LIGHTFAST POLYURETHANE PREPREGS AND FIBER COMPOSITE ELEMENTS PRODUCED THEREFROM

Abstract

The present invention relates to storage-stable prepregs (preimpregnated fibers) on the basis of lightfast, low-viscous polyurethane systems with an increased characteristic number and flat fiber composite components (molded bodies; composite compounds) produced therefrom, which can be obtained by methods of impregnation of, for example, woven fabrics and laid scrims, and to a method for the production thereof.

Claims

1. A prepreg comprising a sheet-like fiber layer saturated with polyurethane (matrix material) that has not been fully hardened and that has an NCO value of from 3% by weight to 17% by weight (DIN EN ISO 14896:2009-07-method A: method A=NCO value determined by titration), and that has a T.sub.g-value below 40° C. (glass transition temperature T.sub.g measured in accordance with DIN EN ISO 53765-A-20), wherein the polyurethane comprises a reaction product of a reaction mixture comprising: an isocyanate component comprising: A) one or more organic isocyanates selected from the group consisting of: unblocked aliphatic or cycloaliphatic di- and polyisocyanates, polymeric homologs of unblocked aliphatic or cycloaliphatic di- and polyisocyanates, isocyanurates of unblocked aliphatic or cycloaliphatic di- and polyisocyanates, and combinations of any thereof; and a polyol formulation comprising: B) a polyol component made of one or more polyols with a number-average OH number of from 30 to 1000 mg KOH/g, with a number-average functionality of from 1.9 to 2.5; C) one or more dianhydrohexitols; D) one or more latent catalysts which are catalytically active at temperatures of from 50° to 100° C.; and E) optionally auxiliaries and/or additives, other than polyepoxides, wherein the initial viscosity of the reaction mixture at 40° C. is from 2300 to 3200 mPas (measured in accordance with DIN EN ISO 53019), and the ratio of the number of the NCO groups in component A) to the number of the OH groups in component B) is from 1.3:1 to 10:1.

2. A sheet-like fiber-composite component comprising at least one prepreg as claimed in claim 1, wherein the polyurethane has been fully hardened.

3. The sheet-like fiber-composite component as claimed in claim 2, wherein the component further comprises a prepreg layer comprising a sheet-like fiber layer and of a fully hardened polyurethane based on aromatic isocyanates.

4. A process for the production of the prepreg as claimed in claim 1, wherein: i) components B) to D), and optionally E) are mixed at temperatures from 40° to 80° C. to produce a polyol formulation X; ii) the polyol formulation X from i) is mixed with component A) at temperatures from 10° to 80° C. to produce a reactive mixture; and iii) the reactive mixture from ii) is applied to a sheet-like fiber layer and is partially cured.

5. A process for the production of the fiber-composite component as claimed in claim 2, wherein: the one or more prepregs is/are fully hardened at from 110° to 140° C. and at a pressure of from 1 to 100 bar or in vacuo within from 1 to 10 minutes.

6. An article of manufacture comprising the fiber-composite component as claimed in claim 2, wherein the article comprises a sandwich component comprising a core sublayer and an outer layer.

7. A material comprising the article of manufacture of claim 6, wherein the material is selected from the group consisting of a construction material, an aerospace material, a road construction material, a power engineering material, a boatbuilding material, and a shipbuilding material.

8. A bodywork component, an aircraft component, a manhole, a rotor blade of a wind turbine, or a solar reflector comprising article of manufacture of claim 6.

9. The prepreg as claimed in claim 1, wherein the polyol formulation comprises E) the auxiliaries and/or additives, other than polyepoxides.

10. A process for the production of the prepreg as claimed in claim 9, wherein: i) components B) to E) are mixed at temperatures from 40° to 80° C. to produce a polyol formulation X; ii) the polyol formulation X from i) is mixed with component A) at temperatures from 10° to 80° C. to produce a reactive mixture; and iii) the reactive mixture from ii) is applied to a sheet-like fiber layer and is cured.

11. A process for the production of the prepreg as claimed in claim 9, wherein: i) components B) to E) are mixed at temperatures from 50° to 70° C. to produce a polyol formulation X.

12. A process for the production of the prepreg as claimed in claim 4, wherein: i) components B) to D) are mixed at temperatures from 50° to 70° C. to produce a polyol formulation X.

13. A process for the production of the fiber-composite component as claimed in claim 3, wherein: the one or more prepregs is/are fully hardened at from 110° to 140° C. and at a pressure of from 1 to 100 bar or in vacuo within from 1 to 10 minutes.

Description

EXAMPLES

[0063] Storage-stable prepregs made of the systems of the invention, made of unblocked polyisocyanates, polyols, additives, and latent catalysts, were produced and then hardened to give a fiber-composite component, and compared with prepregs/composite components made of polyurethane systems made of internally blocked polyisocyanate and polyol. For the production of the prepreg by impregnation, a thin film of the polyurethane system was applied to the glassfiber textile and distributed on the surface in such a way as to achieve about 55% by weight of glassfiber content, based on the subsequent component. The prepregs were then packed in a vacuum bag and stored at −18° C. The prepregs were removed from the bag and then pressed at 130° C. and 5 bar within a period of five minutes to give a fiber-composite component. Glassfiber content was determined via ashing of the test samples in accordance with DIN EN ISO 1172.

[0064] The NCO/OH ratio gives the ratio of the number of NCO groups in polyisocyanate component A) to the number of OH groups in components B) and C).

Starting Compounds Used:

[0065] Component A): Desmodur® XP 2489 (unblocked polyisocyanate from Bayer MaterialScience AG; mixture of isophorone diisocyanate and hexamethylene 1,6-diisocyanate; NCO content 21% by weight; viscosity at 25° C.: 29 500 mPas)

[0066] Component A′): Desmodur® VP.PU 60RE11 (unblocked polyisocyanate from Bayer MaterialScience AG; mixture of diphenylmethane diisocyanate and polyphenylene polymethylene polyisocyanate; NCO-content 32.6% by weight; viscosity at 25° C.: 20 mPas)

[0067] Component B): linear polyester polyol made of adipic acid, ethylene glycol, and 1,4-butanediol, hydroxy number 86 mg KOH/g and functionality 2, viscosity at 25° C.: 250±50 mPas

[0068] Component C): isosorbide (Addolink® 0312 from Rhein Chemie, hydroxy number 768 mg KOH/g, melting point from 60° C. to 63° C.)

[0069] Component D): Toyocat® DB 40: latent catalyst (blocked amine) from TOSOH Corporation

[0070] Component E): internal release agent Edenor® Ti 05 from Cognis Deutschland, acid number 200 mg KOH/g, functionality 1

[0071] Glassfiber textile: HPT 1040-E0/3AC11, 90°/0° from SGL KÜMPERS GmbH & Co. KG, weight per unit area 1036 g/m.sup.2

Measuring Equipment and Standards Used:

[0072] DSC: DSC Q 20 V24.8 Build 120 from Texas Instruments

[0073] DIN EN ISO 53765-A-20: A-20=determination of glass transition temperature with temperature change 20 kelvins/second

[0074] Gel timer: Gardco GT-SHP-220 from Paul N. Gardner; determination of potlife: this equipment was used to determine the potlife of the resin. The equipment is composed of a stirrer, which is driven by an electric motor. As soon as the maximal torque input in the equipment is reached (the resin then being a high-viscosity or solid material), the motor stops and the gel time can be read from the equipment.

[0075] Viscosimeter: MCR 501 from Anton Paar

[0076] DIN EN ISO 53019 (d/dt=60 1/s): d/dt=shear rate

[0077] DIN EN ISO 14896:2009-07 Method A: Method A=NCO value determination by means of titration

Inventive Example 1

[0078] 10.4 g of component C) were mixed with 20.9 g of component B), 1.5 g of Toyocat® DB 40 and 0.32 g of component E) at 70° C. 59.1 g of Desmodur® XP 2489 were then added at 40° C. and homogenized by a high-speed mixer. A thin film of this mixture was then applied to a glassfiber textile and distributed on the surface, and the material was then stored at −18° C. The NCO value of the prepreg was 11.5% after 24 hours. The prepreg was then pressed at 130° C. and 5 bar to give a fiber-composite component.

Inventive Example 2

[0079] 10.4 g of component C) were mixed with 20.9 g of component B), 1.5 g of Toyocat® DB 40 and 0.32 g of component E) at 70° C. 109.5 g of Desmodur® XP 2489 were then added at 40° C. and homogenized by a high-speed mixer. A thin film of this mixture was then applied to a glassfiber textile and distributed on the surface, and the material was then stored at −18° C. The NCO value of the prepreg was 15.6% after 24 hours. The prepreg was then pressed at 130° C. and 5 bar to give a fiber-composite component.

Comparative Example 3

[0080] 21.3 g of component C) were mixed with 42.5 g of component B), 1.5 g of Toyocat® DB 40, and 0.66 g of component E) at 70° C. 137.5 g of Desmodur® VP.PU 60RE11 were then added room temperature and homogenized by a high-speed mixer. A thin film of this mixture was then applied to a glassfiber textile and distributed on the surface, and then stored at room temperature. The NCO value of the prepreg was 14.8% after 24 hours. The prepreg was then pressed at 130° C. and 5 bar to give a fiber-composite component.

Comparative Example 4

[0081] 21.3 g of component C) were mixed with 42.5 g of component B), 1.5 g of Toyocat® DB 40, and 0.66 g of component E) at 70° C. 75.0 g of Desmodur® VP.PU 60RE11 were then added at room temperature and homogenized by a high-speed mixer. No saturation of glass fibers or production of prepreg was possible because as little as 10 seconds after addition of the isocyanate Desmodur® VP.PU 60RE11 to the mixture of component C, B, D, and E the reaction mixture had completed its hardening.

TABLE-US-00001 TABLE 1 Data from DE-A 10 Inventive Inventive Comparative Comparative 2010029355, Examples example 1 example 2 example 3 example 4 Example NCO/OH equivalent 1.6:1 2.95:1 2.95:1 1.6:1 1:1 ratio Potlife at room 210 min. 216 min. 1 min. 25 10 sec. components in temperature sec. solid form Viscosity at 40° C. about about about not melt not (directly after mixing) in 2800 mPas 3400 mPas 10 mPas measurable, homogeneous, [mPas]; in accordance because solid because melting with after 10 sec point of DIN EN ISO 53019 (d/dt = Fineplus ® 60 1/s) PE 8078 is >60° C. Storage stability of after 7 after 7 after 7 after 2 prepreg [days]; measured days: −29° C. days: −45° C. days: −21° C. days: 50° C. on the basis of glass after 14 after 14 after 14 after 17 transition temperature T.sub.g days: −28° C. days: −45° C. days: −19° C. days: 55° C. in [° C.] in accordance after 21 after 21 after 21 after 30 with DIN EN ISO days: −22° C. days: −45° C. days: −9° C. days: 56° C. 53765-A-20 after 49 after 49 after 49 after 47 days: −17° C. days: −41° C. days: 0° C. days: 55° C. NCO value of prepreg after 1 after 1 after 1 [after . . . days]; measured day: 11.5 day: 15.8 day: 14.8 in accordance with after 7 after 7 after 7 DIN EN ISO 14896: days: 11.3 days: 15.8 days: 13.2 2009-07 method A in [% after 14 after 14 after 14 by wt.] days: 10.7 days: 15.4 days: 12.9 after 21 after 28 after 21 days: 8.2 days: 15.1 days: 12.8 after 35 after 35 after 35 days: 8.1 days: 14.1 days: 12.1 after 49 after 49 after 49 days: 7.1 days: 13.4 days: 11.7 Solidification time of 5 min at 10 min at 2 min at 30 min; during prepreg at elevated 125° C. 125° C. 130° C. this period the temperature temperature is raised from 90° C. to 170° C. Glassfiber content in [% 48 50 55 saturation >50 by wt.] in accordance not possible with DIN EN ISO 1172 Lightfastness of yes yes no no yes polyurethane matrix

[0082] The shelf life of the prepreg was determined both on the basis of the glass transition temperature (T.sub.g) by means of DSC studies and also on the basis of the NCO value [in % by weight]. The values in the table show that the crosslinkability of the prepreg of the invention was not impaired by storage at −18° C. over a period of 7 weeks.

[0083] The solidification time is the time required for full crosslinking of the polyurethane composition, such that no further enthalpy of reaction is detectable for the crosslinking reaction.

[0084] Inventive example 2 shows that potlife is only slightly increased by a higher index.

[0085] In comparative example 3 and 4 the unblocked aliphatic isocyanate Desmodur® XP 2489 used in the system of the invention in inventive example 1 and 2 was replaced by the unblocked aromatic isocyanate Desmodur® VP.PU 60RE11. It was found here that when the equivalent ratio of NCO/OH was 1.6:1 the reaction rate for the aromatic-based system (comparative example 4) is so high that it was impossible to produce prepregs therefrom.