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Polyester fibre coloring modifier is white crystal with melting point above 300 ℃.

Used as polyester dye modifier. It can improve the defects of poor dyeing and poor hygroscopicity of polyester fibers, and obtain high-quality fibers with bright color, good hygroscopicity and high wet fastness.

Add 80 kg of isophthalic acid into the reaction kettle, then add 45 kg of liquid SO₃, stir and heat up to 166 °C, react for 0.5 h, then continue to heat up to about 180 °C, and react for 6 h to obtain isophthalic dicarboxybenzene sulfonic acid. After cooling, add methanol (the mass of methanol is about 1/3 of isophthalic acid), add 1/3 methanol first, keep the temperature at about 130 °C during the dropwise addition, and then cool to about 60 °C and add the remaining 2/3 methanol . After the addition, the mixture was stirred for 2 h, cooled, neutralized with Na₂CO₃, filtered and dried.
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