JPS6331502B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a weather-resistant polyester film, and more specifically to a method for producing a polyester film with excellent weather resistance by effectively and economically tightly bonding an ultraviolet absorber to a polyester film. Relating to a method of manufacturing.

Polyester molded products have high crystallinity, high melting point, and many excellent physical properties such as heat resistance, chemical resistance, high strength, and high modulus of elasticity, so they are important as industrial materials. occupies a position. However, such polyester molded products also have the drawback of relatively rapid deterioration when exposed to the outside air, particularly sunlight, resulting in a decrease in strength and elongation and yellowing. In addition, colored products have the disadvantage that the color tone changes and fades.

Conventionally, in order to improve the weather resistance of polyester film, methods are known in which a UV absorber is melt-blended with polyester before molding, and a method in which it is applied together with a binder to the surface of a molded film to form a coating film. However, the former method is not only uneconomical because the UV absorber is uniformly distributed throughout the film and requires a large amount of UV absorber to be blended, but it also causes thermal deterioration and discoloration of the UV absorber. Targeted low-molecular-weight compounds have drawbacks such as sublimation, resulting in poor reproducibility of effects, and various problems such as contamination around the polymer discharge hole. In addition, the latter method provides better results in terms of UV absorption than the former, but the binder in the coating layer deteriorates during exposure to the outside air, causing it to peel off from the polyester sheet, fall off, or become transparent. It has disadvantages such as reduced performance. Furthermore, a method has been proposed in which the UV absorber is dissolved in a carrier and absorbed at high temperatures, but since the treatment is carried out in a high-temperature carrier solution, extreme care is required during work, and the used carrier may remain. It has disadvantages such as being easy to peel and causing discoloration and a decrease in heat resistance.

As a result of intensive research into a method for improving weather resistance that does not have the above-mentioned drawbacks, the present inventor has arrived at the method of the present invention. That is, the present invention is characterized in that an ultraviolet absorber is applied onto a running polyester film, and after drying if desired, the applied surface is overlapped with the same polyester film and heated at a temperature of 100°C or higher. .

When using the method of the present invention, the coated surface is temporarily isolated from the outside air by the same polyester film and heat treated, so that even ultraviolet absorbers with sublimation properties are effectively diffused inside the surface layer of the polyester film. It has the characteristics that excellent weather resistance can be obtained with a small amount of use because it can prevent thermal deterioration of the treatment agent. It is also effective and economically advantageous to have a relatively large amount of ultraviolet absorber present near the surface layer that is exposed to light. Furthermore, the uniformity and reproducibility of the effect are extremely good, and it is possible to effectively prevent the deterioration and discoloration of polyester caused by light and the deterioration and fading of colored polyester. Furthermore, the ultraviolet absorber can be transferred to the opposite surface of the polyester film by overlapping the ultraviolet absorber-applied side with the other side of the polyester film and heating it. At this time, effective transfer can also be achieved by treating the ultraviolet absorber-applied surface in advance with a treatment agent that inhibits the diffusivity of the ultraviolet absorber.

The polyester film obtained by the method of the present invention can exhibit particularly excellent effects as an outdoor spreading material such as an agricultural material, a balloon material, a solar heat collecting material, an all-weather stadium roofing material, and the like.

Polyester as used in the present invention refers to polyethylene terephthalate, copolyester containing at least 85 mol% of ethylene terephthalate repeating units,
At least 85 ethylene terephthalate repeat units
Polymer blends of polyethylene terephthalate and copolymerized polyester, such as polymer blends of polyethylene terephthalate and/or the above copolymerized polyester with 85% by weight or more and 15% by weight or less of other polymers, etc. A long film is used. Further, in some cases, a composite sheet consisting of this sheet and other sheets may also be used.

The polyester may contain a lubricant, an eraser, a coloring agent, a stabilizer, an antifungal agent, an antioxidant, a polymer type or non-sublimation type light fastener, a dyeability improver, a flame retardant, etc. as necessary. It's okay.

The ultraviolet absorber used in the present invention is particularly preferably a compound that sublimes under atmospheric pressure at a temperature of 250°C or lower, especially at a temperature of 130 to 220°C, and has an affinity for polyester, but at a temperature of 250°C or lower. Low-molecular-weight ultraviolet absorbers that melt in polyester, have an affinity for polyester, and can be thermally diffused are also effective; for example, benzotriazole represented by the formula [] (However, R ₁ is a hydrogen atom, a halogen atom, a nitro group, etc., R ₂ and R ₃ are a hydrogen atom, a halogen atom, an alkyl group, a hydroxyl group, an alkoxy group, etc., and R ₂
and R ₃ may be the same or different).

Substituted benzophenone represented by formula [] (However, R ₁ is a hydrogen atom, a halogen atom, a hydroxyl group, an amino group, an alkoxy group, an alkyl group, etc.; R ₂ is a hydrogen atom, a halogen atom, an alkoxy group, an alkyl group; R ₃ is an alkyl group, etc.).

Other examples include salicylic acid esters such as phenyl salicylate, cyanoacrylates such as ethyl-2-cyano-3,3'-diphenyl acrylate, and hindered amines, but are not limited to these. do not have. Furthermore, the substituent may have a polymerizable or reactive group such as an unsaturated bond group or an epoxy group.

The method of applying the ultraviolet absorber in the present invention is not particularly limited and may be carried out by any means, but in order to ensure uniform application, the ultraviolet absorber is dissolved or dispersed in a medium containing a binder and coated. It is convenient to give it as a gift. The binder to be used must be a resin that has no affinity for the ultraviolet absorber, that is, does not inhibit the migration of the ultraviolet absorber, and must also be a resin that becomes sticky when heated and does not adhere to the other side of the peeled film. Generally, a polymer having a melting point of 200°C or higher, particularly 250°C or higher is preferred. Specifically, cellulose ethers such as hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, ethylcellulose, and carboxymethylcellulose, sodium alginate or its derivatives, starch or its derivatives, gums such as gum arabic, gum tragacanth, and locus bean gum, gelatin, and polyvinyl. Alcohols are preferred. The binder can also be used in combination with a thermosetting resin such as a phenolic resin, an aminoplast resin, or an epoxy resin, or a thermoplastic resin such as cellulose acetate, polyvinyl acetate, or polyvinyl butyral.

To further explain the method of the present invention using drawings, FIG. 1 is a process explanatory diagram showing an example of the manufacturing method of the present invention. Here, the film coated with the viscous material 2, passed through the drying equipment 5, and passed through the heating roll is treated film A. The processed film A passes through the guide roll 8, the heating roll 6, the guide roll 9, and is heated again. The film until it passes through the roll 6 is referred to as processed film B.

A viscous material 2 consisting of an ultraviolet absorber and a binder is applied onto a heat-resistant endless belt 4 using a doctor knife 3 while an original film 1 of a long polyester film is fed, and is dried in a drying equipment 5.

Next, the coated side of the treated film A and the non-coated side of the treated film B are overlapped and passed between the heating roller 6 and the heat-resistant endless belt 4 to coat at least part of the ultraviolet absorber from the coated side to the opposite side. The weather-resistant polyester film 7 is manufactured by heat transfer and internal diffusion. The heating roll 6 may be provided on the back side of the endless belt depending on the case. Further, the surface of the heating roll 6 can be treated with a release agent if desired to prevent contamination with binder or the like. If transfer is not desired, it is preferable to pre-treat the surface of the polyester film opposite to the surface to which the ultraviolet absorber is applied with a mold release agent or a treatment agent that does not diffuse the ultraviolet absorber.

The above has described a manufacturing method using a heat-resistant endless belt, but there are other methods such as coating by ordinary coating, heating along a heating roll, and passing it through a heating oven while running along a roll. It's okay.

Furthermore, in the manufacturing method shown in FIG.
The treated film B, which has not yet been guided, is twisted by a guide roll and turned upside down, so that the coated surface of the treated film A and the coated surface of the treated film B are overlapped, that is, the surfaces to which the ultraviolet absorber is applied are overlapped. They can also be heated together and diffused internally.

Drying after applying the viscous material is usually preferably carried out at 80 to 120°C; if the temperature is too high, depending on the type of UV absorber, the UV absorber may escape during drying. In addition, the heating required for transfer, internal diffusion, etc. of the ultraviolet absorber is usually 100 to 250℃, preferably 150 to 220℃.
A temperature of from several seconds to several minutes, preferably from 10 to 30 seconds, is employed. However, the conditions are not limited to these.

According to the method of the present invention, no particular washing step is required after treatment, and it is not only economical but also characterized by extremely simple process operations.

The present invention will be explained below with reference to Examples. In addition,
The percentages in the examples are by weight.

Example 1 A viscous substance having the following formulation was prepared.

Cyasorb D-24 (Nippon Cyanamid Co., Ltd., substituted benzophenone type) 10% Hydroxypropylcellulose (Nippon Soda Co., Ltd.) 10% Isopropanol 80% The obtained viscous material was coated on a polyethylene terephthalate film (thickness 1.5 mm) using the method shown in Figure 1. Apply 15g/m ² by drying at 80℃.
Heat and pressure treatment was performed for seconds.

Example 2 A viscous substance having the following formulation was prepared.

Uvinul D-49 (GAF, substituted benzophenone) 10% Ethylene glycol 10% Datuku Algin NSPL (Kamogawa Kasei, sodium alginate) 3% Water 77% Polyethylene terephthalate film (thickness 1.5 mm) obtained by applying silicone release treatment to the resulting viscous material. ) was applied at a rate of 15 g/m ² by the method shown in Figure 1, dried at 100°C, and heated and pressurized at 180°C for 10 seconds.

The ultraviolet absorption spectrum of the polyester films obtained in Examples 1 and 2 was measured using a spectrophotometer (manufactured by Hitachi, Ltd.), and it was found that all wavelengths of 370 mμ or less were blocked. Further, in order to measure weather resistance, the ultraviolet absorbent treated surface was exposed for 2000 hours using a Weather-O-meter, but both Examples 1 and 2 showed almost no change. On the other hand, the untreated film showed a large decrease in strength (retention rate below 50%) after 1000 hours.

A miniature greenhouse was also made using the film obtained in Example 1 and the untreated film. That is, it was stretched side by side with an untreated film with the ultraviolet absorbent transfer surface facing outside. As a result, in the case of the untreated film, water vapor condensed on the inner surface especially in winter, causing the film surface to become cloudy, but in the treated film of Example 1, the hydrophilic film of the binder used on the back surface prevented clouding. It also had the effect of

[Brief explanation of the drawing]

FIG. 1 is a process explanatory diagram showing an example of the manufacturing method in the present invention. 1... Polyester film raw material, 2... Viscous, 3
...Doctor knife, 4...Heat-resistant endless belt, 5...
Drying equipment, 6... heating roller, 7... weather-resistant polyester film, 8... guide roller, 9... guide roller.

Claims (1)

[Claims] 1. Applying an ultraviolet absorber to a running long polyester film, drying if desired, and then overlapping the applied surface with the same polyester film and heating at a temperature of 100°C or higher. A method for producing a weather-resistant polyester film characterized by: 2. Production of a weather-resistant polyester film according to claim 1, in which an ultraviolet absorber is dissolved or dispersed in a medium containing a binder having a melting point of 200° C. or higher and having no affinity for the ultraviolet absorber. Method.