GB808435A - Bonding process - Google Patents

Abstract

A process for bonding polythene to substrates is characterized by the interposition of a vulcanizable blend of natural or synthetic rubber and polythene between the polythene and the substrate, and by the vulcanization of this blend during the bonding process, e.g. by heating in a press at 141 DEG C. The vulcanizable blend preferably contains between 40 and 60 per cent of polythene. The polythene preferably has a molecular weight greater than 13,000. The blend may be made by blending at a temperature about that of the melting point of the polythene. A curing agent (e.g. sulphur) and, if desired, other ingredients commonly used in the compounding of vulcanizable rubber blends are incorporated. These include activators, accelerators, fillers, pigments and antioxidants. The vulcanizable blend may be interposed between the polythene and the substrate in solid form, e.g. as a layer thereof, or it may be painted on as a solution in a solvent, or both methods may be used in combination. A known bonding agent (e.g. 4 : 41 : 411 - triisocyanatotriphenylmethane or other isocyanates, phenol-formaldehyde condensates or rubber derivatives) may be used to bond the vulcanizable blend to the substrate. The substrate may be a metal (e.g. mild steel, iron, brass, aluminium, copper), a textile fabric, leather, stone or a ceramic material. The process may be used for lining tanks, vats, pans or other vessels or in the production of electrical equipment. When the substrate is a suitable fabric, a structure suitable for conveyer belting for the conveyance of corrosive or chemically active materials may be obtained.ALSO:A vulcanizable composition comprises a blend of natural or synthetic rubber, e.g. a butadiene-styrene copolymer, and polythene. The blend preferably contains between 40 and 60 per cent of polythene. The polythene used may be any solid polymer of ethylene made by a high- or low-pressure process. The polythene preferably has a molecular weight greater than 13,000. The blend may be made by blending at a temperature about that of the melting point of the polythene on standard rubber-mixing machinery for example on an open mill or on a Banbury mixer. When the polythene and rubber have been blended, and the resulting blend cooled, there is incorporated therein a curing agent (e.g. sulphur) and, if desired, other ingredients commonly used in the compounding of vulcanizable rubber blends. These include activators, accelerators, fillers such as china clay, pigments and antioxidants. The composition may be interposed between polythene and various substrates (see Group VIII) either in solid form, e.g. as a layer thereof, or it may be painted on as a solution in a solvent, or both methods may be used in combination. The composition is then vulcanized to join the polythene to the substrate.