DE10237803A1 - A composite material consisting of isotactic polypropylene reinforcement and matrix with beta-nucleated polypropylene as a matrix component useful in glass- and carbon fiber reinforcement variants - Google Patents

Abstract

A composite material of improved preparation method and increased workability consisting of a reinforcement and a matrix obtained from a matrix forming component, both components in isotactic polypropylene, with beta-nucleated polypropylene as matrix component is new. An Independent claim is included for preparation of a consolidated composite material by melt impregnation of reinforcing fibers from isotactic polypropylene, where a melt of beta-nucleated isotactic polypropylene is used in the matrix.

Description

The invention relates to composite materials, their matrix and reinforcement each consist of isotactic polypropylene, as well as the production such mono-composite materials.

The concept of self-reinforcement sets ahead that the polymer molecules, which is the reinforcement form, oriented in one direction, crystallized and embedded be in a matrix. The matrix can be amorphous or semi-crystalline his. In any case, it is not preferred. The mechanical Distinguish properties such as stiffness from reinforcement and matrix very different properties such as melting or softening temperatures differ only slightly. Generally will Components made of polymers that are in a flowable state. These conditions generally work as described above self-reinforcing Morphology lost.

Therefore, only a few are very special and product-specific manufacturing processes for components made of polypropylene mono-composite materials known.

A. Ajji and N. Legros have published by forming them in the solid phase of polypropylene (PP) products with very good mechanical parameters (A. Ajji and N..Legros: Solid state forming of polypropylene, in "Polypropylene: An A-Z Reference ", Ed .: J. Karger-Kocsis, Kluwer, Dordrecht, 1999, pp.744-751). However, this manufacturing process has the disadvantage that only finished products can be made there a subsequent Forming with a considerable deterioration in the mechanical parameters connected is.

The best self-reinforcement in the melt processing of PP was achieved by using the shear- or stretch flow-induced crystallization (G. Kalay and MJ Bevis: Application of shear-controlled orientation in injection molding of isotactic polypropylene, in "Polypropylene: An AZ Reference" , Ed.:J. Karger-Kocsis, Kluwer, Dordrecht, 1999, pp.38-46; JM Song, M. Prox, A. Weber and GW Ehrenstein: Self-reinforcement of polypropylene, in “Polypropylene: Structure, Blends and Composites ", Ed .: J. Karger-Kocsis, Chapman and Hall, London, 1995, Vol. 1, pp. 273-294). The resulting crystalline superstructure, which is considered a reinforcement, can only be achieved using special processing methods and tools. Here too, shaping processing is not possible, otherwise this special morphology, which determines the mechanical properties, will be lost. Polypropylene is known as the material for fiber production. The reinforcement in a composite material can be carried out by PP fibers if a suitable matrix is found for fixing the fiber or for the tension transmission from the matrix to the reinforcing fiber. Good interfacial adhesion between the matrix and the reinforcing fibers is an essential prerequisite for a composite material with great application potential. This problem was solved by an elegant method namely hot compaction (M.LAbo El-Maaty, DCBassett, RHOlley, PJHine and LM.Ward: The hot compaction of polypropylene fibers, J.Mater.Sci., 31 (1996), 1157-1163 which are respective patents EP 0934145 . US 631 2638 , WO 9815397). In this process, the later matrix is made from the reinforcing fibers themselves. This is done by transferring only the surface of the PP fibers into the melt at precisely set temperatures and very high pressures, thus forming the matrix. The exact observance of the processing conditions requires a very complex process technology. The further processing of semi-finished products is also very problematic due to the very narrow process window. Nevertheless, this problem was solved technically and the respective product was launched on the market by British Petroleum under the brand name Curv ^® (www.curvonline.com - accessed on 08/12/02 at 2:50 p.m.). Although this product has good mechanical characteristics, there is still the disadvantage of difficult further processing.

The very narrow process window could be expanded by mechanically stressing the reinforcing fibers, for example by tensile stress, while their surface is being melted, since the melting temperature of PP is increased under mechanical stress. Loos et al. shown (J.Loos, T.Schimanski, J.Hoffman, T.Peijs and PJLemstra:
Morphological investigations of polypropylene single-fiber reinforced polypropylene model composites, Polymer 42 (2001), 3827-3834). The disadvantage of this method would be that a special and complex process technology would have to be used. The possibilities for further processing of semi-finished products produced with this method would also be severely limited for the reasons set out above.

In order to develop a simple and generally applicable manufacturing and further processing process, it is necessary that the difference between the melting or softening temperatures of the PP matrix and the PP reinforcement is significantly increased. PP grades with different tacticities could be used for this, since they also have different melting or softening temperatures. Isotactic PP has high strength and is used for the production of PP fibers and tapes. Therefore, isotactic PP should be used as a reinforcement material. The matrix material would then be atactic PP, elastomer-like PP (which has atactic and isotactic segments) or syndiotactic PP. The first two variants have the major disadvantage that their strength and rigidity are very low, making them unsuitable for PP mono-composite materials. The third variant is not mixable with isotactic PP. Therefore, their use would have the major disadvantage that the fiber and matrix interfacial adhesion mentioned above is low. It would therefore also be unsuitable for PP mono-composite materials. Furthermore, the immiscibility would restrict the recyclability of the PP mono-composite.

This invention relates to a method a new composite consisting of reinforcements in Form of fibers and ribbons and a matrix, both made of isotactic polypropylene (all polypropylene composite, polypropylene monocomposite, single polypropylene composite), which compared to the prior art easier to manufacture and process are; manufacture. The invention also extends to Manufacturing process of fiber-reinforced composite materials on "pure" PP base. The matrix in this new composite material has it one up to 25 ° C lower melting temperature than the reinforcement. This is achieved that the isotactic PP serving as a matrix by using more or less selective β-nucleating agents into the respective β polymorph (also β phase, β modification called) is implemented and the gain from the original α-polymorph consists.

There are a lot of effective beta nucleating agents which either belongs to the group of quinacridone compounds or are to be classified in the group of the salts of dicarboxylic acids. Varga and Ehrenstein give an excellent overview of the usual β-nucleating agents, including the respective one Patents (J.Varga and G.W. Ehrenstein: Beta modification of isotactic polypropylene, in "Polypropylene: An A-Z Reference ", Ed .: J. Karger- Kocsis, Kluwer, Dordrecht, 1999, pp.51-59).

Take over fibers from isotactic PP the role of reinforcement, because their stiffness and strength by suitable stretching methods by more than ten or twenty times compared to the original one isotactic PP increased can be. The fibers are not only spun and blown from the melt Fibers, possibly with subsequent Cold stretching for use, but also by extrusion stretching manufactured splicing fiber. Other reinforcements besides fibers are ribbons, Stripes and the like.

The composite material can be in consolidated, partially consolidated or non-consolidated form. Consolidated means the reinforcing fibers (Α-isotactic Polypropylene) from the matrix (β-isotactic Polypropylene) completely are wetted. Non-consolidated are those composite variants in which that later β-polypropylene serving as a matrix only partially with the reinforcement (Α-isotactic Polypropylene) in contact comes. It is e.g. as continuous or discontinuous Fibers, ribbons, Stripes etc. Consolidated with unidirectional fiber reinforcement cords and ribbon can preferably summarized by variants of the melt impregnation by Lutz and Harmia (A.Lutz and T.Harmia: Impregnation techniques for fiber bundles and tows, in "Polypropylene: An A-Z Reference", Ed.:J.Karger-Kocsis, Kluwer, Dordrecht, 1999, pp.301-306) become. One more way is that as reinforcement serving fiber made of α-isotactic polypropylene with that from the β modification while merge the melt spinning to achieve such an online compaction. The preferred variant is, however, a bicomponent fiber consisting of α- and ß-isotactic polypropylenes to be produced in situ using the melt spinning process. The cross section of the Bicomponent fiber can be a side / side or preferably one Show shell / core structure. In the case of the shell / core structure the coat made of ß-isotactic Polypropylene and the core made of α-isotactic polypropylene.

For partially and non-consolidated preforms that make up the end product by hot pressing is produced, are particularly suitable in terms of textile technology from blended yarns, consisting of continuous and / or discontinuous fibers from α- and β-isotactic Polypropylene, manufactured systems. These preforms (knitted fabrics, Fabrics, scrims, etc.) can be partially consolidated by hot rolling and thus handling for improve certain applications. Unconsolidated preforms can go through Needling of continuous and / or cut fibers from α- and β-isotactic Polypropylene can be made. Such non-consolidated mats (Felt, fleece, non-woven) with a random orientation of the reinforcing fiber can also produced online using the meltblowing process become.

• – Der Verbundwerkstoff ist einfacher herstellbar und verarbeitbar im Vergleich zum Stand der Technik aufgrund der Tatsache, dass die Schmelztemperatur des Matrixmaterials, also β-isotaktisches Polypropylen, bis zu 25 °C unter derjenigen der zur Verstärkung dienende Faser aus α-isotaktischem Polypropylen liegt.
• – Der Verbundwerkstoff stellt ein „Monomaterial" dar und ist daher besonders für Recycling geeignet.
• – Die verschiedenen Herstellungs- und Verarbeitungsvarianten für Halbzeuge und Fertigprodukte aus diesem neuen Verbundwerkstoff sind Stand der Technik. Daher kann dieser Verbundwerkstoff mit Anlagen aus verschiedenen Bereichen, z.B. Faserhersteller, Textilhersteller, Verarbeiter von Verbundwerkstoffen, verarbeitet werden.
• – Der neue Verbundwerkstoff ist konkurrenzfähig in verschiedenen Anwendungsbereichen zu glass-, natur- und kohlenstofffaserverstärkten Varianten.

The material and method according to the invention have the following main advantages:

• - The composite is easier to manufacture and process compared to the prior art due to the fact that the melting temperature of the matrix material, i.e. β-isotactic polypropylene, is up to 25 ° C below that of the reinforcing fiber made of α-isotactic polypropylene.
• - The composite material is a "mono material" and is therefore particularly suitable for recycling.
• - The various manufacturing and processing variants for semi-finished and finished products made from this new composite material are state of the art. This composite material can therefore be processed with systems from various areas, e.g. fiber manufacturers, textile manufacturers, processors of composite materials.
• - The new composite material is competitive in various areas of application for glass, natural and carbon fiber reinforced variants.

Examples

Example 1: Composites with different reinforcement fiber orientation made from bicomponent fibers with sheath / core or side / side structure

Bicomponent fibers with side / side or core / sheath structure were produced by melt spinning from isotactic polypropylene with (one side or sheath) and without β-nucleating agent. Calcium pimelate (according to Hungarian patent 209132) was used as the β-nucleating agent and was added in 0.1% by weight. This was done in a separate melt extrusion process. The melt index of the polypropylene was 16 dg / min (measured at 230 ° C and 2.16 kg load). The linear density of the fibers produced was 2.2 dtex, which corresponded to a diameter of approximately 18 micrometers. For comparison purposes, fibers were also made from the non-nucleated PP, hereinafter referred to as monofibers. In the bicomponent fibers with side / side structure, the ratio of α- to ß-PP was approx. 1: 1. This ratio was approximately 8: 2 for the fibers with core / sheath structure, ie approximately 20% of the original fiber diameter was converted into matrix during the consolidation. This value is in the range of Curv ^® according to the manufacturer's information (10 to 20% - see Modern Plastics International, 2001, March, pp. 24.26).

Part of the fibers with sheath / core = structure was at 145 ° C with a stretching ratio cold drawn by 8: 1. Both the previously cold drawn as well the untreated fibers were unidirectionally aligned and pressed into laminates with a thickness of approx. 0.5 mm. For consolidation the temperature to 154 ° C and the pressing pressure set to 3 MPa. The one from the laminates taken test specimen were subjected to the tensile load. The determined values of the tensile modulus of elasticity and the tensile strength of laminates made from cold drawn and untreated fibers with side / side or core / sheath structuring are shown in Table 1.

Table 1

The comparative monofiber laminates (manufactured at T = 167 ° C and p = 2.8 MPa pressure) showed an F modulus of 3.2 GPa and one Tensile strength of 88 MPa.

Cut fibers (length 6-8 cm) were made from the bicomponent fibers with a sheath-core structure and a non-woven (fleece, felt) with a basis weight of approx. 200 g / m ^{2 was produced from them} by aerodynamic texturing. For local cohesion and better handling of the nonwoven, the fibers were fixed at certain points by ultrasonic welding. Sheets were pressed from this non-woven with random fiber orientation (T = 154 ° C, p = 3 MPa). For the purpose of comparison, a similar fleece was made from the monofibers and consolidated (T = 167 ° C, p = 4 MPa). The composite material according to the invention showed a tensile strength which was approximately 50% greater and a work absorption which was approximately 250% greater. The work commencement was determined from the areas under the force-strain curves.

Example 2: Composites with random reinforcement fiber alignment made from a needled felt consisting of cut fibers by hot pressing manufactured.

A fleece was made by needling cut splice fibers (linear density: 12 dtex; α = sotactic polypropylene, MFI = 0.8 dg / min; Production: extrusion stretching) and from melt-spun chopped fibers made from β-nucleated poly (propylene-co-ethylene) Block copolymer (β-nucleating agent: γ-quinacridone, Amount of nucleation: 0.001% by weight; linear density of the fiber: 1.8 dtex, Comonomer content: approx. 5% by weight, MFI = 12 dg / min) at a ratio of 4: 1 manufactured. For A similar one was used for comparison purposes Fleece, which melt-spun cut fibers from non-nucleated PP block copolymer (as above) included. Identical were used for hot pressing Conditions as set in example 1. The tensile strength and the penetration resistance in the falling bolt test was for the inventive or the comparison material at 66 or 43 MPa and 10.4 or 5.7 J / mm Plate thickness.

Example 3: Composites with various textile reinforcements made using textiles made from continuous fibers of α-isotactic Polypropylene on the β-isotactic Scattered polypropylene powder before continuous consolidation has been.

One was made by cryogenic grinding fine powder (particle size <0.6 mm) manufactured. It served as a β-nucleating agent NJ-Star NU100 (N ', N'-dicyclohexyl-2,6-naphthalenedicarboxamide - from Ne Japan Chemical Co.). 1 wt.% Of β-nucleating agent was an isotactic PP homopolymer with an MFI value of approx. 80 dg / min metered. This powder was applied to various textiles, namely on fleece, fabric (weave: Atlas) and scrim with unidirectional Fibers (fixation by polyester threads) made from isotactic PP homopolymer scattered and continuously consolidated in-line. This was done on a Double belt press under the following conditions: Heating zone: T = 157 ° C and p = 3 MPa pressure, cooling zone: T = 50 ° C and p = 3 MPa pressure. The relationship reinforcement : Matrix, i.e. α-PP: β-PP, was set to approx. 4: 1. For For comparison purposes, the same spreading method was used with a powder from the original, not β-nukeirtem PP, applied. In these attempts to produce comparative material the temperature of the heating zone was set to T = 167 ° C. The results The mechanical tests are shown in Table 2 below summarized.

Table 2

Example 4: Production of the composite in situ

On a container, blow molded from isotactic polypropylene, a circumferential external reinforcement was made in situ as described below. Oriented tapes of isotactic polypropylene homopolymer (cross section: 0.2 × 5 mm ² ) were smoothed and wound onto the container under tensile stress. At the same time, a melt of β-nucleated poly (propylene-co-ethylene) block copolymer (ethylene content: approx. 10% by weight, MFI = 0.4 dg / min) was fed in to wet the a-PP ribbon in situ to reach. 0.1% by weight of calcium sebazate (Hungarian patent specification 209132) was used as the nucleating agent. A wheel was used for consolidation, which was pressed onto the tapes soaked in the melt. The quality of this external reinforcement was checked in the burst test (pressure medium: water). The burst pressure of the container was 50% higher than that of an unreinforced container. Comparative studies with the non-β-nucleated melt did not improve the bursting resistance.

Non-patent literature cited

A. Ajji and N..Legros: Solid state forming of polypropylene, in "Polypropylene: An A-Z Reference ", Ed .: J. Karger-Kocsis, Kluwer, Dordrecht, 1999, pp.744-751).

G. Kalay and M. J. Bevis: Application of shear-controlled orientation in injection molding of isotactic polypropylene, in "Polypropylene: An A-Z Reference ", Ed .: J. Karger-Kocsis, Kluwer, Dordrecht, 1999, pp. 38-46

JM Song, M. Prox, A. Weber and GW Ehrenstein: Self-reinforcement of polypropylene, in “Polypro pylene: Structure, Blends and Composites ", Ed .: J. Karger-Kocsis, Chapman and Hall, London, 1995, Vol. 1, pp. 273-294

M. I. Abo El-Maaty, D.C. Bassett, R.H. Oleley, P.J. Hine and LM.Ward: The hot compaction of polypropylene fibers, J.Mater.Sci., 31 (1996), pp. 1157-1163

www.curvonline.com - Access on 08/12/02 at 2:50 p.m.

J.Loos, T. Shimanski, J. Hoffman, T. Peijs and P.J. Lemstra: Morphological investigations of polypropylene single-fiber reinforced polypropylene model composites, polymer 42: 3827-3834 (2001)

J.Varga and G.W. Ehrenstein: Beta modification of isotactic polypropylene, in "Polypropylene: An A-Z Reference", Ed .: J. Karger-Kocsis, Kluwer, Dordrecht, 1999, pp. 51-59

A.Lutz and T.Harmia: Impregnation techniques for fiber bundles and tows, in "Polypropylene: An A-Z Reference", Ed .: J. Karger-Kocsis, Kluwer, Dordrecht, 1999, pp.301-306

Modern Plastics International, 2001, March, pp. 24, 26

Claims (9)

Composite material with improved production and processability consisting of a reinforcement and a matrix, or of a matrix-forming component, both made of isotactic polypropylene, characterized in that the matrix or the matrix-forming component is β-nucleated polypropylene. Composite material according to claim 1, characterized in that the matrix or the matrix-forming component is preferred from 0.001 to 1 weight percent beta nucleating agent having. Composite material according to claims 1 to 2, characterized in that that the composite or its preform in consolidated, partially consolidated or non-consolidated form. Method of making the consolidated composite by melt impregnation the reinforcing fiber made of isotactic polypropylene according to claims 1 to 3, characterized in that the melt acting as a matrix is beta-nucleated isotactic Is polypropylene. Method of making the consolidated composite according to claims 1 to 3 by melt impregnation by means of pultrusion of a mixed yarn, which is both reinforcing fiber as well as matrix-forming fiber, characterized in that that the fiber converting to the matrix is β-nucleated isotactic polypropylene is. Method of making the consolidated composite according to claims 1 to 3 by melt impregnation using pultrusion of a fiber bundle consisting of bicomponent fibers, characterized in that the component converting to the matrix of the bicomponent fiber β-nucleated isotactic polypropylene. Process for the production of the non-consolidated composite according to claims 1 to 3 by using melt-spun bicomponent fibers, characterized in that one of the fiber components is beta-nucleated isotactic polypropylene. Process for the production of the non-consolidated composite according to claims 1 to 3 by textile engineering methods of prefabricated continuous and / or discontinuous fibers and ribbons for the reinforcement or for the matrix, characterized in that one of the fibers or ribbons used is beta-nucleated isotactic polypropylene. Process for making a consolidated composite according to claims 1 to 3 by in situ merging of reinforcement and the matrix-forming melt, characterized in that the metered melt a β-nucleated isotactic polypropylene.