APPARATUS FOR SUPPLYING THERMOSETTING RESIN THROUGH CONDUITS INTO A MOULD CAVITY BEING UNDER VACUUM

Abstract: The invention relates to an apparatus for supplying thermosetting resin through at least one conduit into a mould cavity being under vacuum and partially filled with reinforcing material from below and upwards for producing elongated objects with relatively small wall thickness, the mouth of said at least one conduit is placed intially at the lowest end closure of the cavity and is then successively moved upward in a position just under the surface of the introduced resin. Said at least one conduit is according to the invention an elongated, thin pipe or cannula, preferably of metal, for producing molecular friction in the resin during the transportation of the same through the pipe at the pressure used and thereby reduce the visocisty of said resin.

Description: Apparatus for supplying thermosetting resin through conduits into a mould cavity being under vaπiinm The invention relates to an apparatus for supplying thermo¬ setting resin through at least one conduit into a mould ca- vity being under vacuum and provided with reinforcing mate¬ rial from below and upwards for producing elongated objects with relatively thin wall thickness, the mouth of said at least one conduit is placed initially at the lowest end closure of the cavity and is then successively moved upward in a position just below the surface of the introduced re¬ sin. A method for vacuum molding of objects of thermo¬ setting resin is known from SE 9002066-0 (corr. to WO 91/18725) , in which the resin is supplied through at least one hose, which is sealingly inserted through a wall in the upper portion of the mould sufficiently deep into the cavi¬ ty so that its free end is positioned in the lower portion of said cavity, and the hose or hoses are then progressive¬ ly pulled upwards at such a speed that the free end of the hose or hoses is positioned just below the surface of the resin as it is supplied and rises in the mould. When producing elongated objects made totally or partially of thermosetting resin and with a relatively small wall thickness, particularly when sheathing metal pi- pes with reinforced thermosetting resin, it is not possible to use hoses for the introduction of the resin into the mould. When a metal pipe is provided with a sheath of rein¬ forced thermosetting resin with a thickness of material of about 3-30 mm, which sheath acts as load carrier, the hoses will namely take to much space and have inregularities in the reinforcement and thereby weakenings in the sheath. The ready-mixed resin (monomer + hardening agent) cannot be heated before it is introduced into the hoses to reduce the viscosity of the resin and thereby make it easier to intro- duce said resin through said hose or hoses, since said re¬ sin then will gel in the hose or hoses and be viscous and will neither penetrate into the reinforcement nor wet the same. The object of the invention is to eliminate the abo- ve-mentioned drawbacks. According to the invention this object is achieved in that said at least one conduit is an elongated, thin pi¬ pe or cannulae with small wall thickness, preferably of me¬ tal, for producing molecular friction in the thermosetting resin during the transportation of the same through the pi¬ pe at the pressure used and thereby reduce the viscosity of said resin. As, according to the invention, the conduit or con¬ duits are elongated, thin pipes or cannulae with small wall thickness molecular friction will occur in the pipes at the pressure used when the resin is transported therethrough, which provides that the viscosity of the ready-mixed resin is lowered, whereby the very liquid resin that leaves the mouths of the pipes or cannulae will wet the reinforcement very well and fill all voids in the resinforcement and in the cavity. This heating by molecular friction is not in any way like "usual" heating of the realy-mixed resin, sin¬ ce the geling of the resin now will start at first a time after said resin has left the mouths of said pipes or can- nulae. The apparatus according to the invention is particu¬ larly used for producing composite pipes, which are made of a thin internal liner of metal, preferably stainless steel, a sheath or intermediate load carrying layer of reinforced thermosetting resin and possibly an external pipe of metal, preferably stainless steel. Such pipes are intended to be laid at the bottom of the sea or to be mounted on host oil or production platforms for transportation of especially natural gas and oil from off-shore to on-shore. The thermosetting resins used for the load carrying sheath are for instance polyester plastic, epoxy plastic etc, which are reinforced with glass fibre, carbon fibre, aramide fibre etc. When such pipes with an internal diameter of 100- 1000 mm or more are manufactured the resin used is prefe- rably polyester plastic, which is reinforced with glass fibre, so that the finished sheath will have a thickness of material of about 3-30 mm. The cannulae or pipes used for making the sheath have an external diameter of about 1-3 mm, a length of up to about 12 m and a wall thickness of about 0,2-0,5 mm. The ready mixed thermosetting resin is pumped through said cannulae or pipes with a pressure of about 30-50 MPa (300-500 bar) and the cannulae are moved out of the mould at a speed of about 0,01-3 mm/s. The mouths of said cannulae shall always be positioned under the surface of the supplied resin. At the beginning of the pumping of the resin this has a temperature of about 20°C and is heated by molecular friction in said cannulea to about 25-30°C at the mouths of said cannulea. Since the viscosity of polyester plastic is lowered with increasing temperature by about 10% per °C it is obvious that the po¬ lyester plastic which leaves the mouths of the cannulae is very liquid. The viscosity and thereby the degree of molecular friction of the resin, which leaves the mouths of the can- nulae, is determined by the composition and type of thermo¬ setting resin used, pressure, flow rate, internal diameter and length of the cannulae used. Since the cannulae or pipes used have very small ex¬ ternal diameter there will be formed no irregularities in the reinforcement of the laminate, i.e. there will be for¬ med no ridges of reinforcement material and/or resin in the laminate.

Claims: l a i s 1. Apparatus for supplying thermosetting resin through at least one conduit into a mould cavity being under vacuum and partially filled with reinforcing material from below and upwards for producing elongated objects with relatively small wall thickness, the mouths of said at least one con¬ duit is placed initially at the lowest end closure of the cavity and is then successively moved upward in a position just below the surface of the introduced resin, c h a - r a c t e r i z e d i n t h a t said at least one con¬ duit is an elongated, thin pipe or cannula, preferably of metal, for producing molecular friction in the thermoset¬ ting resin during the transportation of the same through the pipe at the pressure used and thereby reduce the visco- sity of said resin. 2. The apparatus according to claim 1, c h a r a c t e¬ r i z e d i n t h a t the pipe or pipes have an external diameter of preferably 1-3 mm, a wall thickness of prefe¬ rably 0,2-0,5 mm and a length of up to 12 m.

Inventors: THULIN DAG, THULIN, DAG
Applicants: THULIN DAG, THULIN, DAG
Application year: 1996
Main classification: B29C39
IPC codes: B29C39, B29C70