Multi-Component Fibre and Production Method

Abstract

The invention relates to a method for producing a multicomponent fiber, wherein the fiber is formed from a plurality of filaments, where the filaments each have a core and a thermoplastic sheath, and where the sheath is generated during the production of the filaments by in situ polymerization of monomers or oligomers of the thermoplastic on the surface of the core, and also to multicomponent fibers produced accordingly and to organosheets produced therefrom.

Claims

1. A method for producing a multicomponent fiber, wherein the fiber is formed from a plurality of filaments, where the filaments each have a core and a thermoplastic sheath, and where the sheath is generated during the production of the filaments by in situ polymerization of monomers or oligomers of the thermoplastic on the surface of the core.

2. The method as claimed in claim 1, wherein the core of the filaments is produced by die drawing methods or spinning methods.

3. The method as claimed in claim 1, wherein the core of the filaments is formed of glass, basalt, ceramic, metal, or plastic.

4. An apparatus for producing a multicomponent fiber, comprising the following components: a plurality of dies for forming the cores of a plurality of filaments, at least one applicator for applying monomers or oligomers of a thermoplastic to the cores of the filaments, at least one source of energy or radiation for in situ polymerization of the monomers or oligomers of the thermoplastic, and an apparatus for assembling the filaments into a filament bundle, thereby forming the multicomponent fiber.

5. A multicomponent fiber wherein the multicomponent fiber is formed of a plurality of filaments, where the plurality of filaments each have a core and a thermoplastic sheath.

6. The multicomponent fiber as claimed in claim 5, where the core of the filaments has a diameter in the range from ≥2 μm to ≤50 μm and/or the thermoplastic sheath has a thickness in the range from ≥0.1 μm to ≤5 μm.

7. The multicomponent fiber as claimed in claim 5, wherein the fiber is a two-component fiber.

8. A method for producing a consolidated, thermoplastic, semifinished, continuous fiber reinforced product or a component comprising it, the method comprising the steps of: producing a multicomponent fiber by the method as claimed in claim 1, producing a fabric from the multicomponent fiber, making up the fabric, and consolidating the made-up fabric into a consolidated, thermoplastic, semifinished, continuous fiber reinforced product or a component comprising it.

9. A consolidated, thermoplastic, semifinished, continuous fiber reinforced product comprising a multicomponent fiber as claimed in claim 5.

10. The semifinished product as claimed in claim 9, wherein the volume fraction of the cores of the multicomponent fiber is in the range from ≥75 vol % to ≤91 vol %, based on a total semifinished product volume of 100 vol %.

11. A method for producing short fiber reinforced components, the method comprising the steps of: producing a multicomponent fiber by the method as claimed in claim 1, chopping up the multicomponent fiber into short fibers, producing a fabric from the short fibers, and making up the fabric into a short fiber reinforced component.

12. The method as claimed in claim 1, wherein the core of the filaments is formed of glass.

13. The multicomponent fiber as claimed in claim 7, wherein the fiber is a thermoplastic-glass fiber.

14. A consolidated, thermoplastic, semifinished, continuous fiber reinforced product comprising a multicomponent fiber obtainable by the method of claim 1.

15. The semifinished product as claimed in claim 10, wherein the volume fraction of the cores of the multicomponent fiber is in the range from ≥75 vol % to ≤80 vol %.

16. The semifinished product as claimed in claim 10, wherein the volume fraction of the cores of the multicomponent fiber is in the range from ≥80 vol % to ≤90 vol %.

Description

[0052] In the drawings

[0053] FIG. 1 shows a schematic representation of an apparatus for producing a two-component fiber according to one embodiment of the invention, in a facing view in FIG. 1a) and also a side view in FIG. 1b). FIG. 1c) shows a side view of another embodiment.

[0054] FIG. 2 shows a schematic representation of a two-component fiber according to one embodiment.

[0055] FIG. 3 shows a schematic representation of a cross section through an organosheet according to one embodiment of the invention.

[0056] FIG. 4 shows a photograph of an organosheet in FIG. 4a) and also SEM micrographs of an organosheet in FIG. 4b) and of a thermoplastic-glass fiber taken therefrom, in FIG. 4c). FIG. 4d) shows EDX spectra of the areas marked in FIG. 4b).

[0057] A spinning line for producing a two-component fiber is shown in a facing view in FIG. 1a) and in a side view in FIG. 1b). It is possible therewith to modify a glass fiber drawing method and extend it to include in situ polymerization. Glass pellets are passed from a reservoir container to furnace 1 (bushing). There the glass is metered and melted. The melt emerges through dies between cooling fins 2 and so solidifies. The glass forms the core of the filaments composed of core and thermoplastic sheath, and is in turn likewise in filament form. The glass cores 3 are subsequently passed through an applicator having a sizing roll 4 and a sizing trough 5 for applying monomers or oligomers of a thermoplastic. Applied there to the glass filaments 3 is a solution comprising monomers and a UV initiator. These filaments are then irradiated with UV light by means of a UV lamp 6 as energy source or radiation source, so generating a thermoplastic sheath on the surface of the glass filaments 3 by in situ polymerization of the monomers. The sheathed filaments then pass through a second sizing apparatus with aftersizing roll 7 and sizing trough 8, for applying an additional aqueous solution, such as a finish or a coating, preferably a solution comprising silanes, after which a two-component fiber is manufactured from the individual filaments in the assembling station 9. This two-component fiber passes through a thread guide 10 to a reel 11, where the fiber is wound and provided for further processing.

[0058] FIG. 1c) shows another embodiment of an apparatus in a side view. In this embodiment, monomers of the thermoplastic are applied to the glass filaments 3 by a plurality of separate applicators each with a sizing roll 4 and a sizing trough 5. In this embodiment, the sheathed filaments are assembled to form the two-component fiber after the in situ polymerization initiated by the UV lamp 6, without aftersizing.

[0059] FIG. 2 shows a schematic representation of a cross section through two-component fibers 15 produced in this way, with a glass core 13 and a thermoplastic sheath 12, in the form in which the fibers are wound on a reel, for example. FIG. 3 shows a schematic representation of a cross section through a consolidated organosheet 20. In evidence are the uniform distribution and complete sheathing of the glass cores 13 in the thermoplastic matrix of the organosheet.

EXAMPLE 1

Radical Polymerization of Various Monomer Compositions

[0060] At room temperature (20±2° C.), in preliminary tests, acrylates and other vinyl containing monomers such as styrene, and combinations of these compounds, were admixed with the UV initiator Irgacure® 651 (2,2-dimethoxy-1,2-diphenylethan-1-one, Ciba Specialty Chemicals Inc.). The initiator fraction here was 5 m %, based on the total mass of monomer and photoinitiator. In parallel batches, up to 2.5 m % of triethanolamine (TEA) was added as transfer reagent, and the batches were stirred at 500 rpm in a closed, opaque vessel for 15 minutes at room temperature (RT) or 45° C. The precursor systems were investigated in batches each of 10 mL for their cure times, using the Aktiprint Mini 12 lamp from Eickmeyer GmbH. The power of the emitter was 80 W/cm. The distance between the glass filaments and the center point of the emitter was 4 cm. The cure times were also investigated using the Lighthammer 6 lamp from Heraeus Noblelight Fusion UV Inc. The power of the emitter was 200 W/cm. The distance between the glass filaments and the center point of the emitter was 4 cm.

[0061] Tables 1 and 2 below summarize the time taken for at least 99% polymerization (U>99%) under the various conditions tested for each of the monomers and comonomer compositions tested.

TABLE-US-00001 TABLE 1 Results of polymerization of monomers Time to U > 99% [s] 80 W/cm 200 W/cm 80 W/cm 80 W/cm Monomer RT RT 45° C. RT + TEA Hydroxyethyl acrylate <1 <<1 <<1 <<1  (HEA) Ethyl acrylate 5 2 2 — tert-Butyl acrylate 10 4 3 — (t-BuA) Hydroxyethyl 28 12 9 12 methacrylate Methyl methacrylate 40 14 10 15 Methacrylic acid 60 23 18 — Butyl acrylate 58 22 16 — Isooctyl acrylate 62 20 18 — Styrene 89 34 23 33 N-Vinylpyrrolidone 300 134 104 — Cyclohexyl acrylate 300 141 97 —

TABLE-US-00002 TABLE 2 Results of polymerization of comonomer compositions Time to U > 99% [s] Comonomer 80 W/cm 200 W/cm 80 W/cm 80 W/cm compositions RT RT 45° C. RT + TEA 0% HEA + 100% t-BuA 10 4 3 — 25% HEA + 75% t-BuA 5 2 2 2 40% HEA + 60% t-BuA 1 <1 <1 <1 50% HEA + 50% t-BuA 1 <1 <1 <1 100% HEA + 0% t-BuA <1 <<1 <<1 <<1

[0062] As can be seen from tables 1 and 2, not only acrylates and methacrylates but also vinyl-containing compounds and combinations were successfully polymerized. Copolymerizations of these compounds were also successful. The addition of triethanolamine (TEA) increased the reaction rate, but was not essential for the polymerization. Incorporation of nanoscale polymer particles into these systems was also tested, and was possible.

EXAMPLE 2

Production of an Organosheet

[0063] Glass fibers were spun on a glass fiber spinning line (LIPEX Anlagentechnik und Handel GmbH) The raw glass material took the form of beads having a diameter of 20 mm±0.1 mm. The glass composition of the raw material is summarized in table 3 below:

TABLE-US-00003 TABLE 3 Glass composition SiO.sub.2 Al.sub.2O.sub.3 Fe.sub.2O.sub.3 CaO MgO R.sub.2O B.sub.2O.sub.3 54.1 ± 14.6 ± <0.5% 16.6 ± 4.6 ± <0.8% 6.7 ± 0.5% 0.4% 0.3% 0.3% 0.5% R = lithium/sodium/potassium

[0064] The molten glass flowed at 1240° C. through 203 die apertures each having a diameter of 1 mm. At takeoff speeds of >1000 m/min, the filaments were first guided via a sizing roll. The speed of the sizing roll in this case was 4 m/min. The size used was a monomer system containing 10 mL of hydroxyethyl acrylate, 0.505 g of Irgacure® 651, and 0.253 g of TEA (triethanolamine). The in situ polymerization was initiated by means of the Aktiprint Mini 12 UV lamp (Eickmeyer GmbH) at an emitter power of 80 W/cm. The filaments were subsequently assembled into the fiber and wound by means of a reel. The spinning operation was conducted over 8 hours without spin break. The cross section of the overall fiber bundle here was 1.5 mm×2 mm. The linear density of the yarn was 50 tex.

[0065] The two-component fiber was subsequently wound from the reel and placed by hand into a pneumatic press comprising a pressing tool, a thermal conditioning device, and a suction apparatus, and was cut to dimensions of 5 cm×1.5 cm.

[0066] The temperature in the cavity was adjusted using the TT-390 thermal conditioning device (TOOL-TEMP AG, Sulgen, Switzerland). Heat transfer into the press cavity took place using the TOOL-THERM SH-3 heat transfer oil (TOOL-TEMP AG, Sulgen, Switzerland). This oil is heated or cooled in the thermal conditioning device and passed via hoses through the holes in the tool. The indirect thermal conditioning system possessed a heating power of 24 kW and a cooling power of 90 kW at 360° C. The temperature was measured and controlled by way of the thermal conditioning device. The housing containing the suction apparatus completely surrounded the press and thermal conditioning device. This allowed the press to be employed at high temperatures, since the gases given off from the thermal conditioning device were drawn off directly under suction. The heating and cooling system represents the connection between the thermal conditioning device and the tool.

[0067] The tool stroke h.sub.W describes the maximum opening of the tool. The thickness of the material inserted into the cavity is therefore limited to this stroke. The cavity describes the region which is filled with the material for consolidation. The press cavity used was 260 mm long, 60 mm wide, and 10 mm deep. During pressing, the pressing ram was pressed into the cavity under pneumatic pressure.

[0068] The laid and cut fabric of 5 cm×1.5 cm was inserted after a 10-minute warming phase at a tool temperature of 250° C. and hence above the melting temperature of the thermoplastic. The workpiece was pressed in the cavity for 6 minutes at a pressure of 100 bar. During this time, after a solidification phase of 2 minutes, the tool temperature was lowered and the pressed organosheet was removed.

[0069] FIG. 4 shows a photograph in FIG. 4a) and SEM micrographs of the organosheet at different magnifications in FIGS. 4b) and c). The organosheet obtained was investigated by electron microscopy, using a Zeiss Neon 40 scanning electron microscope equipped with EDX detector. SEM micrographs of the sample were obtained by using the InLens detector (secondary electrons) and the SE detector (secondary and backscattered electrons) at an acceleration voltage of 2 kV. The diameter of the glass fiber core was found to be 10 μm, the layer thickness of the thermoplastic sheath 0.9 μm.

[0070] FIG. 4d) shows the EDX spectra of the area denoted in FIG. 4b). The spectrum of the measurement point showed a ratio of the elements carbon, oxygen, and silicon and also fractions of magnesium and aluminum, which agreed with an assumption of 70 to 80 vol % of glass fibers in the organosheet.

EXAMPLE 3

Characterization of the Fiber Volume Contents

[0071] The fiber volume contents of the organosheet were characterized through measurement by thermogravimetric analysis, using a TGA/DSC 1 instrument from Mettler-Toledo AG. Ten samples of the organosheet produced according to example 2, with a weight of 8 mg to 10 mg, were treated thermally at a temperature of up to 700° C. with a heating rate of 7 K/min. At 700° C. the temperature was held for 30 minutes. The weight loss resulting from the carbonization of the matrix was determined at this point. Nine samples out of the ten measured show volume fractions of the glass core of 83 to 86 vol %, based on the total volume.

[0072] The fiber volume content was likewise determined by carbonization of the matrix in a muffle furnace. This was done utilizing samples of 20 g of the organosheets under the same thermal settings (7 K/min heating rate up to a temperature of 700° C. for 30 minutes) as for the TGA. Here as well, the volume fractions of the glass were confirmed at more than 80 vol %.

[0073] All in all, the examples show that organosheets having a high volume fraction of the glass core could be successfully produced.

EXAMPLE 4

Investigation of the Initiator Fraction

[0074] Also investigated was the effect of the photoinitiator on the operating regime. For this purpose, glass fibers were spun on a glass fiber spinning line (LIPEX Anlagentechnik und Handel GmbH) as described in example 2, but with the use as size of monomer systems containing hydroxyethyl acrylate, TEA (triethanolamine) and 1 or 5 mass %, based on the acrylate, of Irgacure® 651. The spun filaments were assembled into fiber and wound using a reel.

[0075] In this case it was found that the drawing speed of the glass fibers in the spinning operation using 5 mass % of initiator was four times higher as compared with the use of 1 mass % of photoinitiator. This shows that the fraction of the photoinitiator had a significant effect on the operating regime.

[0076] The spinning operation was repeated for sizes comprising monomer systems containing hydroxyethyl acrylate, TEA (triethanolamine), and 1 and 5 mass %, based on the acrylate, of Irgacure® 651, in each case at constant spinning speeds of 60 and 120/min. The two-component fiber obtained was subsequently unwound from the reel and pressed to organosheets by hand in a pneumatic press, as described in example 2. The fiber volume contents of the organosheet were characterized by thermogravimetric analysis as described in example 3.

[0077] In this case it emerged that the fraction of plastic in the glass fibers when using 5 mass % of initiator was significantly lower than when using 1 mass % of photoinitiator. The assumption is that there is a relationship between the amount of photoinitiator used and the fraction of plastic which is formed on the glass fiber surface. Without being tied to a theory, it is assumed that the reason for this lies in the exothermic reaction of the polymerization, causing the evaporation temperature of the monomer system to be exceeded. At 5 mass % of photoinitiator, a more exothermic reaction is assumed, resulting in more monomer—which is actually present for forming polymer—being evaporated.

LIST OF REFERENCE NUMERALS

[0078] 1 Bushing (furnace) [0079] 2 Cooling fins [0080] 3 Glass core [0081] 4 Sizing roll [0082] 5 Sizing trough [0083] 6 UV lamp [0084] 7 Aftersizing roll [0085] 8 Sizing trough [0086] 9 Assembling [0087] 10 Thread guide [0088] 11 Reel [0089] 12 Thermoplastic sheath [0090] 13 Glass core [0091] 14 Die [0092] 15 Two-component fiber [0093] 20 Organosheet