Method of accelerating the curing process in resin overflow systems for the use in casting processes

Abstract

A casting apparatus is provided. The apparatus comprises a resin overflow container for use in casting processes, comprising: a curing accelerator for a resin in the overflow container. The resin overflow container may include a compartment arranged within the overflow container. The compartment may be adapted to release the curing accelerator after the overflow container has been at least partly filled with resin. The apparatus may also include a mold; and a drain connecting the mold and the overflow container or being part of an overflow container outlet for drawing off resin of the overflow container.

Claims

1. An apparatus comprising: a resin overflow container for use in casting processes, comprising: a curing accelerator for a resin in the overflow container; a mould; and a drain connecting the mould and the overflow container or being part of an overflow container outlet for drawing off resin of the overflow container.

2. The apparatus according to claim 1, further comprising: a compartment arranged within the overflow container for the curing accelerator.

3. The apparatus according to claim 2, wherein the compartment is adapted to release the curing accelerator after the overflow container has been filled at least partly with resin.

4. The apparatus according to claim 3, wherein the compartment is a bag comprising a wall material being soluble in a resin or being meltable at a predetermined temperature.

5. The apparatus according to claim 1, wherein the resin is an epoxy resin or a vinyl based resin.

6. The apparatus according to claim 1, wherein the curing accelerator is selected from the group consisting of tertiary amines, imidazoles, ammonium salts, anhydrides, a carboxylic acid, and a combination thereof.

7. An apparatus comprising: a compartment for use in casting processes, comprising: a curing accelerator, wherein the compartment is arranged within an overflow container, and wherein the compartment is adapted to release the curing accelerator after the overflow container has been at least partly filled with resin, wherein the compartment is a bag comprising a wall material being soluble in the resin or being meltable at a predetermined temperature; a mould; and a drain connecting the mould and the overflow container or being part of an overflow container outlet for drawing off resin of the overflow container.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The FIGURE shows a schematic cross-sectional view of an RTM apparatus comprising a bag with a curing accelerator in the overflow container.

DETAILED DESCRIPTION OF INVENTION

(2) The FIGURE shows an RTM apparatus with a pure resin container A, a pure hardener or curing agent container B, a mixing unit C, a mixing bucket D, a blade mould E, and a resin overflow system S containing an overflow container F for excess resin, a hose L and an overflow container outlet hose M for discharging resin from the overflow container F. Moreover, a bag G with a curing accelerator H is provided at the bottom of the overflow container.

(3) The RTM process is done by mixing the pure resin (an epoxy resin) and the pure hardener (an amine) in the mixing unit C and pouring the resin/hardener mixture into the mixing bucket D. The resin/hardener mixture is then used for casting the blade in the blade mould E by means of a resin transfer moulding process. Of course other casting processes can be used as well.

(4) After the moulding of the blade in the blade mould E, the excess resin is collected in the resin overflow container F wherein the curing accelerator H, for example ammonium chloride NH.sub.4Cl, is placed in the bag G. After the bag G (in this example a PVB bag) has been dissolved by direct contact with the resin mixture, the ammonium chloride comes into contact with the epoxy resin. The addition of ammonium chloride initiates an anionic polymerization in the mixed epoxy, which supplements the step polymerization taking place between the amine groups in the hardener and the epoxy groups in the resin.

(5) The anionic polymerization proceeds at a lower temperature than the step polymerization, thus increasing the polymerization rate at ambient temperature in the overflow container F. The mixed epoxy in the overflow container F cures faster after the addition of the ammonium chloride because of the change of the dominating polymerization mechanism from a step polymerization to an anionic polymerization. The ammonium chloride acts in a catalytic amount. The initiation of the anionic polymerization with the first parts of excess resin filled into the overflow container F is suitable to initiate the anionic polymerization. The heat generated by this polymerization mechanism enhances the polymerization rate of the step polymerization. A continuous addition of curing accelerator H is thus not necessary unless the anionic polymerization reaction is stopped.

(6) After the hardener/resin mixture has been fully solidified by using the curing accelerator H as explained above, the resin mixture can be disposed in the usual manner. In the fully solidified status, the disposal of the excess or surplus resin in the form of a highly reactive resin/hardener mixture can be carried out safely. Because of the acceleration of the curing reaction, the total time for the process is shorter as in conventional processes.

(7) Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention. While the invention has been described with reference to VARTM processes for manufacturing wind turbine blades, other resin composite materials such as wings or rotors for airplanes, helicopters, coolers, or car parts as well as parts in the automotive industry or similar devices may also be prepared with the method of the invention. The overflow container can generally be used in the field of casting processes or resin transfer moulding processes, e.g. in vacuum assisted resin intrusion processes etc. For the sake of clarity, it is to be understood that the use of a or an throughout this application does not exclude a plurality, and comprising does not exclude other steps or elements. A container or unit can comprise a number of separate containers or units, unless otherwise stated.