Deproteinised Natural Rubber (DPNR)

Deproteinised Natural Rubber (DPNR) is a purified form of natural rubber (NR) from which most of the ash and protein components have been removed. The rubber is produced under very closely controlled conditions at the Rubber Research Institute Experimental Station, Sungai Buloh, Selangor, Malaysia. It contains about 96% rubber hydrocarbons compared to about 93% for normal natural rubber grades. The removal of these non-rubber components confers special attributes to the rubber which enhance its value in certain specialized applications.

DPNR CV Production Process

DPNR is prepared by treating field latex with a proteinase to hydrolyse the proteins in the latex which are then washed away during processing. Ammonia, a non-ionic surfactant, a proteinase and hydroxylamine Neutral Sulphate (HNS) are added into bulked field latex and allowed to react for 72 hours in a stainless steel conical bottom reaction tank. After the completion of the enzymatic hydrolysis reaction, the reacted latex is neutralized with dilute formic acid and coagulated by steam in a specially designed steam column coagulator. The resultant coagula are then processed in a continuous fashion through a series of crepers and finally chopped into small crumbs in a shredder. The crumbs are pumped through a static screen before entering the dryer boxes. The wet crumbs are then dried at about 85oC for about 6 - 8 hours in a hot air dryer. After cooling the crumbs are weighed, pressed, baled and packed to SMR standards.

DPNR – Grades

Two principal grades of DPNR are available. They are:

• DPNR CV – Viscosity stabilised at between 60 – 70 Mooney units.
• DPNR S – No viscosity stabilisation feature. The initial viscosity is between 70 – 80 Mooney units. Owing to the education on non-rubber content, the DPNR S has a very much less storage hardening than the normal NR.

Characteristics Of DPNR

• Very low protein content
  
• Very low dirt and ash contents
  
• Low volatile matter content
  
• Light colour
  
• Negligible nitrosamines
  
• Very low antigen content

Specifications Property DPNR CV DPNR S Dirt retained on 44 aperture sieve (% wt max) 0.01 0.01 Ash content (% wt max) 0.15 0.15 Nitrogen content (% wt max) 0.12 0.12 Volatile Matter content (% wt max) 0.30 0.30 Mooney viscosity [ML(1+4)@100ºC] 60-70 - AP(Max) 8 - Wallace Plasticity (min - 35 These raw rubber characteristics are reflected in the following valuable attributes of DPNR vulcanisates particularly when compounded using soluble vulcanising systems. Lower creep and stress relaxation Lower water absorption Greater consistency in modulus under conditions of variable humidity Area of Application Features Applications Low stress relaxation & creep Seals, Joint rings, Hydro-mounts Low water absorption Undersea applications Good dynamic properties Anti-vibration mountings Low protein Medical and food applications Packaging The standard packaging for DPNR is in 1.2 metric tonne wooden crates with the following specifications:- No. of bales per crate 36 Bale weight (kg) 33.3±0.5 Bale nominal dimensions 330 x 670 x 170 mm Bale wrapper Thickness: 0.03-0.05 mm Density: 0.92 g/cc Melt point: 109ºC Compatible with rubber @ 110ºC min Other forms of packaging/wrapping can be provided on request