FIBER-REINFORCED COMPOSITE MATERIAL HAVING STYRENE (CO)POLYMER AND NATURAL FIBERS

Abstract

A fiber-reinforced composite material (K), containing a thermoplastic polymer matrix and at least one natural-fiber component, is technically advantageous if it contains at least 45% (v/v) of a styrene (co)polymer (A) as polymer matrix, 30-55% (v/v) of a natural-fiber sheet material (B) as natural-fiber component, optionally 0-10% (v/v) of an additional polymer component (C), and optionally 0-10% of at least one additive (D), the volume percentages of components (A) to (D) adding up to 100 volume percent of the composite material (K).

Claims

1-15. (canceled)

16. A fiber-reinforced composite material (K) comprising a thermoplastic polymer matrix and at least one natural fiber component, the composite material (K) containing: at least 45% (v/v) of at least one styrene (co)polymer (A) as polymer matrix; 30-55% (v/v) of at least one natural fiber sheet material (B) as a natural fiber component; optionally 0-10% (v/v) of at least one further polymer component (C) that is different from component (A); and optionally 0-10% (v/v) of at least one additive (D), wherein the volume percentages of components (A) to (D) together add up to 100 percent by volume of the composite material (K).

17. The composite material (K) of claim 16, wherein the natural fiber sheet material (B) is formed from natural fibers selected from the group consisting of: flax fiber, cotton fiber, kenaf fiber, jute fiber, hemp fiber, cellulose fiber, sisal fiber, chitin fiber, keratin fiber, bamboo fiber, and coconut fiber; and/or of pretreated natural fibers selected from the group consisting of: flax fiber, cotton fiber, kenaf fiber, jute fiber, hemp fiber, cellulose fiber, sisal fiber, chitin fiber, keratin fiber, bamboo fiber, and coconut fiber.

18. The composite material (K) of claim 16 or claim 17, containing 45-70% (v/v) of the at least one styrene (co)polymer (A); 32-50% (v/v) of the at least one natural fiber sheet material (B); 0-9% (v/v) of the at least one further polymer component (C) that is different from (A); and 0.05-5% (v/v) of the at least one additive (D).

19. The composite material (K) of claim 16 or claim 17, containing 45-60% (v/v) of the at least one styrene (co)polymer (A); 32-50% (v/v) of the at least one natural fiber sheet material (B); 0-9% (v/v) of the at least one further polymer component (C) that is different from (A); and 0.05-5% (v/v) of the at least one additive (D).

20. The composite material (K) of claim 16 or claim 17, wherein the styrene (co)polymer (A) comprises at least one styrene-acrylonitrile copolymer and/or at least one a-methyl-styrene-acrylonitrile copolymer.

21. The composite material (K) of claim 16 or claim 17, wherein the natural fiber sheet material (B) is a flax fiber sheet material.

22. The composite material (K) of claim 16 or claim 17, wherein the natural fiber sheet material (B) is a fiber fabric having a linear mass density of 100-600 tex.

23. The composite material (K) of claim 16 or claim 17, wherein the natural fiber sheet material (B) is a fiber fabric having a linear mass density of 150-450 tex.

24. The composite material (K) of claim 16 or claim 17, wherein the natural fiber sheet material (B) has a basis weight of 100-600 g/m.sup.2.

25. The composite material (K) of claim 16 or claim 17, wherein the natural fiber sheet material (B) has a basis weight of 150-450 g/m.sup.2.

26. The composite material (K) of claim 16 or claim 17, wherein the at least one additive (D) is a release agent or a lubricant and the at least one additive (D) is used in an amount of from 0.05-5% (v/v), based on the total volume of the composite material.

27. The composite material (K) of claim 16 or claim 17, wherein the composite material (K) has a 20 gloss of at least 40 and a 60 gloss of at least 70, as measured in accordance with the ISO 2813 (2015) standard.

28. The composite material (K) of claim 16 or claim 17, wherein the styrene (co)polymer (A) has a sufficiently high transparency such that the natural fibers of the natural fiber sheet material (B) are visible on the surface of the composite material (K).

29. A process for producing the fiber-reinforced composite material (K) of claim 16 or claim 17, comprising the following steps: a) forming a layer assembly of at least one thermoplastic layer composed of the styrene (co)polymer (A), the optional further polymer component (C).sub.L and/or the optional additive component (D); b) forming a layer assembly of at least one layer of the natural fiber sheet material (B); c) pressing the stacked layer assemblies of the at least one thermoplastic layer and the at least one layer of the natural fiber sheet material (B) in a heated tool at a temperature of 160-240? C. and at a pressure of 15-25 bar to form the fiber-reinforced composite material (K); and d) cooling the fiber-reinforced composite material (K) to a temperature below the glass transition temperature (T.sub.g) of the styrene (co)polymer (A), at a pressure of 15-25 bar.

30. The process of claim 29, wherein: a) the layer assembly of the at least one thermoplastic layer has an average thickness of 0.05-0.75 mm; b) the layer assembly of the at least one layer of the natural fiber fabric (B) has an average thickness of 0.05-0.75 mm; c) the stacked layer assemblies of the at least one thermoplastic layer and the at least one layer of the of natural fiber fabric (B) are pressed in a heated tool at a temperature of 180-230? C. and at a pressure of 15-25 bar to form the fiber-reinforced composite material (K); and d) the fiber-reinforced composite material (K) is cooled to a temperature below the glass transition temperature (T.sub.g) of the styrene (co)polymer (A), at a pressure of 15-25 bar.

31. The process of claim 29 or claim 30, wherein the cooled composite material (K) has an average thickness of <4 mm.

32. A structural element for building components and/or esthetic applications, comprising the composite material (K) of claim 16 or claim 17.

33. A structural element for building components and/or esthetic applications comprising the composite material (K) produced by the process of claim 29 or claim 30.

34. Starting materials for producing shaped articles by a thermoforming process; film materials or coatings; packaging materials; or textile sheet materials or fabrics, comprising the composite material (K) of claim 16 or claim 17.

35. Starting materials for producing shaped articles by a thermoforming process; film materials or coatings; packaging materials; or textile sheet materials or fabrics, comprising the composite material (K) produced by the process of claim 29 or claim 30.

Description

EXAMPLES

[0094] Materials Used

[0095] Two different thermoplastic molding compounds (A1) and (A2) are produced: [0096] A1) SAN copolymer composition containing: [0097] (A1.1) 33.23% by weight of styrene-acrylonitrile copolymer, 22.4-24.4% by weight of acrylonitrile, MVR (220? C./5 kg)=19.0-29.0 cm.sup.3/10 min, Vicat B50=96.0-102.0? C., viscosity=58.0-66.0 cm.sup.3/g [0098] (A1.2) 33.23% by weight of styrene-acrylonitrile copolymer, 25-29% by weight of acrylonitrile, MVR (220? C./10 kg)=80-120 cm.sup.3/10 min [0099] (A1.3) 33.24% by weight of styrene-acrylonitrile-maleic anhydride copolymer, 23.5-26.0% by weight of acrylonitrile, viscosity=61.0-67.5 cm.sup.3/g

[0100] The densities of these styrene-acrylonitrile copolymers are approx. 1.08 g/cm.sup.3. [0101] (A1.4) 0.30% by weight of PETS (pentaerythritol tetrastearate) as release agent, additive having a density of 0.94 g/cm.sup.3. [0102] A2) for comparative example: Polypropylene composition containing: [0103] (A2.1) 94.35% by weight of a PP homo- or copolymer with an MFR (230/2.16) of 80-120 g/10 min, flexural modulus 1550 MPa, Izod (23? C.) 5.5 kJ/m.sup.2, impact copolymer, nu cleated, antistat, Rigidex P 380-H100 (from Ineos Olefins & Polymers), density 0.90 g/cm.sup.3. [0104] (A2.2) 5% by weight of a polar-functionalized polypropylene with grafted maleic anhydride, MFR (190/0.325) 9-13 g/10 min, grafted maleic anhydride 0.17-0.21% by weight, Priex 20093 from Byk [0105] (A2.3) 0.65% by weight of a mold release agent based on glycerol monostearate, additive (Dimodan HP, from Danisco).

[0106] The density of the polypropylene molding compound (A2) is 0.90 g/cm.sup.3.

[0107] The natural fiber component (B) used in the experiments was:

[0108] Flax fiber fabric: flax fiber twill fabric 2/2, basis weight 300 g/m.sup.2, 300 tex yarn in warp and weft, from manufacturer Bcomp (CH); ampliTex Art. No. 5040), density 1.45 g/cm.sup.3.

[0109] Production of the respective fiber-reinforced composite material (K)

[0110] To produce the fiber-reinforced composite materials (K), various layer assemblies composed of a thermoplastic polymer matrix (as a film) and natural fiber components (fiber fabric) were provided in a static hot press (Vogt P400S). The pressing tool was heated to the desired temperature. The respective layers of the composite material underwent pressing under pressure for a period T1 (for example a few seconds). Finally, the tool was cooled for a period T2 (for example a few minutes) and the material was removed.

[0111] In the examples, flax fiber fabric (ampliTex 5040, 300 g/m.sup.2, 300 tex) was used as the natural fiber fabric (B), and, as thermoplastic component (A), SAN copolymer film (150 ?m) in the inventive example (see above) or a PP thermoplastic film (135 ?m) in the comparative example, as characterized above.

[0112] The layers underwent pressing at a temperature of 210? C. under a pressure of 20 bar for a period T1 of 5 s. The tool was then cooled to 60? C. over a period T2 of 25 min at a pressure of 20 bar. The composite material was then removed and investigated mechanically, optically and in respect of its surface.

[0113] The SAN layer in the inventive composite material had (in each case) an average thickness of 0.150 mm.

[0114] The PP layer in the comparative composite material had (in each case) an average thick ness of 0.135 mm. The flax fiber fabric in the inventive composite material had (in each case) an average thickness of 0.207 mm. The flax fiber fabric in the comparative composite material likewise had an average thickness of 0.207 mm.

[0115] Table 1 shows parameters for the fiber-reinforced composite materials (K) produced

TABLE-US-00001 Comparative Example example Layer structure SAN PP Flax Flax SAN PP Flax Flax SAN PP SAN-based [?m] 450 PP-based [?m] 405 Fiber fabric [?m] 414 414 Calculated thickness [?m] 864 819 % (v/v) of thermoplastic matrix 52% 49% % (v/v) of fiber fabric 48% 51%

[0116] The measured total thickness after experimental production was slightly greater than the calculated thickness of the respective composite material. The inventive composite material contained about 45% by weight of polymer matrix and about 55% by weight of fiber fabric. The PP-based composite material contained about 37% by weight of polymer matrix and about 63% by weight of fiber fabric.

[0117] The fiber-reinforced composite materials (K) obtained were investigated mechanically and characterized by gloss measurements in accordance with the ISO 2813 (2015) standard.

[0118] The materials can be mechanically characterized via the impact strength, notched impact strength, etc. The storage stability at various temperatures and humidities can also be comparatively investigated.

[0119] Table 2 shows the results of the gloss measurement for characterization of the fiber-reinforced composite material (K)

TABLE-US-00002 Comparative Example example 60? gloss 89.9 67.9 20? gloss 55.9 23.0

[0120] It was found that the inventive fiber-reinforced composite material (K) with styrene copolymer as thermoplastic polymer matrix (A) can be used in a simple production process to obtain a composite material having low density, good mechanical properties, and also significantly increased gloss (e.g. 20? gloss or 60? gloss).

[0121] This material is also ecologically advantageous, for example it can be readily supplied to a recycling process.

[0122] The shaped articles produced therefrom were esthetically pleasing, mechanically resilient, and readily storable.

[0123] Analogous composite materials can be readily produced in a corresponding manner with other natural fiber fabrics too, especially ones based on cotton fiber, kenaf fiber, jute fiber, hemp fiber, cellulose fiber, sisal fiber, chitin fiber, keratin fiber, bamboo fiber, and coconut fiber and/or from pretreated natural fibers.