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1493836 Extruding fibre reinforced material MONSANTO CO 23 Dec 1974 [26 Dec 1973] 55391/74 Heading B5A [Also in Division F2] An extrusion of a plastic material, comprising an annular or oval tube, or a horseshoe section, has discontinuous fibres which have been oriented transversely of the direction of extrusion by extrusion from a die passage 5 defined between stationary die surfaces and which, in the extrusion direction, is of an increasing crosssectional area. The passage depth may be constant, or increase or decrease in the extrusion direction, but is such as to give a ratio of outlet to inlet area of at least two or, in an annular passage, an area ratio of greater than one for ratios of mean outlet to inlet radii which satisfy a stated formulae. The passage may diverge at 15 to 90 degrees from its axis, and preferably 40 to 90 degrees. The ratio of transverse orientation to that in the extrusion direction is expressed as the ratio of the respective Youngs Moduli, which, is one for area ratios of two, and is two or more for area ratios of three or more. In the Fig. 1 embodiment, an annular diverging passage 5 for extruding a tube, is defined between an upstream constriction 6 and a parallel land portion 4, and may be of constant, or increasing, or decreasing depth. In the Fig. 2 embodiment (not shown) a tubular diverging passage is defined from the upstream end of a mandrel mounted at webs extending across the passage. In the Fig. 5 embodiment (not shown) for extruding a tube, the passage is of constant depth and diverges perpendicularly to its axis, and the mandrel may be mounted by a cylindrical extension extending upstream from the passage, or as in the Figs. 1 and 2 embodiment, or at knives which cut the tube to form sheets at the outlet from the die. The die may define a horseshoe shape extrusion, Fig. 4, which may be flattened into a sheet for a ply of a V-belt, or comprise a pneumatic tyre carcass, in which different transverse orientation is obtained across the sheet, or a greater orientation in the sidewalls than in the crown, by corresponding variation of the outlet to inlet area ratios at these locations. The examples relate to the extrusion of hose from; (1) to (3), (5), (8), and (9) styrene butadiene rubber and wood cellulose fibre, vulcanized after extrusion in an autoclave or mould, e.g. to produce radiator hose; (4), polyvinyl chloride and wood pulp; (6) and (7), (10) and (11), wood cellulose fibre with either an unspecified elastomer, or a natural rubber blended with styrene-butadiene blend, or EPDM rubber, or styrene butadiene rubber, vulcanized in an autoclave, or EPDM rubber dried before extrusion, and cured in continuous passage from the extruder through a microwave oven, hot air oven, and liquid medium; (12), natural rubber/ styrene butadiene rubber blended with rayon fibre, vulcanized in an autoclave. The plastic material may also comprise cement or clay, various specified thermoplastics, or phenol-aldehyde thermosetting plastics, or specified rubbers. The fibres may also comprise nylon, polyester, cotton, glass, carbon, steel, potassium titanate, boron, alumina, or asbestos, and preferred aspect ratios and fibre/plastic weight ratios are specified. One tubular layer may be simultaneously extruded around another.
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