When he was in Haiti in 1493, Christopher Columbus noticed that the natives were bouncing on rubber balls made from the milky sap of Hevea brasiliensis, also known as a rubber tree native to South America. The milky sap was nothing but latex, the source material for natural rubber. Latex processing technology includes equipment for coagulation techniques and rollers for natural latex and a sequence of mixers, pumps, and sieves for synthetic latex.
Which latex equipment do you need?
Active freeze dryer
Laboratory scale active freeze dryer
Top loading arm
Bottom loading arm
Wiped film evaporator
Short path evaporators
Deduster for injection moulding
Small scale deduster for plastic granules
Tumble dryer for granulated plastics
Drum cooler for laboratory hot melt processes
Drum cooler for hot melt processes
High capacity drum cooler for hot melt extrusion
Steel belt cooler for hot melt extrusion
Laboratory GMP cooler for hot melt extrusion
GMP cooler for hot melt extrusion
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The three faces of the milky liquid
Latex is a milky liquid with a composition of 45% water and 55% rubber concentrated just beneath the mature rubber tree bark, found in South America and Southeast Asia. It is a resistant, flexible, nonabrasive natural material with versatile use ranging from tennis shoes over mattresses to chewing gums.
In order to be manufactured, natural latex has to be made into sheets which is achieved by adding acid to clump the material so it can be rolled. When natural latex is farmed under the supervision and without the use of pesticides it is certified as organic. Synthetic latex, which is produced using petroleum-based chemicals, is used for paints, glues and cement as it tends to solidify once the water evaporates.
Natural latex or synthetic rubber?
A focus on natural latex processing technology
Each rubber tree produces about half a cup of latex per day. It is harvested by cutting the bark of the rubber tree and accumulating it into cups. However, when mass-harvested, latex is stored in tanks. In order to extract solid rubber from the liquid latex, formic acid is added to the sap to initiate the coagulation process which can take up to 12 hours. The natural latex processing technology is fairly simple: the coagulated product is processed through a set of rollers in order to remove the excess water.
The dehydrated material is further rolled in a textured roller to create thin sheets. The latex sheets are dried by either smoking or air drying. Chemicals such as ammonia are used as a preservative for natural latex and the treatment is called prevulcanization.
Polymerization process for synthetic rubber
Synthetic latex is composed of petroleum-based chemicals linked into molecules’ strings in a process called polymerization. The reaction is triggered by combining a flammable liquid hydrocarbon called naphtha with natural gasses to produce monomers. The role of the monomers is to form polymers by binding molecules together. But that’s not the end of the story; to get the rubber substance, chemicals must be added to create polymer chains.
Synthetic latex processing technology – beyond the chemistry
Combining the purified raw materials, butadiene and the solvent hexane, and a catalyst triggers a chemical reaction which results in a white milky liquid – synthetic rubber. Depending on the desired use, it can be treated with chemicals that are added in with the help of mechanized whisks and pumps. The mixture is piped into insulated storage tanks and mixed constantly. It is coagulated in big coagulation units by boiling out the solvent mixture.
Subsequently, the water is drained by using a series of rotary and vibrating sieves, and the mixture is dried on a quivering spiral conveyor. The dried crumbs are pressed into bales using a baler machine which are processed into the final product and desired shape by using techniques such as extrusion, molding and vulcanization. The extrusion process uses the extruder to heat and compress the material, molding techniques shape the rubber by using molds, while vulcanization adds accelerators such as sulphur to make polymers more enduring.
Dandelions: the evolution in latex industry?
As a natural latex harvest annihilates forests and pollutes soil, air and water, as well as the trees being exposed to diseases and a shortage of workforce, scientists ought to find new, innovative yet more environment-friendly methods to produce latex.
As found in a study conducted by Wageningen University and Research and the Keygene company, one alternative method is extracting latex from flowers, namely dandelions, which contain a small amount of the latex needed to make rubber. In order to harvest latex from dandelion, Dutch scientists crossed the Russian dandelion, which has latex roots, with the Dutch dandelion for its size. Although the goal is to harvest 750 kilos of rubber per hectare, it is still a complex process that needs to be simplified to become profitable.