Effect of unmodified kraft lignin concentration on the emulsion and miniemulsion copolymerization of styrene with n‐butyl acrylate and methacrylic acid to produce polymer hybrid latex

Abstract

The introduction of non-modified kraft LignoBoost® lignin (KL) to produce polymer hybrid latex has received much attention in recent years because it is derived from renewable resources. The focus of this work is to develop a polymer hybrid latex by emulsion and miniemulsion copolymerization of styrene with n-butyl acrylate and methacrylic acid in the presence of different concentrations of KL furnished by the pulp and paper industry. The study intends to substitute a styrene in the system to understand the effect of non-modified KL on the properties not only of the latexes, but also on the copolymers themselves. Each polymerization was carried out by shot-process of tertbutyl hydroperoxide and sodium formaldehyde sulfoxylate as the redox system. The polymer latexes were characterized in relation to overall conversion, particle diameter, particle morphology, coagulum formation, surface tension, zeta potential, and atomic force microscopy.The polymers were evaluated through gel permeation chromatography, water absorption, and thermal properties. The results show that the addition of non-modified KL results in inhibition of the polymerization and that KL acts as a colloid stabilizer. Small particles were generated in the initial stages of the polymerizations. The presence of the KL altered the color of the latexes; the increase in KL concentration resulted in increase in the absorption of water of the polymer films; the increase in KL concentration resulted in decrease of the molar mass of the copolymers.

Emulsion Copolymerization of Styrene With n‐Butyl Acrylate and Methacrylic Acid: Effect of Kraft Lignin Concentration and Peroxide Treatment on the Colloidal Properties

“…In the peroxide treatment of KL under alkaline conditions, new functional compounds also can be formed, like carboxylate groups . However, the KL can also act as a stabilizer reducing the particle diameter and increasing the polydispersity …”

“…Solids content and overall conversion was measured by means of gravimetric analysis. The samples were put in pre‐weighed aluminum pans and dried in an air‐circulating drying oven for 2 h at 140 °C . The concentration of coagulum present in the latex was determined by isolating the coagulum using a stainless‐steel screen (125 µm) and then dried in an air‐circulating drying oven for 2 h at 140 °C.…”

“…The molecular weight and D values were derived from a calibration curve based on narrow polystyrene standards. Differential scanning calorimetry was run on a TA Instruments, Q200 after polymer purification . Samples of approximately 8–10 mg were enclosed in an aluminum pan and heated from 30 to 120 °C and cooled to 30 °C, and again heated to 200 °C with heating and cooling at 10 °C min −1 , under nitrogen atmosphere.…”

“…KL obtained from the black liquor in the pulping process differs from native lignin substantially in monomer composition, molar mass, reactivity, and solubility in water and in common solvents . Furthermore, low reactivity, insolubility in water and the presence of aliphatic thiol groups are a major limitation for industrial processing and large‐scale applications, especially to produce hybrid polymer . In this sense, to utilize KL with high efficiency, developing new methods to treat KL is encouraged to increase the reactivity.…”

“…A number of investigations have been conducted on the incorporation of KL by polymerization of different monomers and initiators, in order to produce new products by free‐radical polymerization . Some authors reported that the lignin accelerates the polymerization rate due to the existence of phenolic groups and other authors reported that the lignin inhibits the polymerization of vinyl monomers due the macromolecular structure of lignin . According to Jacob et al the selection of initiator and catalyst systems for graft copolymerization reactions is critical, especially in aqueous medium.…”