METHOD OF MAKING A SEMIFINISHED PRODUCT

Abstract

A semifinished product for making a composite fiber molded part is made by first spinning from a row of orifices of a spinning nozzle low-melting fibers of a thermoplastic. These low-melting fibers are then combined into a laminated semifinished product with high-melting reinforcement fibers of the same thermoplastic but having a melting temperature higher than the melting temperature of the low-melting fibers.

Claims

1. A method of making a semifinished product for the manufacture of a composite fiber molded part, the method comprising the steps of: a) spinning from a row of orifices of a spinning nozzle low-melting fibers of a thermoplastic; and b) combining the spun low-melting plastic fibers into a laminated semifinished product with high-melting reinforcement fibers of the same thermoplastic but having a melting temperature higher than the melting temperature of the low-melting fibers.

2. The method defined in claim 1, further comprising the step of: consolidating the semifinished product by mechanical needling, water-jet stabilization, calendering, thermobonding with hot air, adhesion, or chemical bonding.

3. The method defined in claim 1, further comprising the step after step b) of: c) applying heat or pressure to the semifinished product such that the low-melting fibers melt and form a thermoplastic material that impregnates the reinforcement fibers and forms a matrix in which the reinforcement fibers are embedded; and thereafter d) forming the laminate into a molded body.

4. The method defined in claim 1, further comprising the step, after step a) and before step (b) of: a) forming the low-melting fibers into a nonwoven.

5. The method defined in claim 1, wherein the low-melting fibers are spun as continuous filaments in step a).

6. The method defined in claim 1, wherein the low-melting fibers are formed as meltblown fibers.

7. The method defined in claim 6 wherein the meltblown fibers are biaxial.

8. The method defined in claim 1, wherein the high-melting fibers have a melting temperature at least 1 higher than a melting temperature of the low-melting fibers.

9. The method defined in claim 8, wherein the melting temperature of the high-melting fibers is at least 5 higher than the melting temperature of the low-melting fibers.

10. The method defined in claim 1, further comprising the steps of: a) forming the low-melting fibers of step a) into two layers before step b), and b) sandwiching the high-melting fibers between the layers.

11. The method defined in claim 1, further comprising the step of: c) applying heat or pressure to the semifinished product such that the low-melting fibers melt and form a thermoplastic material that impregnates the reinforcement fibers and forms a matrix in which the reinforcement fibers are embedded.

12. The method defined in claim 11, wherein after step c) the laminate is thermoformed into a finished product.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0034] The invention is described in greater detail below with reference to drawings that show only one embodiment. In the drawings, in schematic representation:

[0035] FIG. 1 shows schematically the manufacture of a laminate forming a semifinished product according to the invention,

[0036] FIG. 2 shows a device for carrying out the method according to the invention,

[0037] FIG. 3 is a section through a composite fiber molded part produced according to the invention, and

[0038] FIG. 4 is a perspective view of a composite fiber molded part produced according to the invention.

SPECIFIC DESCRIPTION OF THE INVENTION

[0039] FIG. 1 schematically shows the manufacture of a laminate 4 forming a semifinished product according to the invention. The laminate 4 here consists of a layer of high-melting reinforcement fibers in the form of a glass-fiber fabric 5 made of glass fibers 8. Low-melting fibers 10 are preferably produced in this embodiment by a biax melt-blown method. These fibers may be low-melting polypropylene fibers that are combined with the glass fibers 8 or with the glass-fiber fabric 5. Advantageously in this embodiment a biax melt-blown nonwoven 6 is laid on the glass-fiber fabric 5. According to the invention the low-melting fibers 10 or the polypropylene fibers have a fiber temperature T.sub.F in the region of the heat-distortion temperature T.sub.W of the polypropylene. It can be seen from FIG. 1 that because of their fiber temperature T.sub.F the low-melting fibers 10 combined with the glass fibers 8 or with the glass-fiber fabric 5 are so soft or flexible and malleable that they penetrate with fiber sections 11 into interstices 12 formed between the glass fibers 8 of the glass-fiber fabric 5. In this way an effective entanglement or connection between the high-melting glass fibers 8 and the low-melting fibers 10 is produced. The laminate 4 that is formed can in principle be supplied without special stabilization for further processing to form the composite molded part or the composite fiber molded part 7.

[0040] FIG. 2 shows very schematically a pressing tool 1 with two platens 2 and 3. In the embodiment a three-layer laminate 4 is between the platens 2 and 3. This laminate 4 has a central layer of high-melting reinforcement fibers in the form of a glass-fiber fabric 5. This glass-fiber fabric 5 is between two biax melt-blown nonwovens 6 made of polypropylene fibers. When the platens 2 and 3 are pressed together, heat and pressure applied to the laminate melt the low-melting polypropylene fibers. The heating temperature is selected so that only the polypropylene fibers melt and the glass fibers 8 of the glass-fiber fabric 5 on the other hand are not melted. On the contrary, the glass fibers 8 are impregnated or wetted by the thermoplastic polypropylene melt and in this way the glass fibers 8 are embedded in a matrix of thermoplastic plastic (PP). According to a preferred embodiment of the invention a composite fiber molded part 7 can be produced directly in the manner described above. A simple pressing tool 1 is shown only very schematically in FIG. 2. In principle within the scope of the invention three-dimensional or multi-dimensional molded parts with complicated structures can be produced in a simple manner with special pressing tools. The flexible handling and good draping properties of the laminate 4 contribute to this.

[0041] FIG. 3 shows a section through a composite fiber molded part 7 produced by the method according to the invention after cooling. It can be seen that the glass fibers 8 of the glass-fiber fabric 5 are completely embedded in the thermoplastic polypropylene matrix. Disruptive air inclusions are not observed and they can be avoided in a simple manner when the measures according to the invention are implemented. The composite fiber molded parts 7 produced in this way according to the invention have optimal mechanical characteristics. In FIG. 4 moreover a further composite fiber molded part 7 with multi-dimensional structure produced according to the invention is illustrated. Within the scope of the method according to the invention multi-dimensional structures can be implemented simply and without problems.