Difference between revisions of "Gutta percha (FAO, NWFP 6)"

Revision as of 19:40, 8 July 2020

• Extract from : NWFP 6. Coppen J.J.W., 1995. Gums, resins and latexes of plant origin. FAO, Rome. 142 p. (Non-Wood Forest Products, 6). on line

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DESCRIPTION AND USES

Gutta percha is the coagulum produced from the latex of certain trees of the Sapotaceae family indigenous to Southeast Asia, particularly those found in the Malay and Indonesian archipelagos.

In contrast to rubber, which is an elastic material, gutta percha is non-elastic; it becomes plastic when heated but retains its shape when cooled. The differences between the two materials arise from their different chemical compositions: rubber and gutta percha both contain a large proportion of the polymeric hydrocarbon polyisoprene, but in the former it is the cis isomer while in the latter it is the trans isomer. The presence of trans polyisoprene in balata-like materials originating from tropical America is referred to elsewhere (BALATA and [[Maçaranduba (FAO, NWFP 6)|MAÇARANDUBA), and confers on them their non-elastic properties.

Towards the middle of the last century it was discovered that gutta percha had excellent insulating properties which were retained under water, and its most important use was in providing the insulating material for submarine and underground cables. It was also used (as was balata) for the manufacture of golf ball covers and other moulded products. However, the advent of synthetic resins and other, petroleum-based polymeric materials led to the rapid decline in use of the natural material.

WORLD SUPPLY AND DEMAND TRENDS

Markets

Average annual world consumption of gutta percha in the early part of the century (40 years up to 1936) has been stated to be approximately 850 tonnes, of which about 450 tormes were used for submarine cables, 300-400 tonnes for the manufacture of golf balls, and the remainder for miscellaneous industries such as machine belting (READER, 1953). LOCKHART-SMITH (1972), on the other hand, states that exports of gutta percha and inferior guttas from Singapore averaged nearly 14 000 tonnes annually between 1900 and 1920. By the 1960s/1970s, golf ball manufacture was the only significant end use for gutta percha (and balata).

In the 1960s, the United States was by far the largest importer of gutta percha; average annual imports from Indonesia over the 10 years 1963-72 were 1 140 tonnes (LOCKHARTSMITH, 1972). Recent US data are not available. It is not easy to draw conclusions about present day consumption of gutta percha on the basis of trade statistics alone. Gutta percha is not always disaggregated from other non-elastic gums, and although an attempt has been made to do this in the case of recent imports into Japan of "chicle, balata, gutta percha and guayule" (Table 32), the average annual figure of about 970 tonnes for assumed gutta percha imported from Indonesia is much greater than total recorded exports of gutta percha out of Indonesia for the same period (Table 35, annual average 190 tonnes). Furthermore, of these total exports, only 6 tonnes (in 1993) went directly to Japan.

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Supply sources

In past years, Indonesia and Malaysia have been the dominant producers of gutta percha, with minor quantities coming from Thailand and a few other countries in the region. Singapore is often the first destination for exports, which are then re-exported to end-user countries.

Indonesia is believed to be the largest producer and exporter of gutta percha today, although it is not clear whether the quantities given in Table 35 are a true reflection of the size of this trade.

Quality and prices

The quality of gutta percha, both in its crude and processed form, depends largely on its hydocarbon (gutta) content, since it is this that confers on gutta percha its thermo-plastic properties. Most of the remaining material is "resin". Gutta percha which has been extracted from leaves by non-solvent methods (see VALUE-ADDED PROCESSING below) contains around 70-75% hydrocarbon and 6-10% resin; the balance is moisture and a few per cent of solid impurities. Fully refined, solvent-extracted gutta percha ("white gutta") contains less than 1% resin.

FOB export values for gutta percha of Indonesian origin have been quite steady for the last three years of data (1991-93): approximately US$ 1 200/tonne. In 1990 it was about US$ 1 900/tonne.

PLANT SOURCES

Botanical names

Family Sapotaceae:

• Palaquium gutta (Hk. f.) Baillon

Other Palaquium spp., including Palaquium obovatum (Griffith) Engler, Palaquium oblongifolium, Palaquium oxleyanum Pierre and Palaquium treubii.

• Payena leerii (Teys. et Binn.) Kurz

Description and distribution

Palaquium species are medium to very tall trees. Palaquium gutta is a medium tree, up to 25 m in height and 1.5 m in girth, with small buttresses. Payena leerii grows up to 40 m high.

The main gutta percha-yielding trees are found in Indonesia and Malaysia, particularly the islands of Sumatra and Borneo and smaller surrounding ones. However, they occur as far north as the Philippines and mainland Southeast Asia, and as far east as Papua New Guinea.

Palaquium species are amenable to cultivation and plantations were established in Java for gutta percha production as early as the 1890s. Commercial plantations were also being worked in Malaysia in the 1950s, but the last of these ceased operation in 1967. LOCKHART-SMITH (1972) reported that the plantation at Cipetir, West Java, was the only active one in the early 1970s; its status today is not known. Although Palaquium gutta produces the highest quality gutta percha, Palaquium oblongifolium is the species most suited to planting.

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COLLECTION/PRIMARY PROCESSING

In the early 1900s, when demand for gutta percha was at its greatest, collection of the latex from wild trees was entirely by destructive means, so as to obtain as much as possible: the tree was felled, the branches lopped off, and a number of wide cuts made through the bark at intervals along the trunk. When it became clear that this was leading to significant losses of forest, such methods were banned and techniques for tapping the living tree were developed.

Usually these methods entailed making a series of V-shaped cuts in the bark of the tree about 20-30 cm apart, with a central, vertical channel. Most of the latex coagulated in the cuts and was collected by rolling it into small balls along the cuts; the remainder flowed into small cups fixed to the tree. A rest period of at least two years was said to be necessary between successive tappings to keep the tree economically productive. Unlike rubber trees, which contain laticiferous tubes in the bark, Palaquium spp contain irregular cavities which are not connected, and tapping cannot be done in a manner similar to that for rubber.

In plantations, extraction of gutta percha from the leaves of the trees is more productive than collection of latex by tapping. Harvesting is done partly by plucking (about four times a year) and partly by collecting prunings (which comprise leaves, twigs and small branches).

Primary processing of the latex entails pressing the partially formed coagulum into blocks after first softening it in hot water and removing larger pieces of foreign matter. The blocks are then transported to the factory for further processing; if they need to be stored for any length of time before transportation they are best kept under water to avoid spoilage by aerial oxidation.

Extraction of the gutta percha from leaves is briefly described under VALUE-ADDED PROCESSING, since some aspects of it are similar to methods used for further processing of the crude gutta percha blocks.

Yields

Tapping yields of latex depend on both genetic and environmental factors, as well as the part of the tree which is tapped. In Palaquium oblongifolium, for example, the latex hardens after a few minutes of exposure to the air, and the yield is considerably lower than that from Palaquium obovatum. Cloudy, moist conditions allow the latex to flow more easily than during hot, sunny periods, when there is some loss of water by evaporation. Higher yields are also obtained from the upper portion of the trunk and branches than from the lower part. Yields of gutta percha per tree are also very variable, but about 1.5 kg has been stated to be a good average.

The gutta percha content of leaves increases with the age of the leaf: results reported in the older literature state about 3% (dry basis) in young leaves, 8% in medium-aged leaves and 10% in old leaves.

VALUE-ADDED PROCESSING

Preparation of purified gutta percha involves chopping the blocks of crude material into small pieces, removing the resinous ("non-gutta") fraction by dissolution in cold petroleum spirit, and then dissolving the remaining, separated gutta fraction in hot petroleum spirit. This hot

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extract is drained from any insoluble foreign matter and then allowed to cool, whereupon the purified gutta percha separates out. After separation and distillation of residual solvent the hot, plasticized gutta is rolled into sheets and stored, either in the dark in well sealed tins, or in water.

Solvent extraction of gutta from harvested leaves follows the same principles as above, but involves pulverized leaf material instead of chopped crude gutta percha. Bleaching earth is added to the hot mixture to remove unwanted leaf pigments.

An alternative method of processing the leaves involves digesting the leaf pulp in hot water, and collecting and pressing the coagulated latex which separates out into blocks.

PRODUCTS OTHER THAN LATEX

No other products of economic value are believed to come from the gutta-yielding species.

DEVELOPMENTAL POTENTIAL

Although recent Indonesian export data show a modest upward trend, there is insufficient information, here, to be able to make an informed judgement as to the developmental potential of Palaquium and gutta percha production. In particular, it is not known whether the gutta percha produced in Indonesia (or elsewhere) comes from plantation or wild sources.

SELECTED BIBLIOGRAPHY

• LOCKHART-SMITH, C.J. (1972) Market prospects for gutta-percha. Report of the Tropical Products Institute, London [now Natural Resources Institute, Chatham].
• READER, D.E. (1953) Gutta-percha. Colonial Plant and Animal Products, 3(1), 33-45.
• SERIER, J.B. (1986) [Tree secretions] [includes balata and gutta percha] (in French). Bois et Forêts des Tropiques, (213), 33-39.
• STERN, H.J. (1939) Gutta percha and balata: purification in the factory. The Rubber Age, (Oct.), 245-249 and 258.
• TONGACAN, A.L. (1971) Gutta Percha. FPRI Technical Note No. 106. 2pp. Laguna, the Philippines: Forest Products Research and Industries Development Commission.
• WILLIAMS, L. (1962) Laticiferous plants of economic importance. II. Mexican chilte (Cnidoscolus): a source of gutta-like material. Economic Botany, 16, 53-70.

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Source: National statistics