Effect of Prepolymerization of Acrylic Acid Under High Gravity on the Properties of Acrylic Resin Retanning Agent

Abstract

The effects of prepolymerization of acrylic acid (AA) in rotating packed bed (RPB) on the molecular weight and molecular weight distribution of polyacrylic acid (PAA) were investigated. Results showed that, compared with conventional polymerization in stirred tank reactor (STR), the prepolymerization in RPB followed by polymerization in STR produced PAA with lower weight average molecular weight (Mw) and polydispersity index (PDI). The Mw of PAA decreased with increasing rotational speed of RPB from 800 rpm to 1400 rpm. Therefore, the use of RPB might be an effective strategy to control the molecular weight and molecular weight distribution of PAA. For exploring the value of this technology in preparing PAA retanning agent, PAAs were synthesized by using STR (STR-PAA, Mw=476,615 Dal, PDI=3.36) and RPB (RPB-PAA, Mw=193,386-288,321 Dal, PDI=1.55-1.86), and their performances in retanning were evaluated. Results showed that RPB-PAAs with low Mw had high absorptivity in wet blue and achieved a good filling property for leather because they could permeate into numerous microstructures of collagen fiber network. As for RPB-PAAs, high PDI led to a satisfactory selective filling property. The fullness, mechanical property, isoelectric point, and dyeability of leather were also affected by PAAs with different Mw and PDI. This work demonstrated the considerable influences of the molecular weight and molecular weight distribution of PAA on retanning property. A method to control these parameters was also presented.