Hybrid component part comprising a local stiffening composed of a two-stage-crosslinked polyurethane-based fibre composite material

Abstract

The invention relates to a hybrid component part comprising a local stiffening made of a two-stage-crosslinked polyurethane-based fiber composite material, more particularly to the production of such a hybrid component part. Said invention has for its object to specify a technology which makes it possible in cost-effective fashion to effect local stiffening of metal parts with a fiber composite material in order thus to obtain a hybrid component part. It is a fundamental concept of the process according to the present invention to use a particular polyurethane formulation which in a first crosslinking reaction can be converted into a thermoplastic polymer and later in a second crosslinking reaction is fully crosslinked to afford a thermoset matrix material. The thermoplastic polymer is characterized by a good adhesion to metal surfaces. The metal can be subjected to further forming with the attached thermoplastic material. The polyurethane is subsequently thermosettingly cured and achieves its final stiffness.

Claims

1. Process for producing a hybrid component part comprising the steps of: a) providing a reactive composition at least comprising: at least one hardener which is a uretdione having an NCO functionality of at least two, at least one binder which is a polyol compound having an OH functionality of 3 to 6 and which comprises at least one polar functional group selected from an ester, carbonate, amide, urethane, urea, thioester or thiocarbonate functionality; b) providing fibres; c) coating the fibres with the reactive composition; d) exposing at least the reactive composition to heat to perform a first crosslinking reaction in the course of which hardener and binder are converted into a thermoplastic polymer, thus embedding the fibres into the thermoplastic polymer; e) providing a metallic main body or a semifinished precursor thereof; f) placing the thermoplastic polymer comprising the fibres embedded therein onto a localized area of the main body/semifinished precursor thereof; g) pressing the thermoplastic polymer onto the main body/semifinished precursor thereof so that the fibres adhere to the main body/semifinished precursor thereof via the thermoplastic polymer; h) forming the semifinished precursor comprising the thermoplastic polymer adherent thereto to afford the metallic main body provided that only a semifinished precursor of the main body was provided in step e); i) exposing at least the thermoplastic polymer to heat to perform a second crosslinking reaction in the course of which the thermoplastic polymer is converted to a thermoset polymer; k) obtaining the hybrid component part comprising at least the metallic main body provided with at least one local stiffening composed of a fibre composite material, wherein the fibre composite material comprises a matrix formed from the thermoset polymer and the fibres embedded therein, wherein the thermoplastic polymer comprising the fibres embedded therein is provided in layerwise fashion, in that the layers are compressed to afford a stack in the absence of the main body/the semifinished precursor thereof and in that the sequence of steps f) and q) is effected by placing and pressing the stack onto the main body/the semifinished precursor thereof.

2. Process according to claim 1, characterized in that the second crosslinking reaction is performed at a temperature between 160 C. and 220 C.

3. Process according to claim 2, characterized in that the main body is composed of a steel which in the course of performance of the second crosslinking reaction undergoes a change and/or rearrangement of its microstructure.

4. Process according to claim 1, characterized in that the placing and/or the pressing of the thermoplastic polymer onto the main body/the semifinished precursor thereof is effected at a temperature of 20 C. to 25 C.

5. Process according to claim 2 with the proviso that a semifinished precursor of the main body is provided and formed into the main body with adherent thermoplastic polymer, characterized in that the forming of the semifinished precursor into the main body is effected at a temperature of 20 C. to 150 C., if necessary after heating of the semifinished precursor and/or by using a heated forming apparatus.

6. Process according to claim 1, characterized in that the first crosslinking reaction is performed in the absence of the metallic main body/the semifinished precursor thereof.

7. Process according to claim 6, characterized in that after performance of the first crosslinking reaction a period of one day to one year elapses before the second crosslinking reaction is performed and in that the thermoplastic polymer comprising the fibres embedded therein is stored and/or transported at temperatures between 15 C. and 30 C. over this period.

8. Process according to claim 1, characterized in that as hardener uretdiones free from blocking agents are employed which are produced from at least one of the following substances: isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diisocyanatodicyclohexylmethane (H12MDI), 2-methylpentane diisocyanate (MPDI), mixtures of 2,2,4-trimethylhexamethylene diisocyanate and 2,4,4-trimethylhexamethylene diisocyanate (TMDI), and norbornane diisocyanate (NBDI).

9. Process according to claim 1, characterized in that at least one polycaprolactone is employed as binder.

10. Process according to claim 1, characterized in that as binder at least one polyester polyol is employed which has an OH number between 20 mg KOH/g and 500 mg KOH/g, an acid number of not more than 2 mg KOH/g and a molar mass between 100 g/mol and 5000 g/mol.

11. Process according to claim 1, characterized in that the composition comprises at least one cobinder, wherein as cobinder epoxy resins are employed which are selected from the group comprising epoxy resins based on bisphenol A diglycidyl ether, epoxy resins based on bisphenol F diglycidyl ether and cycloaliphatic types, for example 3,4-epoxycyclohexylepoxyethane or 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate.

12. Process according to claim 11, characterized in that the composition comprises a hardener corresponding to the cobinder which is selected from the group comprising the following substance classes: polycarboxylic acid, polycarboxylic anhydride, aliphatic polyamines, cycloaliphatic polyamines, polyetheramines, polymercaptans or polyamidoamines.

13. Process according to claim 1, characterized in that the composition is free from substances that exhibit catalytic activity for the first and/or second crosslinking reaction.

14. Process according to claim 1, characterized in that the composition is provided in a liquid solvent, wherein the constituents of the composition are dissolved and/or suspended and/or dispersed in the solvent so that the coating of the fibres with the composition is effected by impregnating the fibres with the solvent and in that the constituents dissolved/suspended/dispersed therein, and in that the solvent is at least partly evaporated from the fibres in the course of performance of the first crosslinking reaction, wherein the solvent is an ester or a ketone or a mixture comprising at least one ester and/or at least one ketone.

15. Process according to claim 1, characterized in that the thermoplastic polymer comprising the fibres embedded therein is placed at the localized region of the main body/the semifinished precursor thereof without the use of an additional adhesive.

16. Hybrid component part comprising a metallic main body provided with at least one local stiffening made of a fibre composite material, wherein the fibre composite material comprises a polyurethane-based thermoset matrix and fibres embedded therein, characterized in that the hybrid component part has been produced by a process according to claim 1.

17. Process for producing a hybrid component part comprising the steps of: a) providing a reactive composition at least comprising: at least one hardener which is a uretdione having an NCO functionality of at least two, at least one binder which is a polyol compound having an OH functionality of 3 to 6 and which comprises at least one polar functional group selected from an ester, carbonate, amide, urethane, urea, thioester or thiocarbonate functionality; b) providing fibres; c) coating the fibres with the reactive composition; d) exposing at least the reactive composition to heat to perform a first crosslinking reaction in the course of which hardener and binder are converted into a thermoplastic polymer, thus embedding the fibres into the thermoplastic polymer; e) providing a metallic main body or a semifinished precursor thereof; f) placing the thermoplastic polymer comprising the fibres embedded therein onto a localized area of the main body/semifinished precursor thereof; g) pressing the thermoplastic polymer onto the main body/semifinished precursor thereof so that the fibres adhere to the main body/semifinished precursor thereof via the thermoplastic polymer; h) forming the semifinished precursor comprising the thermoplastic polymer adherent thereto to afford the metallic main body provided that only a semifinished precursor of the main body was provided in step e); i) exposing at least the thermoplastic polymer to heat to perform a second crosslinking reaction in the course of which the thermoplastic polymer is converted to a thermoset polymer; k) obtaining the hybrid component part comprising at least the metallic main body provided with at least one local stiffening composed of a fibre composite material, wherein the fibre composite material comprises a matrix formed from the thermoset polymer and the fibres embedded therein, wherein the thermoplastic polymer comprising the fibres embedded therein is provided in layerwise fashion and in that the sequence of steps f) and g) is accordingly carried out repeatedly to place and press on in layerwise fashion the thermoplastic polymer comprising the fibres embedded therein.

18. Process according to claim 17, characterized in that the second crosslinking reaction is performed at a temperature between 160 C. and 220 C.

19. Process according to claim 18, characterized in that the main body is composed of a steel which in the course of performance of the second crosslinking reaction undergoes a change and/or rearrangement of its microstructure.

20. Process according to claim 17, characterized in that the placing and/or the pressing of the thermoplastic polymer onto the main body/the semifinished precursor thereof is effected at a temperature of 20 C. to 25 C.

21. Process according to claim 18 with the proviso that a semifinished precursor of the main body is provided and formed into the main body with adherent thermoplastic polymer, characterized in that the forming of the semifinished precursor into the main body is effected at a temperature of 20 C. to 150 C., if necessary after heating of the semifinished precursor and/or by using a heated forming apparatus.

22. Process according to claim 17, characterized in that the first crosslinking reaction is performed in the absence of the metallic main body/the semifinished precursor thereof.

23. Process according to claim 22, characterized in that after performance of the first crosslinking reaction a period of one day to one year elapses before the second crosslinking reaction is performed and in that the thermoplastic polymer comprising the fibres embedded therein is stored and/or transported at temperatures between 15 C. and 30 C. over this period.

24. Process according to claim 17, characterized in that as hardener uretdiones free from blocking agents are employed which are produced from at least one of the following substances: isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diisocyanatodicyclohexylmethane (H12MDI), 2-methylpentane diisocyanate (MPDI), mixtures of 2,2,4-trimethylhexamethylene diisocyanate and 2,4,4-trimethylhexamethylene diisocyanate (TMDI), and norbornane diisocyanate (NBDI).

25. Process according to claim 17, characterized in that at least one polycaprolactone is employed as binder.

26. Process according to claim 17, characterized in that as binder at least one polyester polyol is employed which has an OH number between 20 mg KOH/g and 500 mg KOH/g, an acid number of not more than 2 mg KOH/g and a molar mass between 100 g/mol and 5000 g/mol.

27. Process according to claim 17, characterized in that the composition comprises at least one cobinder, wherein as cobinder epoxy resins are employed which are selected from the group comprising epoxy resins based on bisphenol A diglycidyl ether, epoxy resins based on bisphenol F diglycidyl ether and cycloaliphatic types, for example 3,4-epoxycyclohexylepoxyethane or 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate.

28. Process according to claim 27, characterized in that the composition comprises a hardener corresponding to the cobinder which is selected from the group comprising the following substance classes: polycarboxylic acid, polycarboxylic anhydride, aliphatic polyamines, cycloaliphatic polyamines, polyetheramines, polymercaptans or polyamidoamines.

29. Process according to claim 17, characterized in that the composition is free from substances that exhibit catalytic activity for the first and/or second crosslinking reaction.

30. Process according to claim 17, characterized in that the composition is provided in a liquid solvent, wherein the constituents of the composition are dissolved and/or suspended and/or dispersed in the solvent so that the coating of the fibres with the composition is effected by impregnating the fibres with the solvent and in that the constituents dissolved/suspended/dispersed therein, and in that the solvent is at least partly evaporated from the fibres in the course of performance of the first crosslinking reaction, wherein the solvent is an ester or a ketone or a mixture comprising at least one ester and/or at least one ketone.

31. Process according to claim 17, characterized in that the thermoplastic polymer comprising the fibres embedded therein is placed at the localized region of the main body/the semifinished precursor thereof without the use of an additional adhesive.

32. Hybrid component part comprising a metallic main body provided with at least one local stiffening made of a fibre composite material, wherein the fibre composite material comprises a polyurethane-based thermoset matrix and fibres embedded therein, characterized in that the hybrid component part has been produced by a process according to claim 17.

Description

EXAMPLES

(1) The invention shall now be elucidated with reference to examples.

(2) Torayca FT 300 3K 200tex carbon fibres were processed in all experiments. The fibres were in the form of a twill-weave sheetlike textile structure, manufactured by Engineered Cramer Composites (ECC), Typ Style e452. The basis weight was 200 g/m.sup.2.

(3) Metallic main bodies in the form of a miniature B-pillar supplied by Benteler Automobiltechnik were employed. The metallic main bodies are made of a hot-formed steel (22MnB5 alloy)/a readily formable aluminium alloy.

(4) In the noninventive comparative example 0 a reactive polyurethane composition was chosen which was produced as per example 2 of US2014087613A1. The formulation is reported in table 0. Since the binder does not comprise a polar functional group selected from an ester, carbonate, amide, urethane, urea, thioester or thiocarbonate functionality, the formulation is not an inventive one.

(5) For the inventive example 1 a reactive composition having a formulation as per table 1 was employed.

(6) TABLE-US-00001 TABLE 0 Formulation 0 of the reactive composition in comparative example 0 starting producer/ description weight/wt % supplier uretdione-containing hardener 65.3 Evonik Vestagon B11604 Industries (NCO content: 7.7%) binder: tetrafunctional 10.9 Perstorp polyether polyol 4640 (OHN: 630 mg KOH/g) degasifier benzoin 0.2 Aldrich butyl acetate 23.6 Fluka

(7) TABLE-US-00002 TABLE 1 Formulation 1 of the reactive composition in inventive example 1 starting producer/ description weight/wt % supplier uretdione-containing 27.7 Evonik hardener Vestagon Industries BF 1320 (NCO content: 14%) binder: tetrafunctional 21.2 Perstorp polyester Capa 4101 (OHN: 224 mg KOH/g) oxirane-containing 6.9 Momentive cobinder Epikote Resin 828 Aradur 3380 1.1 Huntsman Advanced Materials additive TegoWet 500 0.3 Evonik Industries methylisobutylketone 21.4 Fluka isopropyl acetate 21.4 Fluka

(8) The employed substances from the tables were in each case processed with a dissolver to afford a homogeneous solution, the reactive composition.

(9) To coat the sheetlike textile structure with the reactive composition the carbon fibre fabric was impregnated with the solution and then dried in an oven for 10 minutes at 150 C. The fibre volume content was 45 volume percent.

(10) The thus obtained thermoplastic polymer comprising the embedded fibres (prepreg) was then stored for approximately three weeks at 20 C. Then, four layers were respectively cut to size to dimensions of 84 cm and compressed into stacks at a temperature of 150 C. and a pressure of 3 bar (i.e. 3*10.sup.5 Pa) for 3 minutes with a Vogt LaboPress P 400 S laboratory press. After compressing, the stacks were cooled back down to 20 C.

(11) The stack produced from formulation 1 was then able to be draped into the miniature B-pillar as a local reinforcement element. On account of the intrinsic tackiness of the prepreg, pressing with hand force without additional pretreatment of the metal surface was sufficient to ensure adequate adhesion during further handling both on steel and on aluminium. An additional adhesive was not employed. Nevertheless no detachment was observed upon transport or 180 rotation of the metal part. The workpiece with the thermoplastic polymer adherent thereon was then cured in an oven at a temperature of 200 C. over 30 minutes without additional affixing. Adhesion to the metallic main body was retained and a locally thermoset-reinforced hybrid component part was thus obtained.

(12) By contrast, the adhesion of the stack produced from formulation 0 was not sufficient; the local reinforcement patch detached from the metal surface again.

(13) The comparison teaches that only the inventive polyurethane formulation is suitable for local stiffening of metal parts.

(14) In Example 1 Epikote Resin 828 (an epoxy resin) was used as a cobinder. Corresponding hardener to this cobinder was Aradur 3380 (a epoxy binder). As set out below it is shown that even without using a cobinder and a hardener corresponding to the cobinder adhesion on metal can be improved.

(15) TABLE-US-00003 TABLE 2 Formulation 2 of the reactive composition in inventive example 2 starting producer/ description weight/wt % supplier uretdione-containing 37 Evonik hardener Vestagon B11604 Industries (NCO content: 12.8%) binder: Polycaprolactone 13 Perstorp Capa 3031 (OHN: 560 mg KOH/g) solvent methylisobutylketone 25 Fluka solvent isopropyl acetate 25 Fluka

(16) TABLE-US-00004 TABLE 3 Formulation 3 of the reactive composition in inventive example 3 starting producer/ description weight/wt % supplier uretdione-containing 33 Evonik hardener Vestagon BF1320 Industries (NCO content: 14%) binder: Polycaprolactone 28 Perstorp Capa 4101 (OH N: 224 mg KOH/g) solvent methylisobutylketone 19.5 Fluka solvent isopropyl acetate 19.5 Fluka

(17) For assessment of adhesion on metal tensile shear strength has been measured according to DIN EN 1465.

(18) Test bodies have been manufactured as follows: On metal sheets made from steel DC04 ZE 75/75 and aluminium 6016 respectively each one unreacted stack consisting of four prepreg layers has been pressed and reacted. Said prepregs consisted from formulations 0, 1, 2, 3 and from carbon fibres Torayca FT 300 3K 200tex in form of a twill-weave sheetlike textile structure with a basis weight of 200 g/m.sup.2. Said stack was prepared at a pressure of 2.5*10.sup.5 Pa and a temperature of 150 C. for 5 minutes. Subjected to this conditions no cross-linking occurred. Pressing and cross-linking on metal was performed at a temperature of 200 C. and a pressure of 2.5*10.sup.5 Pa for 30 minutes. Subsequently, the setting was chilled to room temperature for 30 minutes under 2.5*10.sup.5 Pa within the press.

(19) Each five test bodies of different material combinations have been tested and measured tensile tear strength has been averaged. Results are displayed in table 4:

(20) TABLE-US-00005 TABLE 4 Results of assessment of tensile shear strength Test tensile run metal formulation shear strength I steel 0 0 MPa (not gaugeable) II aluminium 0 0.8 MPa III steel 1 9.1 MPa IV aluminium 1 7.8 MPa V aluminium 2 4.3 MPa VI aluminium 3 1.6 MPa

(21) Tensile shear strengths measured according to DIN EN 1465 are a meaningful measure for the degree of adhesion on metal achieved by the prepregs. According to the results adhesion of formulation 1 comprising cobinder and corresponding hardener is by far the strongest (compare runs III and IV with the other ones).

(22) But even formulation 2 without cobinder and corresponding hardener adheres significantly better than formulation 0 (prior art) comprising a polyether polyol (compare run V with runs I and II).