FIBER-REINFORCEMENT OF FOAM MATERIALS

Abstract

The present invention relates to a molding made of foam, wherein at least one fiber (F) is located partly within the molding, i.e. is surrounded by the foam. The two ends of the respective fiber (F) not surrounded by the foam thus each project from one side of the molding. The foam is produced by polymerization of a reactive mixture (rM) comprising at least one compound having isocyanate-reactive groups, at least one blowing agent and at least one polyisocyanate.

Claims

1.-15. (canceled)

16. A molding made of foam, wherein at least one fiber (F) is with a fiber region (FB2) located inside the molding and surrounded by the foam while a fiber region (FB1) of the fiber (F) projects from a first side of the molding and a fiber region (FB3) of the fiber (F) projects from a second side of the molding, wherein the foam has been produced by polymerization of a reactive mixture (rM) which comprises the following components (A) to (C): (A) at least one compound having isocyanate-reactive groups, wherein at least one compound having isocyanate-reactive groups has a weight-average molecular weight of at least 1700 g/mol, (B) at least one blowing agent and (C) at least one polyisocyanate which comprises 14% to 100% by weight based on the total weight of the at least one polyisocyanate of at least one polyisocyanate prepolymer, wherein the reactive mixture (rM) comprises no further polyisocyanate other than component (C), wherein the component (A) is produced from a compound selected from the group consisting of alcohols, saccharides, sugar alcohols and amines and the component (B) of the reactive mixture (rM) is selected from the group consisting of n-pentane, isopentane, cyclopentane, 1,1,1,3,3-pentafluorobutane, 1,1,1,3,3-pentafluoropropane, 1,1,1,2,3,3,3-heptafluoropropane, water and hydrofluoroolefins and the component (C) has an isocyanate index in the range from 90 to 180.

17. The molding according to claim 16, wherein the component (C) has an isocyanate index in the range from 80 to 150.

18. The molding according to claim 16, wherein i) the surface of at least one side of the molding has at least one depression, the depression being a slot or a hole, and/or ii) the total surface area of the molding is closed to an extent of more than 30%, and/or iii) the foam has a glass transition temperature of at least 80 C.

19. The molding according to claim 16, wherein i) the fiber (F) is a single fiber or a fiber bundle, and/or ii) the fiber (F) is an organic, inorganic, metallic or ceramic fiber or a combination thereof, and/or iii) the fiber (F) is employed in the form of a fiber bundle having a number of individual fibers per bundle of at least 10 in the case of glass fibers and 1000 to 50 000 in the case of carbon fibers, and/or iv) the fiber region (FB1) and the fiber region (FB3) each independently of one another account for 1% to 45% and the fiber region (FB2) accounts for 10% to 98% of the total length of a fiber (F), and/or v) the fiber (F) has been introduced into the foam at an angle of 0 to 60 or of 10 to 70, relative to the thickness direction (d) of the molding, and/or vi) in the molding the first side of the molding from which the fiber region (FB1) of the fiber (F) projects is opposite the second side of the molding from which the fiber region (FB3) of the fiber (F) projects, and/or vii) the molding comprises a multitude of fibers (F) and/or comprises more than 10 fibers (F) or fiber bundles per m.sup.2.

20. A panel comprising at least one molding according to claim 16 and at least one layer (S1).

21. The panel according to claim 20, wherein the layer (S1) comprises at least one resin.

22. The panel according to claim 21, wherein the layer (S1) additionally comprises at least one fibrous material, wherein i) the fibrous material comprises fibers in the form of one or more plies of chopped fibers, nonwovens, non-crimp fabrics, knits and/or wovens, and/or ii) the fibrous material comprises organic, inorganic, metallic or ceramic fibers.

23. The panel according to claim 20, wherein the panel comprises two layers (S1) and the two layers (S1) are each attached at a side of the molding that is opposite the respective other side of the molding.

24. The panel according to claim 20, wherein i) the fiber region (FB1) of the fiber (F) is in partial or complete contact with the first layer (S1), and/or ii) the fiber region (FB3) of the fiber (F) is in partial or complete contact with the second layer (S1), and/or iii) the panel comprises between at least one side of the molding and at least one layer (S1) at least one layer (S2), wherein the layer (S2) is composed of sheetlike fiber materials or polymeric films.

25. The panel according to claim 20, wherein the molding present in the panel comprises at least one side that has not been subjected to mechanical and/or thermal processing.

26. A process for producing a molding according to claim 16, wherein at least one fiber (F) is partially introduced into the foam with the result that the fiber (F) is with the fiber region (FB2) located inside the molding and surrounded by the foam while the fiber region (FB1) of the fiber (F) projects from a first side of the molding and the fiber region (FB3) of the fiber (F) projects from a second side of the molding.

27. The process according to claim 26, wherein the partial introduction of at least one fiber (F) into the foam is effected by sewing-in using a needle, the partial introduction being effected by steps a) to e): a) optionally applying at least one layer (S2) to at least one side of the foam, b) producing one hole per fiber (F) in the foam and optionally in the layer (S2), wherein the hole extends from a first side to a second side of the foam and optionally through the layer (S2), c) providing at least one fiber (F) on the second side of the foam, d) passing a needle from the first side of the foam through the hole to the second side of the foam and optionally passing the needle through the layer (S2), e) securing at least one fiber (F) on the needle on the second side of the foam, and f) returning the needle along with the fiber (F) through the hole, so that the fiber (F) is with the fiber region (FB2) located inside the molding and surrounded by the foam while the fiber region (FB1) of the fiber (F) projects from a first side of the molding or optionally from the layer (S2) and the fiber region (FB3) of the fiber (F) projects from a second side of the molding, optionally performing steps b) and d) simultaneously.

28. The process according to claim 26, wherein the depressions in the molding are introduced into the foam partially or completely before the introduction of at least one fiber (F).

29. A process for producing a panel according to claim 20, wherein the at least one layer (S1) is produced, applied and cured on the molding in the form of a reactive viscous resin, by liquid impregnation methods.

30. A rotor blade for a wind turbine comprising the molding according to claim 16.

Description

EXAMPLES

Production of the Foams:

[0264] The inventive foam was produced by a continuous double belt foaming process. The plant consists of an upper conveyor belt and a lower conveyor belt. The reactive mixture (rM) was continuously injected between a lower carrier material and an upper carrier material via a high-pressure mixing head. The lower carrier material consisted of an aluminum foil and the upper carrier material likewise consisted of an aluminum foil. The reactive mixture (rM) was subsequently expanded and calibrated between the lower conveyor belt and the upper conveyor belt. The obtained foam was cut into sheets. The sheet thickness was 50 mm. The takeoff rate of the belt was 4.5 m/m in at a discharge rate of 18.1 kg/min. Before further tests and reinforcement with the at least one fiber (F) and thus before production of the molding the upper carrier material and the lower carrier material were taken off and the sheets were planed down to 20 mm for further processing.

[0265] The composition of the reactive mixture (rM) of the comparative example V2 and of the inventive example B1 are reported in table 1 as well as the molecular weight of the polyol component (component A)) and the proportion of the prepolymer in the isocyanate component (component B)).

TABLE-US-00001 TABLE 1 Example B1 Comparative example V2 Parts M.sub.w Parts M.sub.w Component by wt. [g/mol] Functionality by wt. [g/mol] Functionality A polyol 1 20 4350 3 polyol 4 56.5 500 4.3 polyol 2 30 530 3.8 polyol 5 20 400 3 polyol 3 37 545 3.9 polyol 6 6 300 4 glycerol 5 92 3 B water 1.3 water 1.9 pentane 14 pentane 7.5 C pMDI 32 pMDI 150 prepolymer 128 D cat 1 0.5 cat 1 0.5 cat 2 0.5 cat 3 3 cat 3 3.8 E stabilizer 2 stabilizer 2 dipropylene 5 134 2 TCPP 15 glycol Cat 1: s-triazine Cat 2: bis(2-dimethylaminoethyl) ether Cat 3: N,N-dimethylcyclohexylamine Stabilizer: Tegostab B 8495 from Evonik Prepolymer: prepolymer of 4,4 mMDI, dipropylene glycol and polypropylene glycol having an NCO content of 22.9% and an average functionality of 2.2 pMDI: mixture of 1,4-diphenylmethane diisocyanate with higher-functional oligomers and isomers (crude MDI) having an NCO content of 31.5% and an average functionality of about 2.7 TCPP: tris-2-chloroisopropyl phosphate

[0266] The properties of the foams are determined as follows: [0267] Density: The density of the pure foams is determined according to ISO 845 (October 2009 version). [0268] Closed-cell content is determined according to DIN EN ISO 4590:2003. [0269] Notched impact strength is determined according to EN ISO 13802:2006. [0270] Shrinkage is emulated close to production using a vacuum infusion setup. Before commencement of the test the sample (dimensions 15015020 mm.sup.3) is clearly marked on the surface at 48 measuring points in a grid of 2 cm with an edge clearance of 1 cm. The thickness is measured at the labelled points with an accuracy of 0.05 mm, and length and width are measured once to s 1 mm and the weight once to 0.1 g. An average is then formed from the thickness measurement. The test setup is effected on a metal plate. Directly below and above the foam/molding a ply of polyester tearoff fabric is applied to ensure uniform distribution of the vacuum pressure. The nylon vacuum film is secured to the metal plate with vacuum sealing tape; connection of the vacuum is effected next to the foam/molding to be tested but directly on the tearoff fabric. Serving as the connection is a PE or PTFE hose on which a nylon, PE or PTFE spiral hose is mounted. The test setup is subsequently placed in a heating cabinet at 120 C. for 4 hours under permanent vacuum. After cooling of the sample the thickness is remeasured at the 48 marked measuring points, the average is formed and compared with the average before the test. The deviation is defined by

[00002]${\mathrm{.Math.}}_t=\frac{\stackrel{\_}{t_1}-\stackrel{\_}{t_2}}{\stackrel{\_}{t_1}}$ [0271] where .sub.t is shrinkage in the thickness direction, t.sub.1 is the average of the thickness [0272] before the test and t.sub.2 is the average of the thickness after the test. [0273] Abrasion is carried out on a pneumatically powered linear drive at a defined speed of 0.2 m/s and a defined pressing force of 10 N for 50 cycles for the inventive foam while only 25 cycles were used for the comparative example on account of the great abrasion. Material removal in mm/as a percentage of the initial thickness is measured. The distance covered per abrasion cycle is 100 mm. The test temperature was 23 C. The material removal of the foam to be tested is determined with respect to a steel sheet having a defined roughness Rz=127 m and also by abrasion against a sheet of the same foam. In both methods only the material removal from the test object and not that from any counterpart (metal sheet, foam sheet) is measured. In order to allow the influence of any anisotropic alignment of the cells to feed into the measurement the film is rotated by 90 in the plane with respect to the steel sheet and also in the abrasion test with respect to itself. Thus four combinations are measured per example.

[0274] The roughness R.sub.z is the average roughness depth, i.e. the arithmetic mean of the individual roughness depths of five adjacent individual measurement sectors. The individual roughness depth Z.sub.i is the distance between two parallels to the average line which within the individual measurement sector touch the roughness profile at the highest and at the lowest point. X describes the extrusion direction in continuous production processes and the block direction having the longer axis in discontinuous processes. By contrast, Y describes the direction transverse to the extrusion direction in continuous production processes and the block direction transverse to the X axis in discontinuous processes. Z is in both processes defined as the rise direction (thickness) of the foam during the process. [0275] Chemical stability is determined qualitatively in a two-stage process. Initially, a block of the foam having edge lengths of 50105 mm.sup.3 is in a test tube half-immersed (25 mm) in the resin and also in the curing agent to be used and left therein for 4 h at 23 C. It is subsequently qualitatively evaluated whether the foam has undergone partial or complete dissolution or whether it was resistant. The second stage is an infusion test of the foam with subsequent curing according to manufacturer's instructions. This test may be combined with the resin absorption test and can thus generate a partly quantitative result. [0276] Resin absorption: For resin absorption, foams are compared after material has been removed from the surface by planing. As well as the resin systems used, the foam slabs and glass non-crimp fabrics, the following auxiliary materials are used: nylon vacuum film, vacuum sealing tape, nylon flow aid, polyolefin separation film, polyester tearoff fabric and PTFE membrane film and polyester absorption fleece. Panels are produced from the moldings by applying fiber-reinforced outer plies by means of vacuum infusion. Applied to each of the top side and the bottom side of the foams are two plies of Quadrax glass non-crimp fabric (roving: E-Glass SE1500, OCV; textile: saertex, isotropic laminate [0/45/90 45 ] of 1200 g/m.sup.2 in each case). For the determination of the resin absorption, a separation film is inserted between the foam and the glass non-crimp fabric, in contrast with the standard production of the panels. In this way, the resin absorption of the pure foam is determinable. The tearoff fabric and the flow aids are attached on either side of the glass non-crimp fabrics. The construction is subsequently equipped with gates for the resin system and gates for the evacuation. Finally, a vacuum film is applied over the entire construction and sealed with sealing tape, and the entire construction is evacuated. The construction is prepared on an electrically heatable table having a glass surface.

[0277] The resin system used is amine-curing epoxy (resin: BASF Baxxores 5400, curing agent: BASF Baxxodur 5440, mixing ratio and further processing as per data sheet). After the mixing of the two components the resin is evacuated at down to 20 mbar for 10 minutes. Infusion onto the pre-temperature-controlled construction is effected at a resin temperature of 23+/2 C. (table temperature: 35 C.). By means of a subsequent temperature ramp of 0.3 K/min from 35 C. to 75 C. and isothermal curing at 75 C. for 6 h, it is possible to produce panels consisting of the moldings and glass fiber-reinforced outer plies.

[0278] At the start, the foams are analyzed according to ISO 845 (October 2009 version), in order to obtain the apparent density of the foam. After curing of the resin system the processed panels are trimmed in order to eliminate excess resin accumulations in the edge regions as a result of imperfectly fitting vacuum film. Subsequently, the outer plies are removed and the foams present are analyzed again by ISO 845. The difference in the densities gives the absolute resin absorption. Multiplication by the thickness of the foam gives the corresponding resin absorption in kg/m.sup.2.

[0279] The resin absorption tests for the reinforced structure were performed analogously. The amount of resin absorbed by the fibers in the foam was determined qualitatively. To this end the thickness and regularity of impregnated previously introduced rovings (E-Glass, OCV, 400 tex) were evaluated. [0280] The pull out resistance/the required force was qualitatively determined by hand by a pullout test of introduced fibers. The rovings (E-glass, OCV, 400 tex) were introduced into the foam orthogonally to the surface by hand with a needle according to EP 1883526. After introduction of the roving via the roving loop the roving was pulled out of the foam manually. The required force was determined qualitatively.
The results of the tests are reported in table

TABLE-US-00002 TABLE 2 Comparative Test Unit Example B1 example V2 Density (ISO 845) [kg/m.sup.3] 45 45 Closed-cell content [%] + + (ISO 4590) Shrinkage (120 C., [%] 3 3 4 h, 0 mbar) Notched impact [J] ++ 0 strength Abrasion against [mm] 1.75 2.57 itself X - X Abrasion against [%] 9 13 itself X - X Abrasion against [mm] 1.74 3.31 itself X - Y Abrasion against [%] 9 16 itself X - Y Abrasion with respect [mm] 4.17 6.49 to steel sheet having Rz = 127 m (steel - X) Abrasion with respect [%] 21 32 to steel sheet having Rz = 127 m (steel - X) Abrasion with respect [mm] 3.91 5.94 to steel sheet having Rz = 127 m (steel - Y) Abrasion with respect [%] 19 29 to steel sheet having Rz = 127 m (steel - Y) Chemical stability [] Withstands infusion Withstands process infusion process General resin [g/m.sup.2] 250 390 absorption Resin absorption with [g/m.sup.2] low moderate reinforcing structure Pullout resistance [N] high moderate

[0281] The advantages of the inventive foam are apparent from the measured data. The abrasion resistance is markedly increased, thus reducing emission and improving transportability/handling. In addition the foam with reinforcing structures exhibits lower resin absorptions (less weight for same performance) and higher pullout resistances (important for handling and for converting steps).