Continuous impregnation of long fibers with resin for manufacturing elongate composite elements
View Patent ↗An apparatus for manufacturing an elongate composite element in undefined lengths, the composite element containing reinforcement fibers embedded in a matrix based on a composition containing a curable resin, including a vacuum chamber, rigid-walled inlet tubing, an impregnation chamber, rigid-walled transfer tubing between the vacuum chamber and the impregnation chamber, a sizing die and, downstream of the sizing die, irradiation tubes providing radiation in the ultraviolet-visible spectrum to prepolymerize the resin.
1. A process for the continuous preparation of a long elongate composite element, containing reinforcement fibers embedded in a matrix based on a composition comprising a curable resin which is curable by ionizing radiation, wherein reinforcement fibers are formed into an arrangement which is conveyed so as to subject it, successively and in a feed direction, to the following, operations:
degassing the arrangement of fibers by the action of a vacuum in a first processing chamber;
impregnating said arrangement of fibers with said composition in a second processing chamber separate from said first processing chamber, to obtain a pre-preg containing the fibers and the composition while keeping said arrangement substantially out of contact with the atmosphere;
passing said pre-preg through a die having a cross section of predetermined area and shape, to provide said pre-preg with a predetermined shape; and
downstream of the die, stabilizing the shape of the pre-preg by at least partial polymerization by means of exposing the pre-preg resin to an ionizing treatment, wherein said ionizing exposure is stopped once index T=T gf −T gpr has fallen below 120° C. and before said index T has fallen below 30° C., T gpr being the glass transition temperature of the composition upon completion of exposure to ionizing radiation and T gf being the glass transition temperature of the composition of the final elongate composite element.
2. A process according to claim 1 , in which said composition comprises a resin curable by a peroxide and the stabilization stage is performed by means of a heat supply.
3. A process according to claim 1 , in which said composition comprises a polymerization photoinitiator and the ionizing radiation is contained within the ultraviolet-visible spectrum.
4. A process according to claim 1 , in which the at least partial polymerization at the stabilization stage continues until said composition forms a solid medium.
5. A process according to claim 1 , in which, after the stabilization stage, the composition is consolidated by subjecting the stabilized pre-preg to an increase in temperature.
6. A process according to claim 1 , in which the viscosity of said composition is adjusted, during the fiber impregnation stage, by raising the temperature of said composition.
7. A process according to claim 1 , in which the resin is selected from the group consisting of vinyl ester resins and unsaturated polyester resins.
8. A process according to claim 1 , in which the resin is an epoxy resin.
9. A process according to claim 1 , in which said composition comprises a monomer copolymerizable with the resin and in which the viscosity of said composition is adjusted by varying the proportion of monomer.
10. A process according to claim 9 , in which said monomer is styrene.
11. A process according to claim 3 , in which said polymerization photoinitiator is the oxide of bis(2,4,6-trimethylbenzoyl)phenyl phosphine.
12. A process according to claim 1 , in which the reinforcement fibers are selected from the group consisting essentially of high-tenacity polyacrylic fibers, oxidized polyacrylonitrile fibers, high-tenacity polyvinyl alcohol fibers, aromatic polyamide fibers, polyamide-imide fibers, polyimide fibers, chlorofibers, high-tenacity polyester fibers, aromatic polyester fibers, high-tenacity polyethylene fibers, high-tenacity polypropylene fibers, cellulose fibers, rayon fibers, high-tenacity viscose fibers,
polyphenylene benzobisoxazole fibers, polyethylene naphthenate fibers, glass fibers, carbon fibers, silica fibers, ceramic fibers.
13. A process according to claim 1 , in which the reinforcement fibers are glass fibers.
14. A process according to claim 1 , in which the stabilized pre-preg is covered with a layer of resorcinol/formaldehyde latex (RFL) adhesive.
15. A process according to claim 14 , in which said layer of RFL adhesive is dried without reaching a temperature greater than 100° C.
16. A process according to claim 1 , in which the pre-preg stabilization step proceeds while the pre-preg is completely Out of contact with a support.
17. A process according to claim 1 , in which the pre-preg stabilization step proceeds while the pre-preg is in constant slip-free contact with a support.
18. A process according to claim 1 , in which said arrangement comprises long fibers parallel to a preferential reinforcement direction of said elongate composite element.
19. A process according to claim 1 , in which the surface area of the combined cross section of the fibers of said arrangement is less than 80% of the surface area of the cross section of said die.
20. A process according to claim 1 , in which the stabilizing step is performed in an inert atmosphere.
21. A process for the continuous preparation of a long elongate composite element, containing reinforcement fibers embedded in a matrix based on a composition comprising a curable resin which is curable by ionizing radiation, wherein reinforcement fibers are formed into an arrangement which is conveyed so as to subject it, successively and in a feed direction, to the following, operations:
degassing the arrangement of fibers by the action of a vacuum in a first processing chamber;
impregnating said arrangement of fibers with said composition in a second processing chamber separate from said first processing chamber, to obtain a pre-preg containing the fibers and the composition while keeping said arrangement substantially out of contact with the atmosphere;
passing said pre-preg through a die having a cross section of predetermined area and shape, to provide said pre-preg with a predetermined shape; and
downstream of the die, stabilizing the shape of the pre-preg by at least partial polymerization by means of exposing the pre-preg resin to an ionizing treatment, wherein said ionizing exposure is stopped once index D=D i /D f has reached a value of the order of 0.5 and before said index D has reached a value of the order of 0.7, D i being the Shore D hardness of the composition upon completion of exposure to ionizing radiation and D f being the Shore D hardness of the composition of the final elongate composite element.
22. A process according to claim 1 , in which said composition comprises a resin curable by a peroxide and the stabilization stage is performed by means of a heat supply.
23. A process according to claim 21 , in which said composition comprises a polymerization photoinitiator and the ionizing radiation is contained within the ultraviolet-visible spectrum.
24. A process according to claim 21 , in which the at least partial polymerization at the stabilization stage continues until said composition forms a solid medium.
25. A process according to claim 21 , in which, after the stabilization stage, the composition is consolidated by subjecting the stabilized pre-preg to an increase in temperature.
26. A process according to claim 21 , in which the viscosity of said composition is adjusted, during the fiber impregnation stage, by raising the temperature of said composition.
27. A process according to claim 21 , in which the resin is selected from the group consisting of vinyl ester resins and unsaturated polyester resins.
28. A process according to claim 21 , in which the resin is an epoxy resin.
29. A process according to claim 21 , in which said composition comprises a monomer copolymerizable with the resin and in which the viscosity of said composition is adjusted by varying the proportion of monomer.
30. A process according to claim 29 , in which said monomer is styrene.
31. A process according to claim 23 in which said polymerization photoinitiator is the oxide of bis(2,4,6-trimethylbenzoyl)phenyl phosphine.
32. A process according to claim 21 , in which the reinforcement fibers are selected from the group consisting essentially of high-tenacity polyacrylic fibers, oxidized polyacrylonitrile fibers, high-tenacity polyvinyl alcohol fibers, aromatic polyamide fibers, polyamide-imide fibers, polyimide fibers, chlorofibers, high-tenacity polyester fibers, aromatic polyester fibers, high-tenacity polyethylene fibers, high-tenacity polypropylene fibers, cellulose fibers, rayon fibers, high-tenacity viscose fibers,
polyphenylene benzobisoxazole fibers, polyethylene naphthenate fibers, glass fibers, carbon fibers, silica fibers, ceramic fibers.
33. A process according to claim 21 , in which the reinforcement fibers are glass fibers.
34. A process according to claim 21 , in which the stabilized pre-preg is covered with a layer of resorcinol/formaldehyde latex (RFL) adhesive.
35. A process according to claim 31 , in which said layer of RFL adhesive is dried without reaching a temperature greater than 100° C.
36. A process according to claim 21 , in which the pre-preg stabilization step proceeds while the pre-preg is completely out of contact with a support.
37. A process according to claim 21 , in which the pre-preg stabilization step proceeds while the pre-preg is in constant slip-free contact with a support.
38. A process according to claim 21 , in which said arrangement comprises long fibers parallel to a preferential reinforcement direction of said elongate composite element.
39. A process according to claim 21 , in which the surface area of the combined cross section of the fibers of said arrangement is less than 80% of the surface area of the cross section of said die.
40. A process according to claim 21 , in which the stabilizing step is performed in an inert atmosphere.