DE102013012593A1 - Process for the production of thermoplastic composite components - Google Patents

Abstract

A method is proposed for producing a composite component with a thermoplastic or thermoelastic polymer matrix having a core element, which comprises the following steps:
(A) providing a core element with recesses arranged superficially on the core element;
(b) transferring the core element provided with the surface depressions into a molding tool;
(c) introducing a liquid reaction mixture having a liquid monomer, dimer or oligomer suitable for forming the thermoplastic or thermoelastic polymer matrix of the composite component in the presence of a catalyst and / or activator into the mold, wherein the surface depressions of the core element are infiltrated with the liquid reaction mixture ;
(d) polymerizing the liquid mono-, di- or oligomer to the thermoplastic or thermoelastic polymer matrix; and
(e) removing the composite component from the mold.

Description

The invention relates to a method for producing a composite component with a thermoplastic or thermoelastic polymer matrix having at least one core element.

Such thermoplastic or thermoelastic composite components are widely used, for example, as lightweight components and / or as shock-absorbing parts in the form of body and interior trim parts of vehicles and aircraft, wherein the core element may be, in particular, foam cores. The production of such composite parts is usually done by means of injection molding, wherein the core element is inserted into a mold and behind or overmoulded with the plasticized, molten thermoplastic or thermoelastic polymer. In addition, such composite components can be produced by hot pressing.

On the one hand, a lack of adhesion of the polymer matrix to the respective core element can prove problematic, which is why the polymer used (or the polymer blend used) must be compatible with the core material, otherwise delaminations can occur. In addition, the geometric structure of the core element limits, in particular relatively fine surface structures of the core element run the risk of not or not completely wetted with the plasticized polymer matrix, so that in turn results in the risk of delamination. On the other hand, such surface structures, however, prove to be advantageous in terms of high strength and toughness of generic composite components, because it comes to a positive connection between the core element and the solidified polymer matrix.

Casting processes are also known in the field of processes for processing thermosetting resins into crosslinked polymers, in which core elements, such as foams, and fiber mats are impregnated with reactive resins, in particular epoxy resins, and the resins are cured by means of suitable crosslinking agents to adhere the thermoset polymer matrix form. Such methods are suitable for the production of highly durable and durable, in particular large-sized moldings, such. B. rotor blades for wind turbines and the like ( DE 10 2010 002 131 A1 ). The DE 20 2012 007 340 U1 describes a similar process for the production of thermoset sandwich members, wherein the core member is formed with undercut recesses to provide a component-locking positive fit between the core member and the thermoset-curable resins. The disadvantage, however, is that such thermosetting moldings are less environmentally friendly and in particular poorly recyclable.

The invention has the object of developing a method for producing a composite component with a thermoplastic or thermoelastic polymer matrix having at least one core element in a simple and cost-effective manner to the effect that the aforementioned disadvantages can be at least largely avoided.

• (a) Bereitstellen wenigstens eines Kernelementes mit oberflächig an dem Kernelement angeordneten Vertiefungen;
• (b) Überführen des mit den oberflächigen Vertiefungen versehenen Kernelementes in ein Formwerkzeug;
• (c) Einbringen einer flüssigen Reaktionsmischung mit wenigstens einem zur Bildung der thermoplastischen oder thermoelastischen Polymermatrix des Verbundbauteils geeigneten, flüssigen Monomer, Dimer und/oder Oligomer in Gegenwart wenigstens eines Katalysators und/oder Aktivators in das Formwerkzeug, wobei die oberflächigen Vertiefungen des Kernelementes mit der flüssigen Reaktionsmischung infiltriert werden;
• (d) Polymerisieren des flüssigen Mono-, Di- und/oder Oligomers zu der thermoplastischen oder thermoelastischen Polymermatrix; und
• (e) Entnehmen des Verbundbauteils aus dem Formwerkzeug.

According to the invention, this object is achieved by a method of the type mentioned at the outset, which comprises the following steps:

• (A) providing at least one core element with recesses superficially arranged on the core element;
• (b) transferring the core element provided with the surface depressions into a molding tool;
• (c) introducing into the mold a liquid reaction mixture having at least one liquid monomer, dimer and / or oligomer suitable for forming the thermoplastic or thermoelastic polymer matrix of the composite component in the presence of at least one catalyst and / or activator, wherein the surface depressions of the core element coincide with the liquid reaction mixture are infiltrated;
• (d) polymerizing the liquid mono-, di- and / or oligomer to the thermoplastic or thermoelastic polymer matrix; and
• (e) removing the composite component from the mold.

The inventive method allows the production of durable and stable composite components, which are environmentally friendly and easily recyclable due to their thermoplastic or - in the case of a thermoplastic elastomer - thermoelastic properties, so that they offer especially for relatively short-lived assets. Due to the use of low molecular weight, liquid mono-, di- and / or oligomers instead of a plasticized polymer with long molecular chains and the concomitant, contrast, significantly lower viscosity can also very narrow depressions in the surface of the core element with the reaction mixture wet, after which Polymer is generated in situ by polymerization of mono-, di- and / or oligomers. In this way, a full-surface and in particular positive connection between the core element and the thermoplastic or thermoelastic polymer matrix is achieved. In addition, the flow paths of the only very slightly viscous reaction mixture can be chosen to be significantly longer than in the case of over or overmolding a core element with a plasticized polymer, so that on the one hand the recesses of the core element can be formed very narrow and / or deep to provide a large contact surface between the core element and the polymer matrix, on the other hand, the production of relatively large-sized thermoplastic or thermoelastic molded parts with complex geometry becomes possible. Moreover, because the polymerization of the mono-, di- and / or oligomers occurs at a temperature below the melting temperature of the thermoplastic or thermoelastic polymer produced, the process of the present invention is more energy efficient than conventional thermoplastic processing techniques and the polymer is not susceptible to potentially damaging thermal stress the production of the composite component, so that can achieve improved material properties.

As already indicated, with regard to the production of lightweight but nevertheless stable composite components, it can be provided in an advantageous embodiment that a core element with a material which has a lower density and / or a lower density than the thermoplastic or thermoelastic polymer matrix is used. Preferred examples of such materials for the core elements used include in particular paper, board and composite materials thereof, polymer foam, metal foam, in particular light metal foam, such as aluminum foam or the like, wood and cork, which may have an open-pore structure in addition to the depressions introduced into the core element in a surface, which in turn can be wetted over its entire area with the low-viscosity reaction mixture.

Due to the use of the liquid mono-, di- and / or oligomers, it is possible, in particular, for at least some of the surface depressions of the core element to be formed with a width of less than 2 mm, in particular less than 1 mm, the surface depressions of the core element Furthermore, in the form of grooves and / or holes, in particular with undercut, can be formed in order to ensure a flat, permanent connection of the thermoplastic or thermoelastic polymer matrix to the core element. The geometry of the grooves or holes are practically no limits, the grooves may be configured for example in the form of lines, circles, ellipses, three, four or mehrecks or the holes may have such a cross-sectional shape. The grooves and / or bores may preferably extend substantially over the entire surface of the core element and form a kind of rib structure, in which engages the thermoplastic or thermoelastic polymer matrix of the composite component. The latter represents a mechanical reinforcement of the core material in terms of its strength and rigidity, without appreciably increasing the overall weight of the composite component as a whole.

In principle, any desired thermoplastic or thermoelastic polymers whose mono-, di- or oligomers are present in liquid form or which can be converted into the liquid state by heating and whose viscosity is lower than that of the corresponding state into the molten state are suitable as the matrix polymer of the composite component transferred polymer. By way of example only, methyl methacrylate may be mentioned in this context, which may be polymerized to polymethyl methacrylate (PMMA). In order to further reduce the viscosity of the reaction mixture, it may also be advantageous if the reaction mixture is preheated before being transferred to the mold, in which case mono-, di- and / or oligomers which are solid at room temperature can also be used melted and introduced in the molten state in the mold. As an example suitable at room temperature solid components of the reaction mixture may be mentioned, for example, ε-caprolactam, which may be polymerized to polyamide-6, in particular cast polyamides, such as. B. cast polyamide 6 or cast polyamide 12, have proven to be very easy to process.

In order to moisten the core element as completely as possible with the liquid reaction mixture and to ensure penetration of the same into the surface depressions of the core element, it can be provided in an advantageous embodiment that the mold is subjected to negative pressure at least during the introduction of the reaction mixture.

The invention also provides the possibility that the mold is maintained substantially isothermally at the reaction temperature which, as mentioned above, is less than the melt or thermoplastic processing temperature of the corresponding polymer. In this way, an alternating heating / cooling of the mold is dispensable and can be implemented with a relatively low energy consumption fast cycle times.

In order to ensure a perfect impregnation of the core element and in particular as complete as possible wetting its surface depressions with the liquid reaction mixture may preferably be provided that a reaction mixture having a dynamic viscosity of at most 20 mPas, in particular of at most 15 mPas, preferably of at most 10 mPas, is used. As mentioned above, for this purpose it may be advisable to heat the mono-, di- and / or oligomers used in order to melt them or, if they are already in liquid form, to further reduce their viscosity.

According to an advantageous embodiment of the method according to the invention can be provided that the reaction mixture further added reinforcing fibers and / or fiber structures are inserted into the mold and impregnated by the reaction mixture, again due to the compared to polymer melts significantly low viscosity of the liquid reaction mixture in comparison with conventional thermoplastic processing better wetting of the fibers and consequently a higher strength of the composite component can be achieved. The fibers may be of synthetic origin (for example, glass, carbon, aramid, etc.) or of natural origin (eg, cellulose, wood, hemp, miscanthus, reed, ramie, etc.) , In particular, in this context fiber structures can be locally introduced into the composite component where mechanical reinforcement or stiffening of the component is desired. Alternatively or additionally, fiber structures can preferably be arranged in the surface region of the core element, so that a sandwich-like structure of the composite component results with the best possible adhesion of the polymer matrix to the core element while penetrating the fiber structures in order reliably to prevent delamination even under load.

The method according to the invention is particularly, although not exclusively, suitable for the production of lightweight components and / or shock-absorbing components, in particular in the form of vehicle parts (eg for interior trim parts or body parts and trim parts that contribute to impact protection), aircraft parts (e.g. B. also for interior trim parts) and boat parts (eg for fuselage parts, superstructures, panels, etc.) as well as structural parts for the construction industry including parts of wind turbines.

The invention with reference to an embodiment with reference to the drawings is explained in more detail. Showing:

1 a schematic view of an apparatus for carrying out a method for producing composite components with a thermoplastic or thermoelastic polymer matrix and having at least one core element; and

2 a graph illustrating the dynamic viscosity η [mPas] of a monomer, an activator and a catalyst of an exemplary reaction mixture as a function of temperature T [° C].

In the 1 schematically reproduced device comprises a processing unit A, which, for example, two, each with a stirrer 1 equipped and in particular heatable mixing container 2 in which two components of the reaction mixture are premixed. While component A may be, for example, a mixture of a liquid or a monomer converted by heating to the liquid state with an activator, component B may contain e.g. B. is a mixture of the same monomer with a catalyst. To every mixing container 2 each one dosing unit closes 3 which serves to the two in the mixing container 2 components to be supplied in the desired proportion of a mixing unit B, which in the present embodiment, a mixing head 4 includes. From the mixing unit B, the finished reaction mixture finally enters a molding unit C, which is an evacuable molding tool 5 having a top and a bottom tool.

Embodiment:

By means of in 1 schematically illustrated device was a thermoplastic composite component based on cast polyamide 6 with a core element of polyvinylidene fluoride-based polymer foam (PVDF, trade name: "Zotek NB79" from Zotefoams) with one opposite the cast polyamide 6 lower density (ie with a lower density of the porous polymer foam based on its volume including its pore spaces). For this purpose, the two mixing containers 2 first evacuated and then purged with nitrogen. In each case ε-caprolactam from BASF SE was used as the monomer at about 110 ° C. in the two mixing containers 2 melted and on the one hand to form the "component A" in the in 1 left mixing container 2 with 1.5 to 2.5% by mass of a commercially available activator for cast polyamides (trade name: "Brüggolen C20P" from Brüggemann Chemical), on the other hand with the formation of "component B" in the in 1 right mixing container 2 with 2 to 4.5 Mass .-% of a commercial catalyst for cast polyamides (trade name: "Brüggolen C10" from Brüggemann Chemical). The two components were in the mixing head 4 homogeneously mixed to the finished reaction mixture and immediately into the mold 5 previously filled with the polymer foam core element having grooved depressions superficially incorporated therein so that the reaction mixture infiltrates and infiltrates the depressions thermoplastic polyamide 6 polymerized. In addition, a fibrous structure can be applied to the core element as required, in particular. The mold 5 In this case, for example, it can be kept essentially isothermally at a temperature of about 150 ° C., at which the polymerization takes place and which, however, is significantly lower than the melting temperature of the cast polyamide of about 220 ° C., so that it is also a perfect demolding of the finished Composite component allows.

2 shows the dynamic viscosities of the constituents of the reaction mixture used, which consists primarily of the monomer (ε-caprolactam) and contains the above-mentioned, small amounts of the activator ("Brüggolen C20P") and the catalyst ("Brüggolen C10"). As can be seen, the molten ε-caprolactam as the main constituent of the reaction mixture at the set temperature window in the range between about 110 ° C and about 150 ° C has a very low viscosity of less than 5 mPas (lower curve in 2 ), wherein the viscosity of the entire reaction mixture is not measurably increased by the slightly higher viscosities of the activator (upper curve) and the catalyst (middle curve). Consequently, an infiltration of even very narrow grooves, gaps or holes of the core element can be ensured, which leads to a very intimate and permanent bonding of the thermoplastic or thermoelastic polymer matrix to the core element after polymerization of the mono-, di- and / or oligomers used and untimely Delaminations prevented.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010002131 A1 [0004]
• DE 202012007340 U1 [0004]

Claims (11)

Process for producing a composite component with a thermoplastic or thermoelastic polymer matrix having at least one core element, comprising the following steps: (A) providing at least one core element with recesses superficially arranged on the core element; (b) transferring the core element provided with the surface depressions into a molding tool; (c) introducing into the mold a liquid reaction mixture having at least one liquid monomer, dimer and / or oligomer suitable for forming the thermoplastic or thermoelastic polymer matrix of the composite component in the presence of at least one catalyst and / or activator, wherein the surface depressions of the core element coincide with the liquid reaction mixture are infiltrated; (d) polymerizing the liquid mono-, di- and / or oligomer to the thermoplastic or thermoelastic polymer matrix; and (e) removing the composite component from the mold. A method according to claim 1, characterized in that a core element is used with a material which has a lower density than the thermoplastic or thermoelastic polymer matrix. A method according to claim 1 or 2, characterized in that a core element is used which is at least partially made of at least one material from the group paper, cardboard and composite materials thereof, polymer foam, metal foam, wood and cork. Method according to one of claims 1 to 3, characterized in that at least some of the surface depressions of the core element are formed with a width of less than 2 mm, in particular of less than 1 mm. Method according to one of claims 1 to 4, characterized in that the surface depressions of the core element in the form of grooves and / or bores, in particular with undercut, are formed. Method according to one of claims 1 to 5, characterized in that the reaction mixture is preheated prior to transfer into the mold, wherein in particular at room temperature solid mono-, di- and / or oligomers are melted and introduced in the molten state in the mold. Method according to one of claims 1 to 6, characterized in that the mold is subjected to at least during the introduction of the reaction mixture with negative pressure. Method according to one of claims 1 to 7, characterized in that the mold is maintained substantially isothermally at the reaction temperature. Method according to one of claims 1 to 8, characterized in that a reaction mixture having a dynamic viscosity of at most 20 mPas, in particular of at most 15 mPas, preferably of at most 10 mPas, is used. Method according to one of claims 1 to 9, characterized in that the reaction mixture further added reinforcing fibers and / or fiber structures are inserted into the mold and impregnated by the reaction mixture. Method according to one of claims 1 to 10 for the production of lightweight components and / or shock-absorbing components, in particular in the form of vehicle, aircraft and boat parts and structural parts for the construction industry.

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