PROCESS FOR THE PRODUCTION OF FINISHED PARTS

Abstract

The invention relates to a process for the production of finished parts made of at least one multilayer, fiber-reinforced, flat semifinished-product structure, comprising the following steps: a) heating of the at least one multilayer, fiber-reinforced, flat semifinished-product structure at ambient pressure to a first temperature T.sub.a, where the at least one multilayer, fiber-reinforced, flat semifinished-product structure comprises at least two mutually superposed polymer layers and the individual polymer layers respectively have fiber-reinforcement and do not have coherent bonding to one another or have only partial coherent bonding to one another, and in the event that at least one of the polymer layers comprises a semicrystalline polymer the first temperature T.sub.a is higher than a melting point T.sub.m of the crystalline polymer in accordance with DIN EN ISO 11357-3:2013-04, and in the event that the at least two polymer layers comprise no semicrystalline polymer the first temperature T.sub.a is higher than a glass transition temperature T.sub.g in accordance with DIN EN ISO 11357-2:2013-09 of a polymer comprised in at least one of the at least two polymer layers, b) pressing of the heated at least one multilayer, fiber-reinforced, flat semifinished-product structure to give a finished part at a second temperature T.sub.b and at a pressure p.sub.b of at least 3 bar.

Claims

1. A process for the production of finished parts made of at least one multilayer, fiber-reinforced, flat semifinished-product structure, the process comprising: a) heating the at least one multilayer, fiber-reinforced, flat semifinished-product structure at ambient pressure to a first temperature T.sub.a, wherein the at least one multilayer, fiber-reinforced, flat semifinished-product structure comprises at least two mutually superposed polymer layers and the individual polymer layers respectively have fiber-reinforcement and do not have coherent bonding to one another or have only partial coherent bonding to one another, and in the event that at least one of the polymer layers comprises a semicrystalline polymer the first temperature T.sub.a is higher than a melting point T.sub.m of the crystalline polymer in accordance with DIN EN ISO 11357-3:2013-04, and in the event that the at least two polymer layers comprise no semicrystalline polymer the first temperature T.sub.a is higher than a glass transition temperature T.sub.g in accordance with DIN EN ISO 11357-2:2013-09 of a polymer comprised in at least one of the at least two polymer layers; and b) pressing the heated at least one multilayer, fiber-reinforced, flat semifinished-product structure to give a finished part at a second temperature T.sub.b and at a pressure p.sub.b of at least 3 bar, wherein the pressing in step b) comprises consolidation, calibration, or both.

2. The process according to claim 1, wherein before step a) less than 80% of a surface of the first polymer layer, wherein the surface faces toward the second polymer layer, has interlock bonding to the second polymer layer.

3. The process according to claim 1, wherein each of the at least two polymer layers is a fully consolidated layer.

4. The process according to claim 3, wherein, before step a), the at least two polymer layers are respectively fully consolidated via pressing at a temperature T.sub.v in the range from 240 C. to 280 C. and at a pressure P.sub.v of more than 5 bar.

5. The process according to claim 1, wherein the first temperature T.sub.a is maintained in step a) for a period of at least 5 seconds at ambient pressure.

6. The process according to claim 1, wherein the second temperature T.sub.b is the same as or higher than the first temperature T.sub.a.

7. The process according to claim 1, wherein step b) follows step a) directly.

8. The process according to claim 1, wherein the finished part in step b) is additionally in-mold-coated.

9. The process according to claim 1, wherein step b) is followed by a step c) in which the finished part is in-mold-coated or elements are injection-molded onto the finished part.

10. The process according to claim 1, wherein the heating takes place without contact.

11. The process according to claim 1, wherein the heating takes place by means of infrared radiation or in a convection oven.

12. The process according to claim 1, wherein in step b) a thickness of the finished part is established via pressing to a range of from 1 mm to 4 mm or step b) is followed by another step in which the thickness of the finished part is established via pressing to a range of from 1 mm to 4 mm.

13. The process according to claim 1, wherein the at least two polymer layers respectively comprise at least 50% by weight, based on the polymer, of polyolefins, polyvinyl polymers, styrene polymers, acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrenes, polymers of (meth)acrylic acid, polymethyl methacrylates, poly acrylates, polyacrylamides, polycarbonates, polyphenylene ethers, polyphenylene sulfides, polyether sulfones, polyether ketones, polyimides, polyquinoxalines, polyquinolines, polybenzimidazoles, polyamides, polyesters, polyurethanes, or mixtures thereof.

14. The process according to claim 1, wherein the at least two polymer layers comprise the same polymer as matrix material.

15. The process according to claim 1, wherein the at least two polymer layers respectively have reinforcement by a fiber structure.

16. The process according to claim 15, wherein fibers of the fiber structure are carbon fibers, glass fibers, aramid fibers, metal fibers, polymer fibers, potassium titanate fibers, boron fibers, or mineral fibers.

Description

EXAMPLES

Comparative Example

[0044] Two fully multilayer-consolidated semifinished-product structures were heated to 260 C. in an infrared radiation field and processed via pressing in a component mold to give in each case a finished part. The two semifinished-product structures comprised respectively six polymer layers, in each case fiber-reinforced. PA6 was used as polymer. In the first semifinished-product structure there were four polymer layers oriented parallel in respect of their fiber reinforcement, the two exterior polymer layers being parallel to one another and at an angle of respectively 90 to their adjacent layers. In the second semifinished-product structure there were also four polymer layers in total, oriented parallel. The two layers that were, seen from the outside, in second place in the six layers were parallel to one another and at an angle of 90 to the adjacent layers. PA6-GF35 was used for in-mold coating. The thickness of the finished parts was 1.5 mm.

[0045] Finished parts were produced with good optical surface properties and good mechanical properties.

Inventive Example

[0046] Three multilayer semifinished-product structures with their polymer layers mutually superposed but not bonded to one another were heated to 260 C. in an infrared radiation field and processed via pressing in a component mold to give in each case a finished part. PA6 was used as polymer. The temperature of 260 C. was maintained for from 2.5 min to 3 min before the pressing process. The semifinished-product structures comprised respectively six polymer layers, in each case fiber-reinforced. In all of the semifinished-product structures there were four polymer layers oriented parallel in respect of their fiber reinforcement, the two exterior polymer layers being parallel to one another and at an angle of respectively 90 to the adjacent layer. PA6-GF35 was used for in-mold coating. The thickness of the finished parts was 1.5 mm.

[0047] Although, unlike in the comparative example, there was no full consolidation of the multilayer semifinished-product structure upstream of finished-part production, finished parts were produced having optical and mechanical properties just as good as the properties of the finished parts of the comparative example.