Patent GB-826412-A (GB)
Title: Improvements in or relating to methods of and means for producing composite sheets comprising reinforcing material and synthetic resin
Inventor: SHORTS CALHOUN
IPC: B29C53/24
Filed: 1956-08-08
Abstract: 826,412. Moulding resin sheets. FILM INTERNATIONAL ESTABLISHMENT. Aug. 8, 1956 [April 30, 1956], No. 24253/56. Class 87(2). [Also in Group VIII] A sheet of fibre-reinforced synthetic resin is produced by a process characterised by continuously putting thermosetting resin material in a fluid state on a moving carrier band, continuously immersing the fibrous reinforcement in the resin material on the band, continuously applying a moving cover band to produce a sandwich and then continuously passing the sandwich through shaping means whilst simultaneously setting the resin material. The fibrous material may be pressed down into the resin material before applying the cover band. The carrier and cover bands may be stripped from the finished sheet. As shown, the carrier band 1 is unrolled from a roll 2 and passes along a table 3. If it is of a material (e.g. regenerated cellulose) capable of being shrunk by heat, it may be pre-shrunk by passing through a heating zone e.g. past infra-red heaters. Substantially liquid resin-forming material is deposited on the band from a trough 5, and spread uniformly across it by a doctor blade 6. The edges of the band are raised by ridges 7 to prevent the resin-forming material from overflowing them. Fibre rovings 8 are fed into a chopping machine 9 from which the chopped strands drop through a box 10 onto a belt 11 which deposits them onto the layer of resin on the band 1. From the flat table 3 the carrier band travels over upwardly convex arcuate support means comprising rollers 13. Alternatively an endless belt or the periphery of a large drum or a stationary plate may comprise the support means. At the leading edge of the arcuate support means is a roller 14, and at the discharge end a pair of co-operating squeeze rollers 15 and 16, their axes lying in a plane substantially radial to the arcuate support means. Threads or strands 17 extend from spools 18, round roller 14 over the upper side of the fibres carried by band 1 and between rollers 15 and 16. Spools 18 are spring loaded to keep the threads taut and so press the fibrous material into the resin on band 1. Ahead of rolls 15 and 16 is mounted a guide roll 19 round which a cover band 20, dispensed from a roll 21, is passed. A ribbon of glue is dropped along each side of the cover band by dispensers 22. The edge portions of bands 1 and 20 pass between short rolls 23 and rolls 24 to squeeze together their edges, the glue being sufficiently quick-setting to stick them together before they reach the rolls 15, 16. These rolls squeeze out air and reduce the sandwich to the desired thickness. Small rolls 25 press the margins against the upper roll 16. The roll 15 may be mounted stationarily and roll 16 yieldingly, e.g. by pneumatic cylinders or compression springs (not shown), so that incompressible objects will pass through without jamming the apparatus. The sheet then passes over a supporting table into the oven 30 to set the resin. During its passage through the oven, the sheet is shaped by passing it between one or more pairs of forming strips 31, 32 of complementary contour, which may be flat, corrugated (as shown), sawtoothed or of alternate ridge and channel shape. When the sheet emerges from the oven it may be cut to desired width and length by saws (not shown). The carrier band may be of regenerated cellulose, the cover band of paper or of the same material as the carrier band. The resin may be of the epoxy or unsaturated polyester (i.e. polymeric ester derived, at least partly, from an alpha-betaunsaturated dibasic acid and a glycol and dissolved in a copolymerisable monomer, e.g. stryene) type and may contain a curing catalyst. The fibrous material is preferably of glass but may be of any synthetic, inorganic, vegetable or animal fibre and may be in the form of an unwoven mat or of intermingled chopped fibres. Materials may be selected to have substantially the same refractive index so that the product may be as clear as possible.