Preparation of UV protection products
Preparation of UV protection products
4.1 UV protection properties of ordinary fibers
Select cotton, wool, silk, polyester, viscose and other woven fabrics that have not been dyed and have similar process parameters to test the UV transmittance. The results are shown in Table 1. It can be seen from Table 1 that different fiber fabrics have a great influence on the ultraviolet light transmittance. The ultraviolet light transmittance of wool fabric is low (8.6%) and that of viscose fabric is high (27.3%). It should be noted that the thickness of the wool fabric in the test was almost 2 times that of other fabrics, because wool fabrics with the same thickness as other sample fabrics were not found. Therefore, when conducting comparative analysis, the average UV transmittance needs to be corrected with thickness and coverage. Among the corrected average UV transmittances, the lower ones are silk fabrics and polyester fabrics (16.8% and 15.3%), while the UV transmittance of cotton fabric and viscose fabric is higher (26.9% and 26.0%).
Analysis of the reasons is mainly because protein fibers such as wool and silk contain aromatic amino acids, and polyester molecules contain benzene rings. Their molecular activity is relatively large, and they have good absorption of ultraviolet light less than 300 nm, and most polyester The fibers contain matting agents, which have high absorption rates for UVA (320~400 rim) and UVB (290~320 nm). Cotton fiber and viscose fiber lack this active group, so their ability to protect against UV radiation is low.
Hemp fibers have a unique pectic oblique pore structure; ramie and apocynum fibers have groove-like cavities in the middle and porous walls; hemp fibers have elongated cavities in the center and many longitudinally distributed holes on the fiber surface. Cracks are connected to small cavities. Due to these structural reasons, hemp fiber not only absorbs water well, but also has a good elimination effect on sound waves and light waves, so it has strong UV protection function.
UV radiation blocking agents such as zinc oxide, titanium oxide, zirconium carbide, zirconium oxide or ceramic particles are mixed into the spinning solution (polyester, nylon, acetate fiber, acrylic fiber, etc.) to make anti-UV radiation fibers. The ultraviolet radiation transmittance of fabrics woven with this kind of UV-resistant polyester fiber is about 1/15 of cotton fabrics and 1/6 of ordinary polyester fabrics. Therefore, wool, linen, silk, polyester, UV-resistant chemical fiber, etc. with anti-UV function should be the first choice raw materials.
4.2 Production method of UV-resistant fiber
(1) Add components with ultraviolet shielding properties during the polymerization process of the fiber-forming polymer or in the molten state. Select a suitable ultraviolet absorber to copolymerize with the monomer of the fiber-forming polymer to obtain an anti-ultraviolet copolymer, and then spin it into anti-ultraviolet fiber. For example, Japanese patent reports use conventional direct esterification or transesterification followed by polycondensation to produce linear polyester with good UV protection, and then spin it into fibers through conventional melt spinning. This fiber has good anti-ultraviolet properties and can effectively absorb ultraviolet rays with a wavelength of 280 to 340 nm, and can be used as outdoor products.
Use at least one aromatic dicarboxylic acid (such as TPA, IPA, etc.) and EG as raw materials, and add 0.04%-10% divalent phenol with a mass fraction of 0.04%-10% to the raw materials or the ethylene glycol of the dicarboxylic acid, which can withstand 250°C. Compounds (such as 4,4′-dihydroxybenzophenone, etc.) are used to prepare linear polyester with good UV protection by conventional direct esterification or transesterification polycondensation method, and then through conventional melt spinning method Spun into fiber. This fiber has good UV protection properties and can effectively absorb UV rays with a wavelength of 280-340nm.
(2) Mix ultraviolet shielding agent into the fiber during the fiber manufacturing process or at any stage. The production of anti-UV fiber can be made by blending and spinning, that is, the powder of UV shielding agent or UV absorber is added to the polymer during polymerization or directly blended and spun. It can also be made into anti-UV masterbatch and then spun. . The anti-UV fiber produced in this way has longer-lasting anti-UV function than textiles made by post-finishing methods, has good washability, soft hand feel and is easy to dye. However, the mixed spinning method has different functions due to the difference in the amount of powder added, the size and uniformity of the particles, and may gradually block the spinneret holes, shorten the life of the spinneret, and increase costs.
Anti-UV additive performance It is important to choose the right anti-UV additive. It needs to be able to selectively and strongly absorb ultraviolet rays with a wavelength of 290 to 400 nm, and effectively prevent and inhibit ultraviolet rays from penetrating. It should also have low volatility, good thermal stability, chemical stability, hydrolysis resistance, water extraction resistance, compatibility with polymers, etc. After the polymer is modified with additives, it can have good washing resistance and ironing resistance like ordinary products; good safety and light stability; no harm to the skin, and comfortable to wear in the sun.
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