Synthesis and Retanning Performance of a Novel Melamine Resin with Ultralow Formaldehyde Content

Diethanolamine, epichlorohydrin (ECH), and lysine were used to change the traditional synthesis route to address the formaldehyde emission issue of melamine resin (MR), and a novel waterborne MR retanning agent with ultralow formaldehyde content (MUF) was finally obtained. The structure of MUF was characterized by Fourier transform infrared spectroscopy, 13C nuclear magnetic resonance, and X-ray photoelectron spectroscopy, and its retanning performances in wet-blue and wet-white leathers were thoroughly investigated. Results showed that the formaldehyde content of MUF was 28.05 mg/kg, which was greatly lower than that of traditional MR (3550.23/2543.45 mg/kg), and the formaldehyde contents of chrome- and TWLZ-tanned leathers retanned by MUF were only 12.68 and 8.98 mg/kg, respectively. The thickening rates of MUF-retanned leather were up to 13.40% (chrome-tanned leather) and 9.58% (TWLZ-tanned leather), and MUF showed a satisfying overall performance in retanning leather. MUF is highly promising in practical application owing to its ultralow formaldehyde content, excellent stability in aqueous solution, and satisfactory retanning behaviors.