Method for Recycling Fiber-Reinforced Composite Materials

Abstract

The invention relates to a method for recycling fiber composite materials, in which items containing fiber composite material are fed into an impact reactor and comminuted by mechanical loading, wherein the comminution is carried out in such a way that fiber needles with adhering matrix are produced as the comminution product.

Claims

1. A method of reprocessing fibre fiber composite materials, the method comprising: feeding items containing fiber composite material into an impact reactor; and comminuting the items by mechanical loading, wherein the comminution is carried out in such a way that fiber needles with adhering matrix are produced as a comminution product.

2. The method according to claim 1, wherein said comminution product contains fiber needles with a fiber length of 0.1 mm to 20 mm.

3. The method according to claim 1, wherein a grading curve is determined in relation to a quantity of the comminution product by using a mesh analysis.

4. The method according to, claim 1, wherein said comminution product is discharged from said impact reactor continuously.

5. The method according to claim 1, wherein said impact reactor has ejection openings.

6. The method according to claim 5, wherein said ejection openings are covered with slotted or perforated cover plates

7. The method according to, claim 1, wherein said fiber composite materials contain at least one of glass fibers, carbon fibers, basalt fibers and aramid fibers.

8. The method according to, claim 1, wherein said comminution product contains carbon fibers with adhering finish and adhering matrix.

9. The method according to claim 1, wherein the items are sent for pre-comminution prior to comminution in said impact reactor.

10. The method according to claim 1, wherein said comminution product is mixed with a new matrix and processed to form molded parts.

11. A molded body compromising fiber needles which can be obtained by the method according to claim 1, and matrix.

12. A method of reprocessing fiber composite materials, comprising: placing structural components comprising fibers and a matrix into an impact reactor; mechanically degrading the structural components into a comminuted product in the form of fiber needles with adhering matrix; determining the size of said comminuted product with at least one of a slotted and perforated cover plates; discharging said comminuted product out of said impact reactor wherein the size of said comminuted product is adjustable to maximize the fiber needles and adhering matrix ratio.

13. The method of claim 12 further comprising classifying the comminuted product with a classifying device having screens of decreasing mesh width to sort said comminuted product according to a fiber length.

14. The method of claim 12, wherein said comminuted product comprises fibers consisting of a fiber material and a matrix adhering to said fiber material.

15. The method of claim 14, wherein said fiber needles are embedded into the matrix wherein said fiber material has edges with an irregular shape.

16. The method of claim 12, further comprising mixing a new matrix with the comminuted product to produce new molded parts.

17. The method of claim 12 further compromising molding of a new product by mixing of fractions of said commination product with a new matrix wherein said new product has uniform product properties consistent with said structural components prior to reprocessing.

18. The method of claim 17, wherein the mixing step is accomplished by using a stirrer or a mixer.

19. The method of claim 12, wherein a new molded part made from said comminuted product has an average matrix weight of about 50%.

20. A method of reprocessing fiber composite materials, comprising: placing structural components into an impact reactor; mechanically degrading the components into a comminuted product in form of fiber needles with adhering matrix; determining the size of said comminuted product with at least one of slotted and perforated cover plates; discharging said comminuted product out of said impact reactor wherein the size of said comminuted product is adjustable to maximize the fiber needles and adhering matrix ratio; reprocessing said comminuted product into a new material with added matrix of less than 15% of total weight.

Description

[0035] The method in accordance with the invention is explained in more detail hereinunder with the aid of the FIGURE which schematically shows in:

[0036] FIG. 1 an impact reactor for carrying out the method in accordance with the invention.

[0037] FIG. 1 shows an impact reactor 1, or an impact reactor arrangement for comminuting items which contain fibre composite material.

[0038] The starting material is e.g. rotor blades of wind turbine installations which comprise structural components in the form of embedded profiles made of fibre composite material made from carbon fibres. Such rotor blades can have a length of 60 m. In order for the material to be able to be supplied to the impact reactor 1, pre-comminution of the rotor blades is first carried out, in which block-like items are produced. The pre-comminution is effected by sawing.

[0039] Prior to comminution, the starting product has about 35 wt. % of matrix and 65 wt. % of fibre material in the form of carbon fibres. The matrix consists of thermosetting synthetic resin and forms a strong composite with the carbon fibres.

[0040] The impact reactor 1 comprises a floor 10 and a cylindrical casing 2 made from metallic material. A rotor 3 which is provided with impact elements 5 is arranged in the floor region, in the interior of the casing 2. The rotor 3 is operatively connected to an electric motor 6 which is arranged outside the casing 2. The shaft connecting the rotor 3 to the electric motor 6 extends in the axial direction of the cylindrical casing 2. The rotor 3 is provided with blades 4 which protrude radially from the shaft. Impact elements 5 are disposed at the ends of the free blades 4. The impact elements 5 are interchangeably fastened to the blades 4.

[0041] On the end face facing away from the rotor, the impact reactor 1 is closed with a cover 7 so that the floor 10, casing 2 and cover 7 enclose an impact reactor chamber. The cover 7 has a filling opening 9 for introducing the items. At the level of the rotor 3, the casing 2 is further provided with an ejection opening 8 for discharging the comminution products. Perforated cover plates 11 are inserted into the ejection opening 8. The cover plates 11 form screens which comminution products of the desired particle size pass through.

[0042] For comminution purposes, the pre-comminuted items are fed into the impact reactor chamber via the filling opening 9. Under the action of the rotor 3 provided with the impact elements 5 the items are comminuted to form comminution products in the form of fibre needles and discharged from the impact reactor chamber via the ejection opening 8. The removal of the comminution product from the impact reactor chamber takes place continually in the present embodiment. The fibre needles are thus discharged immediately after the desired fibre length is achieved.

[0043] Alternatively, the ejection opening can also be closable by a flap and so the device is also suitable for batch-wise operation.

[0044] The comminution products in the form of fibre needles have a fibre length of 0.1 mm to 10 mm. The fibre needles consist of a fibre material and matrix adhering to the fibre material. The fibre material in turn consists of fibre bundles and of size, which permits firm adhesion of the matrix to the fibre material. In this respect, the fibre needles are still a composite material made from fibre material and matrix. The fibre material is embedded into the matrix, wherein, by reason of comminution, the fibre needles have sharp-edged and irregular break edges, which improves the adhesion of new matrix.

[0045] After the comminution in the impact reactor 1, a mesh analysis is carried out using a fraction of fibre needles and a grading curve is determined. In this way the fibre length distribution of the fraction is known and, by mixing different fractions, a mixture of fibre needles with a preset fibre length distribution can be produced. The mesh analysis is carried out by screening the fibre needles in screens of decreasing mesh width.

[0046] In order to produce new moulded parts, fibre needles with a desired fibre length distribution are mixed with new matrix in a stirrer. The new matrix preferably consists of thermoplastic resin. After mixing, forming in a press is carried out. Heat can be supplied in so doing. After hardening of the new matrix, the new moulded part is formed.

[0047] The method is suitable in particular for producing sheet goods, profiles or three-dimensional moulded parts with a fibre composite made of reprocessed fibre needles. The moulded body newly produced from the comminuted fibre needles has a total of 50 wt. % of matrix. The quantity of the newly added matrix amounts to merely 15 wt. %. The quantity of the fibre portion amounts to 50 wt. %. The fibre lengths of the fibre needles used in this case amount to 1 mm to 10 mm.

[0048] The moulded body can also be formed as a multi-layer body. In that case, at least one layer comprises fibre needles. The moulded body can be formed as a sandwich and comprise, in addition to layers of fibre needles, further layers of fibre material, e.g. in the form of a textile. The layer of fibre needles can form a middle layer. A moulded body of this type has a particularly high level of strength and good visual appearance.

[0049] It is also advantageous that a moulded body with fibre needles produced in accordance with the invention can be sent again for reprocessing.

[0050] The fibre needles can also form an additive in elastomeric articles e.g. in rubber articles such as tyres and the like.