When and how does leaching occur?

Rubber components in contact with food and beverages can occur in many situations.

Location Component
Food Transportation Conveyor Belts, hoses and tubing
Pipework Seals, gaskets, flexible connectors, butterfly valves
Pumps Diaphragms, stators
Plate Heat Exchangers Gaskets
Machinery and Storage Tanks General seals and gaskets
Packaging machinery Seals and rod wipers

It is inherently undesirable for any chemical component of the rubber to migrate into a foodstuff during processing or storage. Rubber compounds are complex formulations that undergo chemical transformation during vulcanisation.

Rubber components that can potentially migrate include low molecular mass monomers, vulcanising agents, plasticisers, oils and waxes and their breakdown products. For example, polar plasticisers such as di-2-ethylhexyl phthalate are readily soluble in alcohol so plasticised rubbers should not be used in contact with alcoholic beverages.

Benefits vs. RisksThe compounds 2-mercaptobenzothiazole (MBT) and benzothiazole (BT) may migrate from rubber during the manufacture and storage of food or drink. Research has shown that this might happen. Both MBT and BT migrated from rubber into laboratory solvents.

The main types of rubber components where residues of MBT and BT may be found include natural rubber or nitrile rubber seals and gaskets used in food processing equipment. MBT is formed from two accelerators used in vulcanising rubber: 2-mercaptobenzothiazyl disulphide (MBTS) and N-cyclohexyl-2-benzothiazole sulphonamide (CBS). BT is formed by splitting a disulphide bridge in MBTS

Similarly, the acrylonitrile monomer is of concern to health authorities and is not permitted to migrate at detectable levels so levels of free monomer must be tightly controlled during production.

Rubbers intended for food contact use are normally compounded to guidelines given in legislation - but which legislation?