2-(2'-hydroxy-3',5'-dichlorophenyl)benzotriazole, 2-(2'-hydroxy-4',5'-dichlorophenyl)benzotriazole, 2- (2'-hydroxy-3',5'-dimethylphenyl)-5-ethylsulfonebenzotriazole, 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole, 2-(2'-hydroxy -5'-methoxyphenyl)-5-methylbenzotriazole, 2-(2'-hydroxy-5'-methylphenyl)-5-carboxylic acid ester benzotriazole, 2-(2'-acetoxy-5'-methylphenyl) Benzotriazole. Although the above-mentioned ultraviolet absorbers can be mentioned, it is particularly desirable to use benzophenone-based ultraviolet absorbers or benzotriazole-based ultraviolet absorbers. These ultraviolet absorbers can be used alone or in combination of two or more, and the amount used is 0.01 to 5 parts by weight, preferably 0.05 to 2 parts by weight, per 100 parts by weight of polyethylene terephthalate. If the amount used is too small, the desired effect of improving the anti-fog durability will not be obtained, and if it is too high, the effect of improving the anti-fog durability will not be seen as much compared to the amount used, and the UV absorber will not be able to improve the durability of the film. This is not preferable because it bleeds onto the surface and reduces the transparency of the film. In the present invention, the inclusion of an ultraviolet absorber in the polyethylene terephthalate film means that it is blended into the resin composition before film molding,
After that, it refers to a film that is formed into a film, or a film that has a UV absorber applied to its surface after forming the film, and when coating the surface of the latter base film, ultraviolet rays are added to the coating film components. Just mix an absorbent and apply it. These methods can be used alone or in combination. The hydrophobic acrylic resin that is a component of the antifogging agent composition used in the present invention has a molecular weight of 60 to 100%.
% by weight of alkyl esters of acrylic acid or methacrylic acid [hereinafter abbreviated as (meth)acrylic acid alkyl esters]. ], or a mixed monomer consisting of (meth)acrylic acid alkyl esters and alkenylbenzenes, and an α,β-ethylenically unsaturated monomer that can be copolymerized with 0 to 40% by weight of the above monomer. This is a copolymer obtained by emulsion polymerization of the following in an aqueous medium in the presence of a surfactant. Examples of the (meth)acrylic acid alkyl esters used in the present invention include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, and n-acrylate.
Butyl, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, etc. Generally, acrylic acid alkyl esters having an alkyl group having 1 to 20 carbon atoms and/or methacrylic acid alkyl esters having an alkyl group having 1 to 20 carbon atoms are used. Examples of the alkenylbenzenes used in the present invention include styrene, α-methylstyrene, and vinyltoluene. Such alkenylbenzenes and (meth)
When using a monomer consisting of a mixture with acrylic acid alkyl esters, (meth)acrylic acid The proportion of alkyl ester used is preferably 10% by weight or more. The hydrophobic acrylic resin preferably contains alkenylbenzenes in an amount of 70% by weight or less. In the hydrophobic acrylic resin of the present invention, monomers consisting of alkyl (meth)acrylates or a mixture of alkyl (meth)acrylates and alkenylbenzenes as described above are all monomers to be polymerized. Among them, if the total content is at least 60% by weight, but less than 60% by weight, the formed coating film will not have sufficient water resistance and will not be able to exhibit lasting antifogging performance. Other copolymerizable α,β- used in the present invention
Ethylenically unsaturated monomers include, for example, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, etc.
β-ethylenically unsaturated carboxylic acids; α,β-ethylenically unsaturated sulfonic acids such as ethylene sulfonic acid; 2-acrylamido-2-methylpropanoic acid; α,β-ethylenically unsaturated phosphonic acids; (meth) These include hydroxyl group-containing vinyl monomers such as hydroxyethyl acrylate; acrylonitriles; acrylamides; and glycidyl (meth)acrylate esters. These monomers may be used alone or in combination of two or more types, and may have a concentration of 0 to 40
It can be used in a range of % by weight. If it exceeds 40% by weight, it is not preferable because it reduces the antifogging performance. Aqueous emulsions of hydrophobic acrylic resins can be produced by conventional emulsion polymerization methods. For example, it can be obtained by emulsion polymerizing the above monomers in an aqueous medium in the presence of a surfactant. The surfactants used in the production of the hydrophobic acrylic resin in the present invention by emulsion polymerization include the following anionic surfactants,
There are cationic surfactants and nonionic surfactants. Examples of anionic surfactants include fatty acid salts such as sodium oleate and potassium oleate; higher alcohol sulfate esters such as sodium lauryl sulfate and ammonium lauryl sulfate; alkylbenzenes such as sodium dodecylbenzene sulfonate and sodium alkylnaphthalene sulfonate. Sulfonates and alkylnaphthalene sulfonates; naphthalene sulfonic acid formalin condensates; dialkyl sulfosuccinates; dialkyl phosphate salts; polyoxyethylene sulfates such as sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, etc. There are ate salts, etc. Examples of cationic surfactants include ethanolamines; amine salts such as laurylamine acetate, triethanolamine monostearate formate, stearamide ethyl diethylamine acetate; lauryl trimethylammonium chloride, stearyl trimethylammonium chloride, dilauryl; Examples include quaternary ammonium salts such as dimethylammonium chloride, distearyldimethylammonium chloride, lauryldimethylbenzylammonium chloride, and stearyldimethylbenzylammonium chloride. Examples of nonionic surfactants include polyoxyethylene higher alcohol ethers such as polyoxyethylene lauryl alcohol, polyoxyethylene lauryl ether, and polyoxyethylene oleyl ether; polyoxyethylene octylphenol, polyoxyethylene nonylphenol, etc. Polyoxyethylene alkylaryl ethers; polyoxyethylene acyl esters such as polyethylene glycol monostearate; polypropylene glycol ethylene oxide adducts; polyoxyethylene sorbitan such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan monostearate These include fatty acid esters; sugar esters; cellulose ethers, etc. These may be used alone or in combination, but there are restrictions depending on the type of inorganic substance to be blended. That is, combinations of silica sol and cationic surfactant, which are generally negatively charged in aqueous solution, and alumina sol, which is generally positively charged in aqueous solution, and anionic surfactant, should be avoided. These combinations tend to cause gelation of the sol and agglomeration/separation of the antifogging agent composition, making application difficult. These surfactants can be used in an amount of 0.1 to 10% by weight based on the total amount of monomers charged. If it exceeds 10% by weight, it is not preferable because it reduces the water resistance of the dried coating film. Examples of the polymerization initiator used in the copolymerization reaction in the present invention include persulfates such as ammonium persulfate and potassium persulfate; organic peroxides such as acetyl peroxide and benzoyl peroxide. These are used in an amount of 0.1 to 10% by weight based on the total amount of monomers charged. In the polymerization method for obtaining the hydrophobic acrylic resin of the present invention, the monomer may be introduced in a batch manner or in a continuous feeding manner. Alternatively, a method may be adopted in which a portion is first polymerized and then the remaining portion is continuously fed. Although the monomers to be continuously fed may be fed as they are, it is extremely preferable to feed the monomers as a monomer dispersion using water and a surfactant. The water-based emulsion of hydrophobic acrylic resin, which is a component of the antifogging agent composition used in the present invention, is
The aqueous emulsion obtained by emulsion polymerization as described above can be used as it is, or it may be diluted by adding a liquid dispersion medium as described below. Alternatively, a polymer produced by emulsion polymerization may be collected separately and redispersed in a liquid dispersion medium to form an aqueous emulsion. The hydrophobic acrylic resin used in the present invention must have a glass transition temperature (Tg) within the range of 35 to 80°C. Such Tg resin is
It can be obtained by selecting the type and amount (compounding amount) of the monomers used. However, if the Tg of the acrylic resin used exceeds 80°C, it is difficult to obtain a transparent and uniform coating film. In addition, when the temperature is lower than 35°C, the inorganic colloid particles tend to aggregate several times and become non-uniformly dispersed, and the inorganic colloid particles do not adhere well to the coating substrate, so the inorganic colloid particles become a base material over time. It may fall off the surface of the material, impairing its anti-fog performance. The inorganic colloidal sol, which is an active ingredient of the antifogging agent composition used in the present invention, also functions to impart hydrophilicity to the surface of a hydrophobic polyethylene terephthalate film by applying it to the surface of the film. As the inorganic colloidal sol, for example, inorganic aqueous colloidal particles such as silica, alumina, water-insoluble lithium silicate, iron hydroxide, tin hydroxide, titanium oxide, barium sulfate, etc. can be dispersed in water or a hydrophilic medium by various methods. Another example is an aqueous sol. Among them, silica sol and alumina sol are preferred. These may be used alone or in combination. The inorganic colloidal sol preferably has an average particle size in the range of 5 to 100 mμ. Further, two or more types of colloidal sols having different average particle diameters may be used in combination. If the average particle diameter exceeds 100 mμ, the coating film becomes white and devitrified, which is not preferable. Moreover, when it is less than 5 mμ, it is not preferable because the inorganic colloidal sol lacks stability. The inorganic colloidal sol preferably has a solid content weight ratio of 0.5 to 4 based on the acrylic resin. When it exceeds 4, not only the antifogging effect does not improve in proportion to the amount blended, but also, if the film is transparent, the coating film formed after application becomes cloudy and reduces the light transmittance, which is not preferable. Furthermore, the coating film tends to become rough and brittle. On the other hand, when it is less than 0.5, sufficient antifogging effect cannot be exhibited, which is not preferable. Water resistance is further improved when a crosslinking agent is further added to the antifogging agent composition used in the present invention. That is,
This crosslinking agent allows acrylic resins to crosslink with each other, thereby improving water resistance. Crosslinking agents used for this purpose include phenolic resins, amino resins, amine compounds,
Examples include aziridine compounds, azo compounds, isocyanate compounds, epoxy compounds, and silane compounds, with amine compounds, aziridine compounds, and epoxy compounds being particularly preferred. Examples of amine compounds include aliphatic polyamines such as diethylenetriamine, triethylenepentamine, and hexamethylene diamine; alicyclic amines such as 3-3'-dimethyl 4,4'-diaminodicyclohexylmethane and isophorone diamine; 4,4' -Aromatic amines such as diaminediphenylmethane and m-phenylenediamine are used. As aziridine compounds, tris-2,
4,6-(1-aziridinyl)-1,3,5-triazine, trimethylolpropane-tri-β-aziridinylpropionate, tris[1-(2-
methyl)aziridinyl]phosphine oxide, hexa[1-(2-methyl)-aziridinyl]triphosphatriazine, etc. are used. As epoxy compounds, bisphenol A
or reaction product of bisphenol F and epichlorohydrin, phenol (or substituted phenol)
Epoxidized novolac resins formed by the reaction of epichlorohydrin with the resin reaction product of formaldehyde and formaldehyde, epichlorohydrin and aliphatic polyhydric alcohols such as glycerol, 1,4-
Resins such as those obtained by epoxidation with peracetic acid and resinous reaction products formed from butanediol, poly(oxypropylene) glycol or similar polyhydric alcohol components are used. For epoxy compounds, it is preferable to further use tertiary amines or quaternary ammonium salts as a catalyst. These crosslinking agents can be used in an amount of 0.1 to 30% by weight based on the solid content of the acrylic resin.
In particular, a range of 0.5 to 10% by weight is preferred. The liquid dispersion medium added to the antifogging agent composition used in the present invention includes water-containing hydrophilic or water-miscible solvents, such as water; monohydric alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol; ;Polyhydric alcohols such as ethylene glycol, diethylene glycol, and glycerin;
Examples include cyclic alcohols such as benzyl alcohol; cellosolve acetates; ketones and the like. These may be used alone or in combination, but the dispersion stability of the antifogging agent composition used in the present invention, the wettability after coating on the film surface, the difficulty of removing the liquid dispersion medium, and the economic efficiency should be taken into consideration. It is preferable to decide accordingly. The antifogging agent composition used in the present invention may further contain additives such as an antifoaming agent, a plasticizer, a film forming aid, a thickener, a pigment, and a pigment dispersant, if necessary. The antifogging agent composition used in the present invention can be applied to the surface of a polyethylene terephthalate film, and the liquid dispersion medium can be volatilized by forced drying or natural drying. As a method of forced drying, a hot air drying method, an infrared radiation method, etc. can be adopted. The heating temperature during forced drying is determined by the applied antifogging agent composition, but is usually selected from within the range of 50 to 250 ° C.
Preferably it is in the range of 70 to 200°C. The antifogging agent composition used in the present invention can be applied to the film surface by any known method such as roll coating, dip coating, brush coating, spray coating, bar coating, knife coating, etc. Good too. After applying the antifogging agent composition to the surface of the film and drying and volatilizing the liquid dispersion medium, the amount of solid matter deposited is usually 0.01 to 10 g/m ² , preferably 0.1 to 5 g/m 2 .
g/m ² range. If the adhesion between the film surface and the coating derived from the antifogging agent composition used in the present invention is insufficient, the film surface may be subjected to plasma treatment before applying the antifogging agent composition, or The surface of the film may be modified by a method such as corona discharge treatment. In order to improve the dust resistance, fog resistance, weather resistance, and blocking resistance of the agricultural polyethylene terephthalate film according to the present invention, other resins are added to the film surface on which the antifogging agent coating according to the present invention is not applied. For example, a coating layer made of acrylic resin, fluorine resin, or polyolefin resin may be provided. Note that the above-mentioned ultraviolet absorber may be included in this coating layer. (Effects of the invention) The present invention has the following particularly remarkable effects,
The industrial value is extremely large. (1) The agricultural polyethylene terephthalate film according to the present invention has extremely excellent water resistance because it has a coating film made of an antifogging agent containing a hydrophobic acrylic resin. (2) The agricultural polyethylene terephthalate film according to the present invention has a coating film made of an antifogging agent containing an inorganic colloidal sol, so it is excellent in non-adhesion, surface hardness, and water resistance. (3) The agricultural polyethylene terephthalate film according to the present invention has an anti-fog coating consisting of an acrylic resin of a specific composition with a glass transition temperature in the range of 35 to 80°C and an inorganic colloidal sol, so it has extremely excellent anti-fog properties. It shows stable anti-fog properties even under high temperature and high humidity conditions. Furthermore, the polyethylene terephthalate film that is the base material contains an ultraviolet absorber, which allows the antifogging performance of the antifogging coating film of the present invention to last for a long period of time. (Examples) Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Examples 1 to 8, Comparative Examples 1 to 7 (1) Preparation of base film For 100 parts by weight of polyethylene terephthalate (having an intrinsic viscosity of 0.65 measured at 25°C using o-chlorophenol as a solvent), The ultraviolet absorbers shown in the table were also blended at the blending ratios shown. After stirring and mixing each formulation in a super mixer for 10 minutes, they were melt-extruded using a conventional method, stretching in the longitudinal direction at a temperature of 65°C and a stretching ratio of 3.5 times, and then stretching in the transverse direction at a temperature of 65°C and a stretching ratio of 3.5 times. biaxially stretched,
A biaxially oriented film with a thickness of 0.15 mm was produced. The density of this film was 1.37 g/cm ³ . (2) Preparation of antifogging composition A four-neck flask was charged with 2 parts by weight of polyoxyethylene lauryl ether and 80 parts by weight of water, heated to 60°C under a stream of nitrogen gas, and 0.5 parts by weight of ammonium persulfate was added thereto. 100 parts by weight of a mixture of each monomer shown in Table 1 was added dropwise over 3 hours. The reaction temperature at this time is kept in the range of 60 to 70℃, but the temperature remains within the same range even after the dropwise addition.
After holding for a certain period of time, the mixture was cooled and neutralized with aqueous ammonia to obtain an acrylic resin emulsion. The glass transition temperature of each resin was as shown in Table 1. Various antifogging agent compositions were prepared by blending the acrylic resin emulsion thus obtained with inorganic colloidal sols and the like in the types and amounts shown in Table 1. However, as a comparative example, an antifogging agent composition containing no inorganic colloidal sol or acrylic resin was also prepared. (3) Formation of a coating film using an antifogging agent composition The various antifogging agent compositions obtained in (2) were coated on one side of the polyethylene terephthalate film obtained in (1) by bar coating, after drying. The coating was applied so that the coating amount was 0.5 g/m ² as solid content, and the solution was left in hot air at 80° C. for 1 minute to scatter the solvent. (4) Evaluation of polyethylene terephthalate film Various properties of the polyethylene terephthalate film obtained in (3) were evaluated by the methods described below. Adhesion Cellophane tape is adhered to the coated surface of each film, and when this cellophane tape is peeled off,
The peeling status of the paint film was observed with the naked eye. The results are shown in Table 2. The evaluation criteria are as follows. 〇...The paint film did not peel off at all and remained completely. 〇x...More than 2/3 of the coating film remains without peeling off. △……More than 2/3 of the paint film has peeled off. ×...The paint film has completely peeled off. Anti-fogging test Each film was installed in a single-roof greenhouse (1.8m wide, 18m deep, 2m high, roof slope 30°) in a test field in Ama District, Aichi Prefecture, with the coated surface inside the greenhouse. The antifogging properties were periodically evaluated with the naked eye. The results are shown in Table 2. The evaluation criteria are as follows. ◎...Water adheres in a thin film and no water droplets are observed. 〇…Water is attached in a thin film, but slightly large water droplets are observed. ○x: Water is attached in a thin film, but large water droplets are observed to be attached in some areas. △……A state in which small water droplets are observed to be partially attached. ×: Condition in which fine water droplets are observed on the entire inner surface of the film.

【table】

[Table] A crosslinking agent containing a compound as an active ingredient.

[Table] The following is clear from Table 2. (1) The agricultural polyethylene terephthalate film of the present invention has excellent antifogging properties, especially long lasting antifogging properties, and even after 36 months, it maintains the good antifogging properties almost at the initial stage of expansion. (2) Even if the antifogging agent composition of the present invention is applied, if the base film, ie, a polyethylene terephthalate film, does not contain an ultraviolet absorber, the antifogging durability will be poor. (Comparative Example-1) (3) When the glass transition temperature of the acrylic resin contained in the antifogging agent composition is less than 35°C, the antifogging durability is poor. (Comparative Example-2) Conversely, when the glass transition temperature is 80° C. or higher, the adhesion of the anti-fog coating to the film is poor and the anti-fog durability is also poor. (Comparative Example-3) (4) If the hydrophobic acrylic resin in the acrylic resin contained in the antifogging agent composition is less than 60% by weight, the adhesion to the film of the antifogging coating will be poor. Anti-fog durability is also poor. (Comparative Example 4) (5) If either one of the two components constituting the antifogging agent composition, ie, the acrylic resin and the inorganic colloidal sol, is missing, the antifogging properties will be very poor.
(Comparative Examples 5 and 6) (6) Commercially available agricultural polyethylene terephthalate films have poor anti-fog durability. (Comparative Example-7) Comparative Example 8 In this comparative example, the following acrylic anionic polymer insoluble in water and soluble in organic solvents was first applied to the surface of the polyethylene terephthalate film on which antifogging properties were to be imparted. An antifogging film was produced by forming an electrolyte coating, and then a positively charged alumina sol coating thereon, and its performance was evaluated. That is, the following composition (hereinafter, parts are parts by weight): Methyl methacrylate 60 parts Butyl methacrylate 30 parts Methacrylic acid 10 parts Penzoyl peroxide 0.5 parts Isopropanol 300 parts were charged into a flask and heated at a temperature of 80°C under a nitrogen atmosphere. After polymerizing for 7 hours, add sodium hydroxide in an amount to neutralize half of the methacrylic acid component.
The above polymer was made into an electrolyte. Isopropanol was added to this to obtain an acrylic anionic polymer electrolyte A having a solid content of 13% by weight. On the other hand, 1 part of alumina sol was uniformly dispersed in 100 parts of water to obtain an antifogging agent composition B containing alumina sol as an active ingredient. First, the above-mentioned polymer electrolyte A
was applied using the bar coating method, dried with hot air at 90℃,
The amount of solid content after drying was 0.25 g/m ² . Next, the above-mentioned antifogging agent composition B was applied to the coated film surface by a bar coating method, and dried with hot air at 90° C., so that the solid content after drying was 0.25 g/m ² . This product was evaluated in the same manner as in the above examples. The results are shown in Table 3 below. Table 3 Adhesion of coating film 〇x Anti-fogging property After 1 month 〇 After 6 months 〇 After 12 months 〇x After 18 months △ After 24 months △ After 36 months × As above, first apply acrylic to the polyethylene terephthalate film surface. The antifogging function of a coating film formed by forming a coating film of an anionic polymer electrolyte and then a coating film made of positively charged alumina sol is inferior to that of the coating film of the present invention.

Claims (1)

[Claims] 1. On one or both sides of an agricultural polyethylene terephthalate film containing an ultraviolet absorber, (a) 60 to 100% by weight of a monomer consisting of an alkyl ester of acrylic acid or methacrylic acid or a monomer of acrylic acid Alternatively, a mixed monomer of alkyl esters of methacrylic acid and alkenylbenzenes and 0 to 40% by weight of other α,β-ethylenically unsaturated monomers that can be copolymerized with the above monomers are emulsified. (a) one or more water-based emulsions of hydrophobic acrylic resins having a glass transition temperature in the range of 35 to 80°C obtained by polymerization; and (b) one or more inorganic colloidal sols.
and (b), or an antifogging agent composition containing a mixture of the above two components (a) and (b), a crosslinking agent, and/or a liquid dispersion medium. Agricultural polyethylene terephthalate film coated with