A versatile plastic for glasses

10 April 2018

Lens manufacturer Jiangsu Sigo Optical relies on polycarbonate from Covestro

Polycarbonate is an ideal lens material for corrective eyeglasses and sunglasses: It is lightweight, impact resistant, durable and comfortable. However, not all polycarbonate for eyewear applications is created equal. Covestro has developed special lens-quality grades of its Makrolon® polycarbonate which are characterized by excellent optical properties, high mechanical strength, toughness and comfort.
When original equipment manufacturer Jiangsu Sigo Optical Co., Ltd. (“Jiangsu Sigo Optical”) decided to upgrade the polycarbonate material used for its corrective and sunglass lenses, it turned to Covestro Makrolon® polycarbonate resins for improved optical purity and production yield.

High optical purity grade

For corrective lenses, Jiangsu Sigo Optical utilizes Makrolon® DP1-1821 polycarbonate, which is formulated specifically for the ophthalmic market. Available in clear tints, the material offers a number of advantages for corrective lenses including high optical purity, transmission and scatter resistance and UV stabilization. In processing, the material is distinguished by its high viscosity and easy release from the mold.
For outdoor activities, sunglasses provide UV protection, impact-resistance and style. Makrolon® LQ2887 polycarbonate, a new optical grade, is used for high-performance sunglass lenses from Jiangsu Sigo Optical. The abbreviation “LQ” stands for “lens quality”.

UV protection included

Importantly, Makrolon® LQ2887 polycarbonate provides UV protection from wavelengths up to 400 nanometers (nm), which blocks both energy-rich UVA and UVB rays. The product offers thin and fashionable, yet impact resistant lenses, and is appropriate for outdoor sports such as mountain biking and beach volleyball. UV protection is especially effective in beach and snow environments where water and snow strongly reflect harmful UV rays.
Owing to its medium viscosity and easy release from the mold, the product is easy to process. In addition to supplying the materials, Covestro also offers valuable technical assistance.

Rapid scale-up of a new product

“Our ophthalmic lens branded as Sigo+ meets the global market’s quality requirements with stable growth in export sales, thanks to the high productivity and low impurity quality of Makrolon® polycarbonate from Covestro,” explains Liu Jianzhong, General Manager, Jiangsu Sigo Optical Co., Ltd. “The project team had Covestro’s full support, which helped them scale up the new material on production lines just in three months.”
The successful product launch was also noted by Marina Lee, Senior Marketing Manager, Medical and Consumer Products – Polycarbonates, Asia Pacific, Covestro (Shanghai) Management Co., Ltd. “We worked closely with Jiangsu Sigo Optical and provided on-site technical support to ensure the process of qualifying the high-quality Covestro materials went smoothly. As a result, the use of Makrolon® LQ2887 polycarbonate in the sunglass lenses provides outstanding UV performance with protection to 400 nanometers,” she explained.

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