JPS6236055B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a weather-resistant polyester sheet, and more specifically to a method for producing a polyester sheet with excellent weather resistance by effectively and economically tightly bonding an ultraviolet absorber to a polyester sheet. 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 disadvantage 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 sheets, methods are known, such as melt-blending an ultraviolet absorber with polyester before molding, and coating the surface of a molded sheet with a binder to form a coating film. However, the former method is not only uneconomical because the UV absorber is uniformly distributed throughout the sheet and requires a large amount of UV absorber to be blended, but also causes heat 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. easy to do,
It has drawbacks such as causing discoloration and decreased 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 provides a polyester sheet with an ultraviolet absorber that has an affinity for the sheet, and then a sheet that has no or poor affinity for the ultraviolet rays and does not transmit the ultraviolet absorber. It is characterized by polymerization and heat treatment.

When the method of the present invention is used, even the ultraviolet absorbent having sublimation property is temporarily separated from the outside air by the opaque sheet and heat-treated, so that the heat can be effectively diffused into the surface layer of the polyester sheet and treated. Because thermal deterioration of the agent can be prevented, the amount used can be reduced and excellent weather resistance can be obtained. Furthermore, it is economically advantageous that a relatively large amount of the oxide can be 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. The polyester sheet obtained according to the present invention can exhibit particularly excellent effects when used as an outdoor spreading material such as a car body cover material, an agricultural material, a balloon 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
A polymer blend of polyethylene terephthalate and a copolymerized polyester, a polymer blend of 85% by weight or more of polyethylene terephthalate and/or the above-mentioned copolymerized polyester, and 15% by weight or less of other polymers, etc., such that the sheet is Examples include films, tapes, fabrics, nonwoven sheets, synthetic papers, and composite sheets made of the above sheet and other sheets.

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
may be the same as or different from R ₃ ).

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, R ₂ is a hydrogen atom, a halogen atom, an alkoxy group, an alkyl group, etc., and 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 UV absorber is usually added to an organic solvent such as alcohols, ketones, aliphatic hydrocarbons, aromatic hydrocarbons, esters, and cyclic ethers with a boiling point of 120℃ or less. After the polyester sheet is immersed in a solution dissolved in an organic solvent having the following properties, it is optionally dried in a mangle hot air dryer. In addition, water dispersion system,
It can also be used in a mixed water-organic solvent system. In addition to the above-mentioned dipping method, the coating method can also be applied by a coating method, a spray method, a liquid transfer method, a coating method, or the like. This application method is advantageous when applying only to one desired side. In particular, in treatment solutions where the solvent is aqueous, in order to improve uniform adhesion and reproducibility of effects, polymeric thickeners that have no or poor affinity for ultraviolet absorbers, such as alginate propylene glycol ester, hydroxypropyl cellulose, etc. Alginic acid, methylcellulose, polyvinyl alcohol, etc. can be added. Of course, it is selected from polymers that dissolve in the solvent used.
Drying is usually done to suppress the volatilization of the ultraviolet absorber.
It is carried out at a temperature of 120°C or lower, preferably 80 to 100°C. After drying, at least the surface to which the ultraviolet absorber is applied is laminated with a sheet that has no or poor affinity for the ultraviolet absorber and does not transmit the ultraviolet absorber, and is heated at a temperature above the drying temperature and below the melting point of the polyester. Heat treatment is carried out at a temperature range of 120 to 200°C, usually within 60 minutes, preferably from several seconds to several minutes.

The sheet that does not transmit the ultraviolet absorber is a sheet that does not transmit the vaporized ultraviolet absorber, and paper is the most economical sheet. Air permeability is 100 for paper
It is necessary that the air permeability is less than cc/cm ² ·sec. In particular, paper that has been packed by calendering or the like has essentially zero air permeability and is extremely effective. Paper processed with silicone resin, fluororesin, etc. is also effective. In addition to paper, heat-resistant, flexible sheets coated with silicone resin, fluororesin, etc. are also effective. Further, in the heat treatment step, the running polyester sheet and the endless belt made of the sheet having the above performance may be polymerized and heat treated.

Note that the affinity of the sheet for the ultraviolet absorber is determined by the following method. That is, the ultraviolet absorber is dissolved in an organic solvent, applied onto a sheet of known weight, the solvent is evaporated, and the weight of the ultraviolet absorber on the sheet is measured. This sheet was then heated at 140℃.
After heating for 60 minutes, the weight is weighed again, and if the amount of ultraviolet absorber before heating decreases by 70% or more, affinity is determined to be poor or absent.

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

Example 1 Substituted benzophenone ultraviolet absorber Cyasorb
A polyethylene terephthalate film (1.5 mm thick) was immersed in a 10% methyl ethyl ketone solution of D-24 (Japan Cyanamid Co., Ltd.) for 3 seconds at 25°C.
Lightly squeezed to a wet pick-up ratio of 15% and dried. The dried film was then sandwiched between commercially available gravure papers (air permeability: 0 c.c./cm ² ·sec, thickness: 0.3 mm) and heat-treated at 180° C. for 10 seconds. On the other hand, as Comparative Example 1, the temperature was raised to 180℃ without using paper.
Heat treated for 10 seconds.

Example 2 Substituted benzophenone ultraviolet absorber Uvinol D
A polyethylene terephthalate film (1.5 mm thick) was immersed in a 10% isopropanol solution of -49 (G.A.F. Co., Ltd.) at 25°C for 3 seconds, and then taken out vertically from the liquid surface (wet pick-up rate
10%) and immediately dried at 100°C. The dried film was then sandwiched between calendered gravure papers and heat-treated at 170°C for 15 seconds. On the other hand, as Comparative Example 2, the paper was heat-treated in a hot air dryer at 170° C. for 15 seconds without using paper.

As a result of measuring the ultraviolet absorption spectrum of the polyester films obtained in Examples 1 and 2 using a spectrophotometer (manufactured by Hitachi, Ltd.), it was found that all wavelengths of 370 mμ or less were blocked. Further, in order to evaluate weather resistance, the films treated in Examples 1 and 2 were exposed for 2000 hours using a weather-o-meter, and the retention of tensile strength was 90% or more, and the retention of elongation at break was 80% or more. On the other hand, after 1000 hours of exposure, the untreated film already has a tensile strength retention rate of 60% and a fracture elongation retention rate of 60%.
It had dropped to 30%.

Further, the treated fabrics of Comparative Examples 1 and 2 had a cut rate of only 10 to 20% at wavelengths of 370 mμ or less, as determined by measurement of ultraviolet absorption spectra.

Claims (1)

[Scope of Claims] 1. After adding an ultraviolet absorber that has an affinity for the sheet to a polyester sheet, a polyester sheet that has no affinity or a poor affinity for the ultraviolet absorber and that has no affinity for the ultraviolet absorber. A method for producing a weather-resistant polyester sheet, which comprises polymerizing and heat-treating a non-transparent sheet. 2. The method for producing a weather-resistant polyester sheet according to claim 1, wherein the ultraviolet absorber is an ultraviolet absorber that has sublimation properties at a temperature of 250° C. or less under atmospheric pressure.