PARLIAMENTARY STANDING COMMITTE - COMMERCE HASD A SITTING IN KOCHI ON 9 JANUARY 2020

The following details outling the present situation relating to 60% Latex was submitted to the Committee: 

NATURAL RUBBER LATEX

 A PROFILE ON LATEX INDUSTRY IN INDIA

 By THE ASSOCIATION OF LATEX PRODUCERS OF INDIA KOTTAYAM, KEARLA.  

January 2020

SHORT NOTE ON 60% NATURAL RUBBER CENTRIFUGED LATEX

INTRODUCTION

Among the different marketable forms of natural rubber, latex concentrates are the most value-added form that can be produced from raw field Latex from the large as well as small rubber growers. For the organized processing and marketing of field Latex produced by small rubber holders, processing into centrifuged latex concentrates is considered as ideal and the best on account of the fact that it is relatively less labor intensive.

The total installed capacity for processing into centrifuged latex concentrates in India currently comes to 2,50,000 tonnes in terms of DRC. However, constrained by wide fluctuations in demand and prices, the current level of capacity utilization is less than 50% only.

Latex Preservation and Concentration

Latex Properties

Latex is a white or slightly yellowish opaque liquid with a specific gravity, which varies between 0.974 and 0.986. It is a weak lyophilic colloidal system of spherical or pear shaped rubber globules suspended in an aqueous serum. The rubber globule is surrounded by a protective layer of proteins and phospholipids, which impart the lyophilic nature to latex.

The stability of latex is due to the negative charge present on the protective layer. Also it contains a variety of non-rubber constituents both organic and inorganic, in addition to rubber. The proportion of these constituents may vary with clone, soil nutrition, climate etc.

General composition of latex

Fresh latex, as it comes out from the tree is slightly alkaline or neutral. It becomes acidic rapidly due to bacterial action. The formation of organic acids neutralizes the negative charge on rubber particles and the latex gradually gets coagulated on keeping. Therefore, fresh latex cannot be kept for long without preservative treatment.

Latex can be processed into any of the following forms

1. Preserved field latex and latex concentrate
2. Sheet rubber
3. Block rubber
4. Crepe rubber

Field coagulum can be processed only into crepe rubber or block rubber.

Preserved field latex

Field latex is preserved using suitable preservative for long term storage. The processing of preserved field latex consists essentially of adding the preservative (usually ammonia, minimum 1%) to the sieved latex, bulking, settling, blending replique montre suisse and packing. Field latex can also be preserved with LATZ (Low ammonia – TMTD – Zinc oxide) system.

Latex Concentrate

There is good market for preserved latex concentrate, as it is an important raw material with a wide range of applications. Two important methods of processing latex into preserved latex concentrate are commercially practiced.

1. Concentration by Creaming

The processing of latex into creamed concentrate involves the mixing of a creaming agent such as ammonium alginate or tamarind seed powder with properly preserved field latex and allowing the latex to separate into two layers; an upper layer of concentrated latex and a lower layer of serum containing very little rubber. The lower layer of serum is removed, leaving the latex concentrate having about 50-55% DRC (dry rubber content), which is often tested, packed and marketed.

2. Concentration by Centrifugation

The processing of latex into latex concentrate by centrifugation involves the separation of preserved field latex into two fractions, one containing the concentrated latex of more than 60% dry rubber and the other containing 4-8% dry rubber (skim latex).
Skim latex is generally coagulated with sulphuric acid, made into crepe, dried and marketed as skim rubber, which is a low-grade rubber.

Preservation of Centrifuged Latex

Centrifuged latices are commercially available as high ammonia (HA – minimum 0.6% ammonia) and low ammonia (LA - 0.2 to 0.3% ammonia) types. The former is preserved solely with ammonia and the latter contains one or more preservatives in addition to ammonia. The most popular LA type latex is low ammonia TMTD – Zinc oxide (LA-TZ) which contains 0.2 to 0.3% ammonia, 0.013% TMTD, 0.013% zinc oxide and 0.05% lauric acid.

Specifications

Preserved latex concentrates shall be graded and marketed in conformity with the standards specified by the Bureau of Indian Standards (BIS) as given in IS: 5430-2017 (centrifuged latex), IS: 11001-1984 (double centrifuged latex) and IS 13101-1991 (creamed latex).

IS 5430 : 2017

Table 1:   Requirements for Concentrated and Preserved Natural Rubber Latices

(Clause 4.3)

1)  Difference between total solids content and dry rubber content. Total solids contents may be determined in accordance with 9316 (Part 4)ysl imitacion
2) Test for mechanical stability shall be carried out at least 20 days of the packing of rubber latex
3) Or as agreed to between the purchaser and the supplier

Product Features

Centrifuged Latex of 60% of Dry Rubber Content (CENEX)

Processing of natural rubber latex into high quality latex concentrate of 60% dry rubber content is done through centrifugation. Centrifuging involves the separation of preserved field latex into two fractions, one containing the concentrated latex of more than 60% dry rubber and the other containing 4-6% dry rubber.  Centrifuged latex is today available commercially in two different verities with high ammonia (min.0.7% of ammonia) and low ammonia (max. 0.3% of ammonia). The former is preserved solely with ammonia and later contains one or more preservatives besides ammonia. LA latex has several advantages which include better quality, lower cost of production by way of savings in preservatives, acid and low cost of effluent tre