Implementing eco-friendly creaming agents to address coagulation issues and minimize acid consumption in skim natural rubber latex processing

• Published in: Industrial crops and products 2024-12, Vol.222, p.119499, Article 119499
• Main Authors: Kaesaman, Azizon, Kaewchuen, Sunida, Nakason, Charoen
• Format: Article
• Language: English
• Subjects: Creaming agent; Hydroxyethyl cellulose (HEC); Natural rubber; Skim latex; Tamarind kernel powder (TKP)
• ISSN: 0926-6690
• DOI: 10.1016/j.indcrop.2024.119499

The primary objective of solving problems related to skim latex coagulation and its subsequent uncoagulation with acid during long-term storage has been addressed through the application of creaming agents based on natural sources, namely tamarind kernel powder (TKP) and hydroxyethyl cellulose (HEC). The resulted creamed latex, where most rubber particles are covered with creaming agent molecules, was hypothesized to enable coagulation using dilute acid rather than the concentrated acid typically employed in the latex industry. This approach may also resolve the problem of uncoagulated long-storage skim latex, which results from anion formation. Creaming agents were firstly prepared at optimal concentrations of 2.0 wt% (HEC) and 3.0 wt% (TKP), and their molecular characteristics were analyzed using infrared spectroscopy. Various loadings of creaming agents (1.0–14 wt%) were then thoroughly mixed with skim latexes and conditioned at room temperature for 1–4 days to achieve complete separation. The resulting creamed latex was coagulated using 10 wt% concentrated sulfuric acid after the serum layer was separated out. Different properties of the dry skim rubber were characterized through various tests, including Mooney viscosity, plasticity retention index (PRI), dirt content, ash content, nitrogen content, and curing and mechanical properties. It was observed that the optimal concentrations of the creaming agents for preparing creamed concentrate skim lattices were determined to be 7.0 wt% with TKP and 12.0 % with HEC. In addition, only about half or one-third of the dilute acid quantity was required to coagulate the skim creamed HEC and TKP latexes compared with untreated skim latex. Furthermore, skim rubber derived from HEC and TKP creaming agents exhibited typical characteristics within the range of qualities of industrial skim rubbers available in the local rubber market, including Mooney viscosity (in the range 61–82), original plasticity (Po), PRI, curing, and mechanical properties (tensile strength, elongation at break and hardness). [Display omitted] •Two natural creaming agents were used to concentrate skim latex, separate it from serum, and coagulate it into skim rubber.•After creaming, dilute sulfuric acid coagulated the latex faster, reducing coagulation time and acidic effluent.•Creaming helps prevent uncoagulation in long-stored skim latex.•The skim rubber from creamed latex has qualities suitable for industrial use.