Patent EA-004119-B1 (EA)
Title: Method and installation for producing centrifugally cast glass-fibre reinforced tubes
Inventor: CARLSTROM BORGE
IPC: B29C41/04
Filed: 2001-04-26
Abstract: 1. Method of manufacturing centrifuged glass fibre-reinforced synthetic material pipes, wherein liquid curable resin, which can contain a filler, together with glass fibres and additives for the curing process, possibly also with sand, is introduced into a rotating mould, characterized in that with respect to the mould temperature as the raw materials are introduced, the quantity and type of additives are adapted in a successive manner, so that gelling commences in the outer part of the pipe when the last part of the raw materials is introduced, upon gelling the temperature is lower in the outer part than in the inner part, and the gelling only commences in the inner part of the pipe after all of the raw materials have been introduced. 2. Method according to claim 1, characterized in that gelling only commences in the outer part at least three minutes after all of the raw materials have been introduced. 3. Method according to claim 1 or 2, characterized in that warm water at a temperature of at least 50 degree C. is sprayed on to the mould after gelling has commenced in the outer layer of the pipe. 4. Method according to any one of the claims 1 to 3, characterized in that an inhibitor is used in a quantity, which is between 38% and 61% of the quantity, which prevents heat development. 5. Method according to any one of the claims 1 to 4, characterized in that a more reactive catalyst mixture is used in the outer part of the pipe than in the inner part of the pipe. 6. Method according to any one of the claims 1 to 5, characterized in that the inhibitor is added in the feeder in one of the mixers. 7. Method according to any one of the claims 1 to 6, characterized in that an accelerator is added to the body resin in the second mixer (M-2) at the front in the feeder. 8. Method according to any one of the claims 1 to 7, characterized in that the accelerator is added to the liner resin in the third mixer (M-3) at the front. 9. Method according to any one of the claims 1 to 8, characterized in that the inhibitor is added to the body resin at the rear in the mixer (M-4). 10. Method according to any one of the claims 1 to 9, wherein two catalyst pumps are used, characterized in that in one pump a catalyst or a catalyst mixture having a low light-off temperature is used in the outer part of the pipe and the other is used in the inner part of the pipe. 11. Method according to claims 1-10, characterized in that the sand amount, which is necessary for obtaining the stiffness, is partitioned to a plurality of layers so that all glass fibre layers except the blocking layer are positioned between the sand layers in which the roving content is increased by pressurizing the sand layers effected by the centrifugal force. 12. Method according to claim 11, characterized in that the individual sand layers except the sand layer in the middle of the pipe wall (neutral zone) are not larger than 15% of the wall thickness of the pipe. 13. Method according to claim 11 or 12, characterized in that the individual sand layers, except the sand layer in the neutral zone, are not larger than 0.0025 times the outer diameter. 14. Method according to any one of the claims 11 to 13, characterized in that the individual layers having a glass fibre-reinforcement are not larger than 0.005 times the outer diameter. 15. Method according to any one of the claims 11 to 14, characterized in that the layers having glass fibre-reinforcement in the circumferential direction except the blocking layer are less than 1.5 mm and not more than 3.5 mm. 16. Installation for the purpose of manufacturing centrifuged glass fibre-reinforced synthetic material pipes, wherein the raw materials are introduced from an injection machine into a rotating mould, the injection machine can be moved in a fixed position, the centrifugal machines are, however, mounted on a carriage which can be moved in a transverse manner with respect to the injection machine in the same plane, warm water is used of the purpose of heating up the mould, characterized in that the spraying devices are disposed in fixed positions and cannot be moved with the moulds and water is collected under each mould in separate collecting basins, which can be moved with the mould, and said water is conveyed further into a fixed channel. 17. Installation according to claim 16, having an injection machine for the purpose of feeding raw materials into the moulds, wherein a mixer (M-1) is provided at the front for the purpose of supplying catalysts, characterized in that a mixer (M-4) is also provided at the rear in the injection machine for the purpose of introducing further additives into the body resin. 18. Installation according to claim 17, characterized in that at least one further mixer (M-2 or M-3) is provided at the front in the injection machine. 19. Centrifuged glass fibre-reinforced synthetic material pipe, comprising a plurality of layers consisting of glass fibres, curable resin, which can contain a filler, glass fibres, sand and additives, characterized in that the sand amount, which is necessary for obtaining the stiffness, is partitioned to a plurality of layers so that all glass fibre layers except the blocking layer are positioned between the sand layers in which the roving content is increased by pressurizing the sand layers effected by the centrifugal force and having thickness of at least 2 mm, blocking layer is roving layer with glass fibre content of 40%. 20. Plastic pipe according to claim 19, characterized in that the individual sand layers except the sand layer in the middle of the pipe wall (neutral zone) are not larger than 15% of the wall thickness of the pipe. 21. Plastic pipe according to claim 19 or 20, characterized in that the individual sand layers, except the sand layer in the neutral zone, are not larger than 0.0025 times the outer diameter. 22. Plastic pipe according to any one of the claims 19 to 21, characterized in that the individual layers having a glass fibre-reinforcement are not larger than 0.005 times the outer diameter. 23. Plastic pipe according to any one of the claims 19 to 22, characterized in that the layers having glass fibre-reinforcement in the circumferential direction, except the blocking layer are less than 1.5 mm and not more than 3.5 mm.