JPH042101B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyethylene terephthalate film for agricultural use. More specifically, 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. In general, polyethylene terephthalate film is known to exhibit high crystallinity, high melting point, heat resistance and chemical resistance, and also to exhibit excellent mechanical properties such as strength and elastic modulus. For this reason, polyethylene terephthalate film is used for magnetic tape, photography, electricity, etc.
It is widely used for metallization, packaging, agriculture, etc. However, this film has the property of absorbing ultraviolet rays, particularly ultraviolet rays of 320 nm or less, and has the disadvantage that when this film is extended outdoors for a long period of time, its mechanical properties deteriorate significantly. In order to improve the weather resistance of this film, it is possible to form the film after adding an ultraviolet absorber, or to tightly bond the ultraviolet absorber to the film surface, as described in Japanese Patent Publication No. 46-24160. Are known. In the former method, the ultraviolet absorber is uniformly mixed and dispersed in the resin. However, according to this method, harmful light rays are gradually absorbed and weakened as they pass from the incident side to the opposite side as they pass through the film.
The side of the film on which the light rays are incident will be harmed by harmful rays, and the weather resistance of the film cannot be sufficiently improved. The latter method can produce a film with better weather resistance than the former method, but it is difficult to bond the UV absorber firmly to the film surface at a uniform concentration, and it is difficult to bond the UV absorber firmly to the film surface when exposed to sunlight for long periods of time outdoors. It has been difficult to impart sufficient weather resistance to withstand stretching and outdoor exposure. Under these circumstances, the inventors of the present invention have made extensive studies in order to provide an agricultural polyethylene terephthalate film whose mechanical properties do not deteriorate even if it is stretched outdoors or exposed for long periods of time. ,
The idea was completed earlier (Utility Model Publication No. 159239, Showa 56).
The agricultural polyethylene terephthalate film according to this invention has excellent weather resistance, and even if it is exposed outdoors for a long period of time, the decrease in mechanical strength, transparency, etc. is extremely small. By the way, when spreading agricultural plastic film in greenhouses or tunnels, it depends on the spreading method, the structure of the greenhouse or tunnel, the location and direction in which these are installed, the weather conditions at the time of spreading, etc. The film may be bent or blown away by the wind. In such cases, a film is formed on the surface of the plastic film, and if this film has poor elasticity and impact resistance, cracks are likely to occur in the film. This causes problems in practical use, such as causing whitening of the coating or peeling of the coating. In order to improve the impact resistance of a film made of acrylic resin, increase the proportion of components that improve the flexibility of the acrylic resin, such as acrylic ester, and raise the glass transition temperature (Tg) of the resin. It has been experimentally determined that the lower the value, the better. However, if the Tg is set too low, the problem arises that blocking (mutual adhesion) of this film tends to occur, and it is difficult to balance impact resistance and blocking resistance. In view of this situation, the inventors of the present invention have developed a film that does not whiten or peel off even under harsh conditions during spreading, and has excellent mechanical strength and weather resistance (light resistance). However, as a result of intensive studies to provide an agricultural polyethylene terephthalate film that can withstand long-term outdoor expansion, the present invention has been completed. Therefore, the gist of the present invention is that a thickness of 0.01
Agricultural polyethylene terephthalate film of ~0.3 mm is coated with a 1-10 micron thick acrylic resin film containing a UV absorber on one side. In the presence of system elastic particles, a methacrylic acid alkyl ester monomer or a methacrylic acid alkyl ester as a main component,
It contains a graft copolymer having a crosslinked acrylate ester-based elastomer as a backbone obtained by polymerizing a mixture of this and a copolymerizable vinyl compound monomer, and the crosslinked acrylic resin in the acrylic resin A polyethylene terephthalate film for agricultural use, characterized in that the proportion of acid ester elastomer is 5 to 80% by weight, and the amount of ultraviolet absorber blended is 10 to 25 parts by weight per 100 parts by weight of acrylic resin. exists in 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 in which 85% or more of the repeating units are polyethylene terephthalate units and the remainder is other components. Terephthalate, polyethylene terephthalate, 85% by weight or more, remaining 15% by weight
The following includes polymer blends that are other polymers. 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, etc., if necessary. The agricultural polyethylene terephthalate film according to the present invention is biaxially stretched. 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. The agricultural polyethylene terephthalate according to the present invention is biaxially stretched by 2.0 to 5.0 times. If the stretching ratio is less than 2.0 times, the strength of the product will not be sufficient, so it is not preferable. If it exceeds 5.0 times, the strength of the product will be sufficient, but it will be difficult to manufacture, so it is not preferable. The stretching ratio is 2.5 in both directions.
A range of ˜4.0 times is particularly preferred. The agricultural polyethylene terephthalate according to the present invention preferably has a thickness of 0.01 to 0.3 mm. Thickness
If it 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. The agricultural polyethylene terephthalate film according to the present invention has an acrylic resin film containing an ultraviolet absorber formed on one side thereof. In the present invention, the acrylic resin refers to a methacrylic acid alkyl ester monomer or a vinyl compound monomer copolymerizable with the methacrylic acid alkyl ester as a main component in the presence of a crosslinked acrylic ester elastomer. A graft copolymer obtained by polymerizing a mixture of acrylic acid ester and acrylic acid ester, which contains 5 to 80% by weight of the crosslinked acrylic ester elastomer. The acrylic acid alkyl ester preferably has an alkyl group having 1 to 8 carbon atoms, and may be either linear or branched. Specific examples thereof include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, etc., and these can also be used in combination. Vinyl compound monomers copolymerizable with these acrylic acid alkyl esters include methacrylic acid and methacrylic acid alkyl esters (alkyl group having 1 to 12 carbon atoms), itaconic acid dialkyl esters (alkyl group having 1 to 12 carbon atoms), and itaconic acid dialkyl esters (alkyl group having 1 to 12 carbon atoms). 10), acrylonitrile, methacrylonitrile, vinyl chloride,
Examples include vinylidene chloride, styrene, nuclear alkyl-substituted styrene, and α-methylstyrene. These monomers are not more than 40% by weight, preferably 25% by weight
The following should be used. As the crosslinkable monomer, those commonly used as polyfunctional compounds may be used, and specific examples include ethylene glycol dimethacrylate, 1,
3-butylene glycol dimethacrylate, 1,
4-butylene glycol dimethacrylate, propylene glycol dimethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethanetetramethacrylate, dipropylene glycol dimethacrylate, divinylbenzene, divinyl acypate, diallyl phthalate,
Examples include diallyl maleate, allyl acrylate, allyl methacrylate, triallyl cyanurate, and two or more of these may be used in combination. The crosslinked acrylic ester elastomer is preferably produced by emulsion polymerization. Polymerization initiators that can be used in this case are common free radical generating initiators. Specific examples include inorganic peroxides such as potassium persulfate and ammonium persulfate;
Organic hydroperoxides such as kyumene hydroperoxide, p-menthane hydroperoxide, ditertiary butyl hydroperoxide; organic peroxides such as benzoyl peroxide, lauroyl peroxide, kyumene peroxide, azobisisobutyro Examples include azo initiators such as nitriles. Furthermore, conventional redox initiators which are a combination of these and a reducing agent such as sodium sulfite, acidic sodium sulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate, glucose, polyamine, or hydroxyacetone ascorbate may also be used. Emulsifiers that can be used include common surfactants for emulsion polymerization. For example, anionic surfactants such as sodium, potassium, and ammonium salts of alkyl sulfates having 8 to 20 carbon atoms and sodium, potassium salts of aliphatic carboxylic acids such as lauric acid, stearic acid, and palmitic acid;
Examples include nonionic surfactants such as alkylphenols, aliphatic alcohols, and reaction products of polypropylene oxide and ethylene oxide. Further, in some cases, two or more of these surfactants can be used in combination. Furthermore, surfactant aids such as naphthalene formaldehyde condensed sulfonate salts can also be added. Furthermore, if necessary, cationic surfactants such as alkylamine hydrochlorides can also be used. The following method can be used to produce a crosslinked acrylic ester elastomer by emulsion polymerization. (1) Produced by emulsion polymerization by adding a small amount of crosslinking monomer to an acrylic acid alkyl ester monomer or a mixture of an acrylic acid alkyl ester and a vinyl compound monomer copolymerizable therewith. how to. (2) Add an acrylic acid alkyl ester monomer or a mixture of an acrylic acid alkyl ester and a vinyl compound monomer copolymerizable therewith to the polymer emulsion obtained by the method of (1), and apply the emulsion polymerization method. A method of manufacturing. (3) In the method of (2), a small amount of crosslinking agent is added to the monomer or monomer mixture, and the product is produced by emulsion polymerization. (4) First, an uncrosslinked elastic body is produced by an emulsion polymerization method from an acrylic acid alkyl ester monomer or a mixture of an acrylic acid alkyl ester and a vinyl compound monomer copolymerizable therewith. Next, an acrylic acid alkyl ester monomer, or a mixture of an acrylic acid alkyl ester and a vinyl compound monomer copolymerizable therewith, and a small amount of a crosslinking monomer are added to this polymerization system, and an emulsion polymerization method is carried out. A method of manufacturing by. (5) Add an acrylic acid alkyl ester monomer or a vinyl compound monomer copolymerizable with an acrylic acid alkyl ester to one of the polymer emulsions obtained by the methods (1) to (4), and crosslink it. A method of manufacturing by emulsion polymerization without adding or adding a small amount of a monomer. The crosslinked acrylate ester-based elastomer is produced by adjusting the average particle diameter of the crosslinked elastomer emulsion particles by adjusting the amount of the surfactant used and the amount of the aqueous medium used. It is important to have a range. If it is less than 0.05 micron, the mechanical strength of the acrylic resin used as the coating will decrease, and if it exceeds 0.30 micron, stress whitening will become significant, which is not preferable. The crosslinked acrylic ester-based elastic body preferably has a gel content of 80% or more and a swelling degree of 15 or less as measured by the following method, regardless of which method is used. The swollen weight after taking a predetermined amount of crosslinked elastic body _W0 and immersing it in methyl ethyl ketone for 48 hours at room temperature
W ₁ and the weight W ₂ after drying this sample in a vacuum dryer are measured and calculated using the following formula. Gel content = W ₂ / W ₀ × 100 (%) Swelling degree = W ₁ − W ₂ / W ₀ Gel content and swelling degree are determined by adjusting the type and amount of the crosslinking monomer mentioned above, as well as adjusting the elastic body components. It is affected by polymerization conditions such as the temperature during polymerization, the type and amount of initiator used, the method of adding monomers constituting the elastomer component, and the presence or absence of a molecular weight regulator, so adjust it accordingly. It is better. When the gel content is less than 80%, the film-forming acrylic resin obtained from the elastic body will completely dissolve in the organic solvent described below or will swell excessively, deforming the elastic body particles. This is not preferred because it loses its ability to improve mechanical strength, especially impact resistance. Regarding the degree of swelling, if it exceeds 15, stress whitening tends to occur, which is not preferable. The monomer to be grafted onto the crosslinked acrylic ester elastomer is a mixture of a methacrylic acid alkyl ester or a methacrylic acid alkyl ester as a main component, and a vinyl compound monomer that can be copolymerized with the monomer. The methacrylic acid ester as a component to be grafted may be selected from those mentioned above used in the production of the elastomer, and vinyl compound monomers copolymerizable with it may also be used in the production of the elastomer. You may choose from the examples given. In this case, the type of monomer,
It is important to choose the combination. When Tg is less than 50°C, the blocking resistance of the polyethylene terephthalate film formed with the acrylic resin film containing the graft polymer deteriorates (blocking easily occurs), which is not preferable. The graft polymerization reaction is preferably carried out by emulsion polymerization, but may also be carried out by solution polymerization. When using the emulsion polymerization method, for example, the monomer to be grafted is added to an emulsion of a crosslinked acrylic acid ester elastomer, and if necessary, an emulsifier, a polymerization initiator, a molecular weight regulator, water, etc. are added, and the usual process is carried out. The conditions for emulsion polymerization can be selected and carried out. When carrying out the graft polymerization reaction, the ratio of the crosslinked elastic body to the monomer to be grafted is 10 to 90 parts by weight, based on the polymer solid content of the crosslinked elastic body emulsion.
It is preferable to select from a range of 90 to 10 parts by weight of the monomer to be grafted. The graft polymer can be used as a film-forming acrylic resin as it is, or by blending it with a transparent hard thermoplastic resin that is compatible with the graft polymer and has a Tg of 50°C or higher. In the latter case, when blending, the proportion of the crosslinked elastic body contained in the acrylic resin is 5 to 80% by weight,
It is preferably in the range of 10 to 50%. If the proportion of the crosslinked elastic material is less than 5% by weight, the mechanical strength will be poor, and if it exceeds 80% by weight, the blocking resistance of the film containing it as a coating will be poor, which is not preferable. The acrylic resin is blended with an ultraviolet absorber to form a film on one side of the base film. The types of ultraviolet absorbers to be added to these acrylic resins 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, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2' among benzophenone compounds -dihydroxy-4,4'-dimethoxybenzophenone is preferred, and 2-(2'-hydroxy-
Particularly preferred is 5'-tertiary-butylphenyl)benzotriazole. These may be used alone or in combination of two or more. If the amount of the ultraviolet absorber added to the acrylic resin is too small, the object of the present invention will not be achieved, and if it is too large, there will be a problem of bleed-out. The preferred blending amount is acrylic resin
The amount ranges from 10 to 25 parts by weight per 100 parts by weight. If the thickness of the acrylic resin film containing these ultraviolet absorbers is too thin, the object of the present invention will not be achieved, so it is undesirable, and if it is too thick, the problem arises that the film is likely to peel off. The thickness of the film is preferably in the range of 1 to 10 microns, particularly preferably in the range of 1 to 5 microns. The amount of UV absorber blended into the acrylic resin and the thickness of the film formed on one side of polyethylene terephthalate can be varied, but the amount of UV absorber per fixed area of the film is 150 to 1000.
A range of mg/m ² is particularly preferred. To manufacture the agricultural polyethylene terephthalate film according to the present invention, first, biaxially stretched polyethylene terephthalate is manufactured. Next, one side of this biaxially stretched polyethylene terephthalate film is coated with one of ketones such as methyl ethyl ketone, aromatic hydrocarbons such as benzene, toluene, and xylene, and acetate esters such as methyl acetate and ethyl acetate. Alternatively, a solution in which an acrylic resin and an ultraviolet absorber are dissolved is applied to an organic solvent that is a mixture of two or more types, and the organic solvent is volatilized to form an acrylic resin film containing an ultraviolet absorber. Suitable coating methods include commonly used gravure coating methods, reverse coating methods, and spray methods. Hereinafter, the present invention will be explained in detail based on the drawings. FIG. 1 is a cross-sectional view of an example of the agricultural polyethylene terephthalate film according to the present invention, and FIG. 2 is a cross-sectional view of the film according to the present invention when sunlight hits the film from the side where the acrylic resin film is provided.
Figure 3 is a model diagram showing the transmission of ultraviolet rays when sunlight is applied to a conventional polyethylene terephthalate film in which an ultraviolet absorber is uniformly dispersed throughout the film. FIG. In the figure, 1 and 21 are polyethylene terephthalate films, 2 and 22 are acrylic resin films containing an ultraviolet absorber, and 31 are polyethylene terephthalate films containing an ultraviolet absorber. The agricultural polyethylene terephthalate film according to the present invention has a film 2 of an acrylic resin containing an ultraviolet absorber formed on one side thereof. When this film is used for actual agricultural purposes, the acrylic resin film 2 is placed on the outside, and the film is used so that sunlight hits this surface. When used in this way, as schematically shown in FIG. 2, the ultraviolet rays hit the film with an intensity of Iin, and most of it is absorbed by the acrylic resin film 22.
It has a strength of Iout and can penetrate polyethylene terephthalate film at this strength. On the contrary,
In the conventional film made by kneading an ultraviolet absorber into it, as shown schematically in Figure 3, the ultraviolet rays that hit the film at an intensity of Iin are gradually absorbed as they pass through the film. Made to the strength of Iout. Such differences in the absorption state of ultraviolet rays have a large effect on the weather resistance of the film. The agricultural polyethylene terephthalate film according to the present invention exhibits the following effects and has extremely great industrial utility value. When the agricultural polyethylene terephthalate film according to the present invention is spread outdoors, the ultraviolet rays in the sunlight are absorbed as shown in FIG. As such, most of it is absorbed by the film made of acrylic resin. As a result, polyethylene terephthalate film will not be affected by ultraviolet rays, will not develop small cracks on its surface, and will not turn yellow or turn white even if it is stretched or exposed outdoors for a long time. There's nothing to do. The effect of preventing deterioration of weather resistance and transparency is
This is extremely remarkable compared to other methods in which a UV absorber is added to form a film or a method in which the UV absorber is tightly bonded to the film surface. In the polyethylene terephthalate film according to the present invention, the acrylic resin film formed on one side contains a crosslinked elastic body and has mechanical strength.
In particular, since it has excellent impact resistance, cracks are less likely to occur even when subjected to impact, and therefore, film whitening and film peeling due to cracks are less likely to occur. The polyethylene terephthalate film according to the present invention has excellent adhesion to the film made of acrylic resin formed on one side, and since this film is extremely thin, the film does not peel off. The acrylic resin formed on one side of the polyethylene terephthalate film according to the present invention is
Compared to other resins, even if a large amount of UV absorber is blended, there is less problem of bleed-out, and it is suitable for forming a film containing a UV absorber. The film made of acrylic resin formed on one side of the polyethylene terephthalate film according to the present invention itself has excellent weather resistance, so it is not easily deteriorated by ultraviolet rays and does not have any adverse effect on the polyethylene terephthalate film that is the base material. do not have. Due to its characteristics, the film made of acrylic resin is not sticky and attracts little dust, which contributes to maintaining transparency and transmittance for a long period of time. Therefore, the film according to the present invention is suitable for agricultural applications. be. 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 10 (1) Base polyethylene terephthalate film stretched 3.5 times both lengthwise and widthwise, with a density of 1.392
g/cm ³ , thickness 125μ. (2) Preparation of acrylic resin An acrylic resin solution for blending the ultraviolet absorber was prepared as follows. 1 Preparation of acrylic resin solution A Production of crosslinked elastic body In a polymerization vessel, 300 parts by weight of deionized water (hereinafter simply expressed as "parts" means "parts by weight") and 0.3 parts by weight of potassium persulfate. 1 part, 0.5 part of disodium phosphate dodecahydrate, and 0.3 part of sodium hydrogen phosphate dihydrate, and after sufficient nitrogen replacement, the internal temperature was raised to 70℃.
The temperature rose to . While maintaining the internal temperature at this temperature and stirring, add 19.8 parts of styrene and 69.3 parts of butyl acrylate.
A mixture of 2.5 parts of allyl methacrylate, 0.9 parts of allyl methacrylate, and 2.5 parts of sodium dioctyl sulfosuccinate (emulsifier) was added continuously over a period of 2 hours. Immediately after the addition is complete, add t-butylperoxy-2
- 1.0 parts of ethylhexanoate, 2.2 parts of styrene,
A mixture consisting of 7.7 parts of butyl acrylate and 0.1 part of allyl acrylate was added. After 30 minutes had elapsed from the end of the addition, the internal temperature was raised to 90°C, and the reaction was continued at this temperature for 3 hours to obtain an emulsion of a crosslinked elastic body. The average particle diameter of this crosslinked elastic body was 0.20 microns, the gel content was 97.1%, and the degree of swelling was 7.2. Production of graft copolymer 400 parts of the crosslinked elastomer emulsion obtained above was charged into a polymerization can, and while stirring, the atmosphere was replaced with nitrogen, and the internal temperature was raised to 80°C. While maintaining the internal temperature at this temperature, add a solution of 0.15 parts of sodium formaldehyde sulfoxylate in 3.0 parts of deionized water with stirring, and then add methyl methacrylate.
30.0 parts, n-octyl mercaptan 0.03 parts, paramenthane hydroperoxide (50% solution)
0.15 part of the mixture was added continuously over a period of 30 minutes. After the addition was completed, the polymerization reaction was continued for another 30 minutes to obtain a graft copolymer emulsion. The obtained graft copolymer emulsion was salted out according to a conventional method, and the polymer was separated, washed with water, and dried to obtain a graft copolymer powder. Preparation of resin solution A 13.5 parts of beads of methacrylic resin (copolymer of methyl methacrylate/ethyl methacrylate in a ratio of 96/4) were mixed with 6.5 parts of the graft copolymer obtained above, and this mixture was mixed with methyl ethyl ketone. The acrylic resin solution A having a solid content of 20% by weight was prepared by dissolving the resin in a mixed solvent of 64 parts and 16 parts of toluene with stirring. 2 Preparation of acrylic resin solution B Production of crosslinked elastic body 250 parts of deionized water, 2.0 parts of sodium dioctyl sulfosuccinate, and 0.05 parts of sodium formaldehyde sulfoxylate were placed in a polymerization tank, and the mixture was sufficiently purged with nitrogen. . While stirring the contents of this polymerization can, a mixture consisting of 1.6 parts of methyl methacrylate, 8 parts of butyl acrylate, 0.4 parts of 1,3-butylene dimethacrylate, 0.1 part of allyl methacrylate, and 0.04 parts of kyumene hydroperoxide was added. I prepared it. The temperature inside the polymerization reactor was raised to 70°C, and the reaction was continued at this temperature for 60 minutes. Next, 1.5 parts of methyl methacrylate, 22.5 parts of butyl acrylate, and 1,3-butylene dimethacrylate were added to this polymerization can.
A mixture of 1.0 part of allyl methacrylate, 0.25 part of allyl methacrylate, and 0.05% by weight of kyumene hydroperoxide based on the monomer mixture was added over a period of 60 minutes. The resulting crosslinked elastic body had an average particle diameter of 0.12 microns, a gel content of 90%, and a degree of swelling of 10. Production of graft copolymer A solution prepared by dissolving 0.01 part of sodium formaldehyde sulfoxylate in 3 parts of ionized water was added to the polymerization vessel containing the above crosslinked elastomer emulsion, and then 5 parts of methyl methacrylate and acrylic A mixture of 5 parts of butyl acrylate, 0.1 part of allyl acrylate, and 0.03% by weight of kyumene hydroperoxide based on these monomers was added over 30 minutes.
Added continuously. After the addition was completed, the polymerization reaction was continued for an additional 30 minutes. A solution prepared by dissolving 0.05 parts of sodium formaldehyde sulfoxylate in 3 parts of ionized water was added to this polymerization reactor, and the temperature was raised to 80°C. Hydroperoxide (50% solution)
A mixture consisting of 0.13 parts was added over a period of 30 minutes.
After this addition was completed, the polymerization reaction was continued at 80° C. for 30 minutes to obtain a graft copolymer emulsion. The obtained graft copolymer emulsion was salted out according to a conventional method, and the polymer was separated, washed with water, and dried to obtain a graft copolymer powder. Preparation of Resin Solution B 20 parts of the graft copolymer obtained above was placed in a mixed solvent consisting of 64 parts of methyl ethyl ketone and 16 parts of toluene and stirred to prepare acrylic resin solution B with a solid content of 20% by weight. did. 3 Preparation of acrylic resin solution C Production of crosslinked elastic body Same as in the preparation of acrylic resin solution B. Production of Graft Copolymer A graft copolymer powder was obtained in the same manner as in the preparation of acrylic resin solution B. 70 parts of this graft copolymer powder in a polymerization can,
Add 150 parts of methyl ethyl ketone, stir to dissolve the copolymer, and add 30 parts of methyl methacrylate to this.
A mixture of 1.0 parts of benzoyl peroxide and 1.0 parts of benzoyl peroxide was added thereto, the atmosphere was sufficiently purged with nitrogen, the temperature was raised to 70°C with stirring, and the polymerization reaction was carried out at this temperature for 3 hours. Preparation of Resin Solution C To the graft copolymer solution obtained above, 170 parts of methyl ethyl ketone and 80 parts of toluene were added to prepare an acrylic resin solution C having a resin solid content of 20% by weight. 4 Preparation of acrylic resin solution C After charging 200 parts of deionized water and 2.0 parts of sodium dioctyl sulfosuccinate into a polymerization tank,
Sufficient nitrogen replacement was performed. In this polymerization can, 25.5 parts of butyl acrylate, 4.5 parts of methyl methacrylate,
0.3 parts of tetraethylene glycol diacrylate,
A mixture consisting of 0.03 part of kyumene hydroperoxide was charged, and while stirring under a nitrogen gas stream,
The temperature was raised to 40°C. Thereafter, a solution of sodium formaldehyde sulfoxylate (0.1% by weight based on the monomer mixture) dissolved in a small amount of water was gradually added, and the polymerization reaction was continued for 4 hours. The obtained crosslinked elastic body had an average particle diameter of 0.17 microns, a gel content of 90.0%, and a degree of swelling of 8.0. Production of graft copolymer The temperature inside the polymerization reactor containing the above crosslinked elastic body was raised to 80°C, and 0.04 parts of sodium formaldehyde sulfoxylate was added thereto, followed by 10 parts of methyl methacrylate and 10 parts of butyl acrylate. , and 0.06 part of kyumene hydroperoxide were added continuously over a period of 2 hours, and after the addition was completed, the polymerization reaction was continued for an additional 30 minutes. After this, add 40 methyl methacrylate to the same polymerization can.
A mixture of 10 parts of butyl acrylate and 0.15 parts of kyumene hydroperoxide was added continuously over a period of 4 hours, and after the addition was completed, the polymerization reaction was continued for 30 minutes to obtain a graft copolymer emulsion. The obtained graft copolymer was salted out according to a conventional method, and the polymer was separated, washed with water, and dried to obtain a graft copolymer powder. Preparation of resin solution 20 parts of the graft copolymer obtained above was added to a mixed solution consisting of 64 parts of methyl ethyl ketone and 16 parts of toluene, stirred, and dissolved to form an acrylic resin solution D with a solid content of 20% by weight. was prepared. (3) Formation of a film containing an ultraviolet absorber Add the type of ultraviolet absorber shown in Table 1 to the acrylic resin solution prepared according to the method described in (2) above in the proportion (resin (means the ratio to solid content). After adding the solution, apply it to one side of a polyethylene terephthalate film.
It was coated by a gravure coating method, and the coated surface was heated to volatilize the solvent to form a film containing an ultraviolet absorber. Table 1 shows the thickness of this film and the amount of ultraviolet absorber per unit area of the film. (4) Properties of film before outdoor exposure Before exposing a polyethylene terephthalate film with a film containing an ultraviolet absorber to the outdoors,
The following properties were measured. The results are shown in Table 1. (a) Light transmittance at a wavelength of 340 nm Measured using a spectrophotometer (Model 323 manufactured by Hitachi, Ltd.). (b) Elongation rate Based on JIS K-6234. (c) Puncture impact strength Puncture impact tester (manufactured by Toyo Seiki Seisakusho)
Tested on a sample 10cm long and 10cm wide, and the energy at break is expressed in kg・cm. (d) Light transmittance at a wavelength of 550 nm Same as in the case of (a). (E) Visual judgment of transparency The transparency of the film is determined by observing it with the naked eye. The criteria for judgment were as follows. ○...Excellent transparency with no whitening on the surface. ○～△: Excellent transparency, with almost no whitened areas observed on the surface. △...Transparency is slightly poor, and some whitened areas are observed on the surface. △ to ×: Transparency is considerably poor, and whitened portions are considerably observed on the surface. ×...Transparency is extremely poor, and whitened areas are noticeable on the surface. (f) Adhesive strength of the film: Judgment was made by attaching cellophane tape (manufactured by Nichiban) to a polyethylene terephthalate film and visually observing changes in the film after removing the cellophane tape. The criteria for judgment were as follows. ◎...Even if the cellophane tape is removed vigorously, no change is observed in the film. ○...If you remove the cellophane tape that has been applied, a very small amount of film will be left behind, but if you peel it off slowly, no change will be observed in the film. (G) Impact resistance of the film After the film on which the film was formed was flapped for a certain period of time in a strong wind of 20 m/s as shown in the perspective view in Figure 4, cracks to the film film were observed. The occurrence of this was determined visually. In Fig. 4, 41 is a blower, 42 is a wind tunnel, and 43 is a film, each of which has a length of 330 mm and a width of 210 mm. (5) Properties of film after outdoor exposure A polyethylene terephthalate film with a film containing an ultraviolet absorber was exposed in a field in Yatabe-cho, Tsukuba-gun, Ibaraki Prefecture from November 1980 to October 1988. The following properties were measured for the resulting film. The results are shown in Table 1. The elongation rate, puncture impact strength, light transmittance at a wavelength of 550 nm, and visual judgment of transparency were the same as in the method for evaluating film properties before outdoor exposure in □. Comparative Example 1 Regarding a base polyethylene terephthalate film having the same properties as that used in Example 1, and without forming a film, various properties were measured on the film before outdoor exposure in the same manner as in Example 1, and further The film was exposed outdoors in the same manner as in the same example, and various properties of the film after outdoor exposure were measured. The results are shown in Table 1. Comparative Example 2 A film of acrylic resin solution C containing no ultraviolet absorber was formed on one side of a base polyethylene terephthalate film having the same properties as those used in Example 1. Regarding this film, as in Example 1, various properties were measured on the film before outdoor exposure, and then the film was exposed outdoors in the same manner as in the same example, and various properties were measured on the film after outdoor exposure. did. The results are shown in Table 1. Comparative Example 3 100 parts by weight of raw material polyethylene terephthalate,
0.34 parts by weight of 2-(2'-hydroxy-5'-tertiary-butylphenyl)benzotriazole was blended. This compound was made into a film by a known method and stretched 3.5 times both lengthwise and widthwise to reduce the density.
A film having a weight of 1.392 g/cm ³ and a thickness of 125 μm was obtained. Regarding this film, as in Example 1, various properties were measured on the film before outdoor exposure, and then the film was exposed outdoors in the same manner as in the same example, and various properties were measured on the film after outdoor exposure. did. The results are shown in Table 1. Comparative Example 4 Regarding a polyethylene terephthalate film (LLumar, thickness 125μ) whose surface was treated with an ultraviolet absorber and sold by Martin Processing Company, Inc. in the United States, as in Example 1, the film was before being exposed to the outdoors. Various properties were measured. Furthermore, the film was exposed outdoors in the same manner as in the same example, and various properties of the film after outdoor exposure were measured. The results are shown in Table 1. Comparative Example 5 A 2-( 2'-Hydroxy-5'-tertiary-butylphenyl)benzotriazole at 14% by weight based on resin solid content.
The UV absorber-containing film was coated using a gravure coating method and dried to form a film containing an ultraviolet absorber and having the same thickness as in Example 1. Regarding this film, various properties were measured in the same manner as in Example 1. The results are shown in Table 1. In addition, the film after the impact resistance test was exposed outdoors in the same manner as in Example 1, and various properties of the exposed film were evaluated in accordance with Example 1. It was measured. The results are shown in Table 2. Comparative Example 6 A film-formed film was obtained in the same manner as in Comparative Example 5, except that the thickness of the film formed on the base film was changed to 3.5 microns. Regarding this film, various properties were measured in the same manner as in Example 1. The results are shown in Table 1. In addition, the film after the impact resistance test was exposed outdoors in the same manner as in Example 1, and various properties of the exposed film were evaluated in accordance with Example 1. It was measured. The results are shown in Table 2.

【table】

【table】

[Table] From Tables 1 and 2, the following becomes clear. (1) Even when the agricultural polyethylene terephthalate film according to the present invention is exposed outdoors, it is hardly affected by ultraviolet rays, and there is little decrease in elongation rate or impact strength. On the other hand, in the film formed by adding an ultraviolet absorber (Comparative Example 3) and in the film in which the ultraviolet absorber was tightly bonded to the film surface (Comparative Example 4), the impact strength decreased significantly. (2) Even when the agricultural polyethylene terephthalate film according to the present invention is exposed outdoors, it does not cause small cracks on the surface, does not turn white, does not turn yellow overall, and is transparent. There is almost no difference in gender. On the other hand, in the case where no ultraviolet absorber was blended (Comparative Example 1), fine cracks were formed on the surface, the surface turned white, the entire surface turned yellow, and the transparency was significantly reduced. In Comparative Examples 2 to 4, fine cracks and whitening occurred on the surface, although the extent was not as great as in Comparative Example 1, and the transparency was considerably reduced. (3) The film formed on one side of the agricultural polyethylene terephthalate according to the present invention has excellent impact resistance, and even if an impact stress is applied to the film, cracks are unlikely to occur, and the film is difficult to peel off. On the other hand, when the film does not contain a cross-linked elastic body (Comparative Examples 5 and 6), it shows excellent weather resistance if no cracks occur in the film, but when subjected to impact stress, Cracks are likely to occur in the film, and once cracks occur, the film peels off, reducing mechanical properties and transparency.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an example of the agricultural polyethylene terephthalate film according to the present invention, and FIG. 2 is a cross-sectional view of the film according to the present invention when sunlight hits the film from the side where the acrylic resin film is provided.
Figure 3 is a diagram schematically showing the transmission of ultraviolet rays when sunlight is applied to a conventional polyethylene terephthalate film in which an ultraviolet absorber is uniformly dispersed throughout the film.
FIG. 4 is a perspective view showing a situation in which the impact resistance of a film formed on an agricultural polyethylene terephthalate film is tested. In the figure, 1 and 21 are polyethylene terephthalate films, 2 and 22 are acrylic resin films containing an ultraviolet absorber, 31 is a polyethylene terephthalate film containing an ultraviolet absorber, 41 is a blower, 42 is a wind tunnel, and 43 is a film, respectively.

Claims (1)

[Claims] 1 Stretched 2.0 to 5.0 times in each of the two axial directions
An agricultural polyethylene terephthalate film of 0.01 to 0.3 mm is formed on one side with a 1 to 10 micron thick acrylic resin film containing an ultraviolet absorber; (a) This acrylic resin is In the presence of crosslinked acrylic ester elastomer particles, a mixture of a methacrylic acid alkyl ester monomer or a methacrylic acid alkyl ester monomer as a main component and a vinyl compound monomer copolymerizable with this is polymerized. (b) The ratio of the crosslinked acrylic ester elastomer in the acrylic resin is 5 to 80% by weight. (c) The amount of ultraviolet absorber blended with acrylic resin
An agricultural polyethylene terephthalate film characterized in that the amount is 10 to 25 parts by weight per 100 parts by weight.