Sheetlike semifinished product having a plastic matrix

Abstract

A sheetlike semifinished product comprising a matrix having at least one latent reactive plastics composition which is curable to afford an elastomer, in particular a thermoplastic elastomer, and fibers embedded in the matrix. A process for producing sheetlike semifinished products is further disclosed.

Claims

1. A sheet-like semifinished product comprising: a matrix comprising at least one latently reactive polymer composition comprising polyurethane and a latently reactive isocyanate, which polymer composition is an aqueous dispersion and can be cured to give an elastomer; and continuous fibers embedded in the matrix.

2. The sheet-like semifinished product according to claim 1, wherein the fibers are based on protein, cellulose, synthetic polymers or inorganic substances.

3. The sheet-like semifinished product according to claim 1, wherein the fibers are arranged substantially in a longitudinal extension to a main area of the semifinished product.

4. The sheet-like semifinished product according to claim 1, wherein the fibers are spread.

5. A process for producing sheet-like semifinished products comprising a matrix comprising the step of: embedding of continuous fibers in the matrix comprising at least one latently reactive polymer composition comprising polyurethane and a latently reactive isocyanate, which polymer composition is an aqueous dispersion and can be cured to give an elastomer.

6. The process according to claim 5, wherein the latently reactive polymer composition is cured at a temperature in a range from 60 to 180° C.

7. The process according to claim 5, wherein the fibers are based on protein, cellulose, synthetic polymers or inorganic substances.

8. The process according to claim 5, wherein the fibers are arranged in a longitudinal extension to a main area of the sheet-like semifinished product.

9. The process according to claim 5, wherein the fibers are spread.

10. A sheet-like semifinished product according to claim 1, wherein the latently reactive isocyanate is encapsulated, surface-deactivated or blocked.

11. A sheet-like semifinished product according to claim 1, wherein the polymer composition can be cured to give a thermoplastic elastomer.

12. A sheet-like semifinished product according to claim 1, wherein the continuous fibers embedded in the matrix are oriented unidirectionally.

13. The process according to claim 5, wherein the at least one latently reactive polymer composition is cured to give a thermoplastic elastomer.

14. The process according to claim 5, wherein the latently reactive polymer composition is cured at a temperature in a range from 100 to 140° C.

Description

EXAMPLE 1

(1) Composition of the Dispersion:

(2) Dispercoll® U XP 2702 (from Covestro AG) is an aqueous, anionic dispersion of aliphatic polyurethane. Combining with an aqueous suspension of a deactivated solid isocyanate, Desmodur® LP BUEJ 471 (an IPDI trimer from Covestro AG), gives a latently reactive system having a content of polyurethane and isocyanate of about 60% and water of about 40%.

(3) Fiber spreading to give the sheet-like semifinished product:

(4) The high-performance fibers are spread and impregnated using this dispersion, so that unidirectional high-performance tapes are formed after drying at 45° C. The matrix material in which the fibers are embedded is at this point in time still latently reactive. High-strength and high-stiffness polyethylene fibers, for example Dyneema SK75 1760 dtex, are spread and impregnated at 5 m/min. One layer of this sheet-like semifinished product has, after drying, a mass loading of about 15 g/m.sup.2 with a proportion by volume of fibers of 60% and a proportion by volume of matrix of 40%.

(5) Lamination to give the Textile:

(6) These semifinished products can be laid down to give, for example, 4-layer laminates. The layer structure is preferably symmetrical with fiber orientations of 90°/0°/0°/90° (known as a cross ply). These laminates are consolidated in a vacuum bag at 100 mbar and 110° C. for 10 minutes to give a composite. In this process, the matrix is activated for curing. This textile displays a mass loading of about 60 g/m.sup.2.

(7) Tests:

(8) Customary tests for this type of textiles are:

(9) (1) tear propagation test (known as a “trouser test”) using a method based on DIN EN ISO 13937-2 and (2) T-peel test using a method based on DIN EN ISO 11339. Testing is carried out 24 hours after production of the specimens, with the specimens having been stored at 20° C. and a relative atmospheric humidity of 65%. (1) Tear propagation test: Cuts are made for a distance of 75 mm longitudinally along the middle line of test specimens of 150 mm×50 mm. In a universal testing machine, these test specimens are pulled apart at a test speed of 10 mm/min. The above-described textile fails by delamination at a maximum force of 146 (+/−10) N (number of specimens=3). (2) T-peel test: Test specimens having a length of about 150 mm and a width of 20 mm are cut to size. The initial crack is located between the two layers having a 0° fiber orientation. In a universal testing machine, these test specimens are peeled further apart at a test speed of 50 mm/min. The above-described textile displays T-peel force values of 1.7 (+/−0.6) N/mm (number of specimens=5).

(10) As reference, a comparable textile was produced using a dispersion composition as per the introductory section of this example 1 but without addition of the deactivated solid isocyanate. The tear propagation test under the conditions set forth in section (1) above gives a maximum force of 81 (+/−4) N (number of specimens=3). The T-peel force under the conditions set forth in section (2) above is 1.0 (+/−0.4) N/mm (number of specimens=5).

EXAMPLE 2

(11) Composition of the Dispersion:

(12) The anionic, aqueous polyurethane dispersion Dispercoll® U XP 2702 (from Covestro AG) is formulated with a water-dispersed blocked isocyanate, Trixene Aqua B 201 (a (dimethylpyra-zole-)blocked hexamethylene 1,6-diisocyanate trimer from Lanxess) to give a latently reactive system.

(13) Fiber Impregnation to give the Sheet-Like Semifinished Product:

(14) Unidirectional carbon fiber tapes (mass per unit area 50 g/m.sup.2, from TK-Industries) are impregnated by means of this dispersion using a doctor blade. One layer of this sheet-like semifinished product has, after drying, a mass loading of about 85 g/m.sup.2 with a proportion by volume of fibers of 50% and a proportion by volume of matrix of 50%.

(15) Lamination to give the Textile:

(16) These semifinished products can be laid down to give, for example, 4-layer laminates. The layer structure is preferably symmetrical with fiber orientations of 90°/0°/0°/90° (known as a cross ply). These laminates are consolidated in a vacuum bag at 100 mbar and 160° C. for 30 minutes to give a composite. In this process, the matrix is activated for curing. This textile displays a mass loading of about 340 g/m.sup.2.

(17) Tests:

(18) Testing is carried out 24 hours after production of the specimens, with the specimens having been stored at 20° C. and a relative atmospheric humidity of 65%. The tear propagation test and the T-peel test are carried out under the conditions indicated in example 1. (1) Tear propagation test: The textile of example 2 fails by delamination at a maximum force of 52 (+/−2) N (number of specimens=3). (2) T-peel test: The textile of example 2 displays T-peel force values of 2.7 (+/−0.7) N/mm (number of specimens=5).

(19) For comparison, a textile was produced using a dispersion composition as per the introductory section of this example 2 but without addition of the blocked isocyanate. The tear propagation test under the conditions set forth in section (1) above gives a maximum force of 41 (+/−2) N (number of specimens=3). The T-peel force under the conditions set forth in section (2) above is 1.6 (+/−0.2) N/mm (number of specimens=5).