Patent ES-341329-A1 (ES)
Title: Method of manufacturing heat insulating products,such as shells
IPC: B29C70/32
Filed: 1967-06-02
Abstract: A method of making a rigid thermal insulating pipe section comprises winding a mat a of mineral fibres impregnated with a polymerizable synthetic resin binder on to a rotating mandrel C, spraying an aqueous dispersion of refractory filler on to the being-wound mat, the need of movement of the mat and/or the rate of application of the filler dispersion being varied to vary the proportion of filler to fibres through the formed pipe section, and heating the formed pipe section to remove water and polymerize the resin. The impregnated mat is drawn off a supply reel b by the mandrel, which is driven by a variable speed motor d, and is sprayed by nozzles i, i1 which are mounted on a support n reciprocatively driven along the mandrel on a pulley belt r1À An aqueous dispersion of rerefractory filler is freed from a supply tank h by compressed air supply on line h2, along a supply line m, through a valve m1, and along two separate lines j, j1 each having a valve k or k1 to each spray nozzle. The supply of the dispersion to the nozzles and the rotational speed of the mandrel may be kept constant so that there is a progressive decrease in the proportion of filler to fibres through the thickness of being- formed pipe section as said section builds up thereby producing an insulating pipe section wherein the proportion of filler to fibres increases towards the bore of the section. The ratio of filler to fibres may be more radically varied by stopping the flow from nozzle i, or by varying the air pressure in the supply tank. Stopping the flow from both nozzles permits the outer layers of the pipe section to be formed without the presence of filler therein. The dispersion may be sprayed on to the mat from fixed nozzles, three rows of nozzles for spraying the mat prior to the mandrel and one nozzle for spraying the mat during rolling on to the mandrel. The proportion of filler to fibre may vary progressively or in stages across the pipe wall. In Fig. 2 (not shown), the pipe section has three zones, the radially inner two zones only having filler associated with the fibre, the highest ratio of filler to fibre being in the innermost zone with proportion of filler to fibre varying progressively towards the inside of the pipe section. In another example, the pipe comprises inner and outer zones, the outer zones having no refractory filler. The fibre of the mat is glass fibre and the aqueous refractory filler dispersion comprises an aqueous dispersion of clay with suitable fillers, binders, dispersing agents, wetting agents and other additives, specific examples being given. The resin binder may be a phenol-formaldehyde resin, a copolymer phenol-urea resin, or a phenol-melamine co-polymer resin. The formed pipe section may be heated in a hot air oven or in a dielectric loss heating device to polymerize the resin and drive off water, and a piece of woven glass may be wound about the pipe section prior to heating. The ends of the formed pipe section may be machined to form spigot and socket ends for connection in use to adjacent sections, Fig. 3 (not shown).