Polyurethane composite system having high compressive strength and rigidity

Abstract

The present invention relates to a polyurethane composite system comprising a rigid polyurethane foam and a coating material composed of a compact polyurethane or a compact polyurea, wherein the rigid polyurethane foam comprises a porous three-dimensional reinforcing material which forms a network, where the network encloses at least 50% of the volume of the rigid polyurethane foam, or at least two layers of a porous, at least two-dimensional reinforcing material. The present invention further relates to a process for producing the polyurethane composite system and also a sports article, cladding part or furniture item comprising such a polyurethane composite system.

Claims

1. A polyurethane composite system, comprising: a rigid polyurethane foam; and a coating material comprising a compact polyurethane or a compact polyurea, wherein the rigid polyurethane foam comprises at least two layers of a porous, at least two-dimensional reinforcing material, wherein a maximum distance between two adjacent layers among one another or between an upper layer and an upper side of the foam or between a lower layer and an underside of the foam differs from the minimum distance between two layers among one another or between the upper layer and the upper side of the foam or between the lower layer and the underside of the foam by a factor of not more than 2, wherein the two-dimensional reinforcing material is homogenously distributed in the rigid polyurethane foam, wherein the rigid polyurethane foam has a density of from 30 g/l to 100 g/l, and wherein the rigid polyurethane foam has a density-independent compressive strength of at least 5*10.sup.4 MPa*(l/g).sup.1.6.

2. The system of claim 1, wherein the reinforcing material is a fiberglass mat.

3. The system of claim 1, wherein the rigid polyurethane foam is obtained by a process comprising: (I) mixing a) a polyisocyanate, b) a compound comprising a group which is reactive toward isocyanates, c) a blowing agent comprising water, d) a catalyst mixture comprising a tertiary amine, and optionally e) an further additive, to obtain a reaction mixture; (II) applying the reaction mixture to a reinforcing material; and then (III) curing the reaction mixture.

4. The system of claim 3, wherein the compound (b) comprises a first polyetherol (b1) having a functionality of 4 or more and a viscosity at 25 C. of 10 000 mPas or less, and a second polyetherol (b2) having a functionality of 3.5 or less and a viscosity at 25 C. of 600 mPas or less.

5. The system of claim 4, wherein the compound (b) further comprises a third polyesterol (b3) having a viscosity at 25 C. of 2000 mPas or less, a chain extender (b4), and optionally, a crosslinker (b5).

6. The system of claim 1, wherein the rigid polyurethane foam comprises an isocyanate component comprising PMDI.

7. The system of claim 1, wherein the rigid polyurethane foam has a density-independent compressive E modulus of at least 8*10.sup.3 MPa*(l/g).sup.1.7.

8. The system of claim 1, wherein the coating material is a compact polyurea obtained by mixing a first compound comprising at least two isocyanate groups with a second compound comprising at least two primary or secondary amino groups.

9. A sports article, a vehicle construction part, a cooling container, a wind turbine blade, an aircraft part, a furniture item, or a building industry component comprising: the polyurethane composite system of claim 1.

10. The system of claim 1, wherein the rigid polyurethane foam has a density-independent compressive strength of at least 5.5*10.sup.4 MPa*(l/g).sup.1.6.

11. The system of claim 1, wherein the rigid polyurethane foam has a density-independent compressive E modulus of at least 9.5*10.sup.3 MPa*(l/g).sup.1.7.

12. The system of claim 1, wherein a maximum distance between two adjacent layers among one another or between an upper layer and an upper side of the foam or between a lower layer and an underside of the foam differs from the minimum distance between two layers among one another or between the upper layer and the upper side of the foam or between the lower layer and the underside of the foam by a factor of not more than 1.5.

13. The system of claim 1, wherein the rigid polyurethane foam has a density of from 40 g/l to 60 g/l.

14. The system of claim 1, wherein the rigid polyurethane foam exhibits a combined compressive strength and compressive E-modulus value of from 9.17 to 9.42 MPa.

15. A process for producing the polyurethane composite system of claim 1, the process comprising: coating the rigid polyurethane foam with the compact polyurethane or the compact polyurea.

16. The process of claim 15, wherein the coating comprises spraying a reaction mixture, which produces the compact polyurethane or the compact polyurea, onto the rigid polyurethane foam.

17. A process for producing the polyurethane composite system of claim 1, the process comprising: spraying a first reaction mixture, which produces the compact polyurethane or the compact polyurea onto a part of or an entire surface of a mold; and then adding the reinforcing material and a second reaction mixture, which produces the rigid polyurethane foam, into the mold and reacting the first and second reaction to completion.

Description

(1) The advantages of the invention will be illustrated with the aid of examples:

(2) To produce the rigid foam 1 according to the invention, the polyurethane composite system 2 and the comparative example C1, the polyols used were stirred together with catalysts, stabilizer and blowing agent as per Table 1, subsequently mixed with the isocyanate and the reaction mixture was poured into a box having a base area of 225 mm225 mm and foamed there. To produce the reinforced rigid foams, the reaction mixture was introduced into the same box which now comprised a number of layers of fiberglass mats of the type Unifilo U809-450. The reaction mixture penetrated into the mats and with the foam rising in the box the mats swelled and became distributed homogeneously over the entire height of the foam. A constant foam density of 45 g/l was set by means of the blowing agent. Coating of the rigid foam with a 1 mm thick layer was carried out using the polyurea spray system coating 1 as per Table 2.

(3) Compressive strength and compressive E modulus were measured parallel to the foaming direction in accordance with DIN 53421 at 25 C. The surface hardness was measured using a Tiratest 2602 instrument using a hemispherical indenter having a diameter of 20 mm at 25 C. Here, the force required to press the indenter 10 mm into the test specimen parallel to the foaming direction is measured.

(4) TABLE-US-00001 TABLE 1 Example 1 2 C1 C2 C3 Polyol 1 30 30 30 30 30 Polyol 2 20 20 20 20 20 Polyol 3 30 30 30 30 30 Dipropylene glycol 18 18 18 18 18 Foam stabilizer 2 2 2 2 2 Water 1.8 1.8 1.8 1.8 1.8 Formic acid 1.8 1.8 1.8 1.8 1.8 Dimethylcyclohexylamine 0.3 0.3 0.3 0.3 0.3 Proportion by weight of 10% 10% 0% 0% 0% fiberglass mats Proportion by weight of 0% 0% 0% 10% 10% short fibers (5 cm) Isocyanate 172 172 172 172 172 Coating with coating 1 No Yes No No Yes Compressive strength [MPa] 0.27 0.32 0.22 n.d. n.d. Compressive E modulus 8.9 9.1 5.0 n.d. n.d. [MPa] Surface hardness [N] 290 570 170 200 500 Flexural strength [MPa] 0.56 n.d. n.d. n.d. 0.3

(5) TABLE-US-00002 TABLE 2 Polyetheramine, MW 2000 60 Polyetheramine, MW 400 20 Diethyltoluenediamine 20 MDI-based prepolymer, NCO content 15% 112

(6) The following starting materials were used: Polyol 1: sugar-based polyetherol, OH number=500 mg KOH/g, viscosity=8000 mPas Polyol 2: glycerol-based polyetherol, OH number=400 mg KOH/g, viscosity=350 mPas Polyol 3: polyesterol based on phthalic anhydride/diethylene glycol, OH number=300 mg KOH/g, viscosity=1000 mPas Isocyanate: polymeric methylenedi(phenyl isocyanate) (PMDI), viscosity=200 mPas The viscosity figures relate in each case to the viscosity at 25 C. Stabilizer: silicone-comprising foam stabilizer from Evonik Goldschmidt GmbH

(7) Table 1 shows that rigid polyurethane composite systems according to the invention have high compressive strengths, in particular surface hardness, and high compressive E moduli.