EP3365148A2

EP3365148A2 - Production of complex hollow foam or sandwich structures by means of a mold core

Info

Publication number: EP3365148A2
Application number: EP16784464.6A
Authority: EP
Inventors: Arnim Kraatz; Denis HOLLEYN
Original assignee: Evonik Roehm GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2015-10-22
Filing date: 2016-10-17
Publication date: 2018-08-29
Also published as: US10919198B2; WO2017067867A2; CN108136624A; HK1256005A1; EP3159129A1; WO2017067867A3; US20180311869A1

Abstract

The invention relates to a method for producing complex foam-molded rigid foam materials, in particular poly(meth)acrylimide (P(M)I) cores, preferably polymethacrylimide (PMI) cores, which can be used in automotive or aircraft construction, for example. The method is characterized in that the use of a particulate core during the foaming process allows for an additional weight reduction in comparison with prior art foam materials or sandwich materials.

Description

Production of complex foam or sandwich structures by means of a mold core

Field of the invention

The invention relates to a process for the preparation of complex, foam-molded

Hard foam materials, in particular poly (meth) acrylimide (P (M) I), preferably from

Polymethacrylimide (PMI) cores, which can be used for example in the automotive or aircraft industry. The method is characterized by the fact that by using a particulate core during foaming, an additional weight saving compared to foam materials or sandwich materials of the prior art can be realized.

State of the art

For many light construction applications, core materials based on

Used rigid foams. These are in most cases coated with cover layers of e.g.

Carbon fiber or glass fiber reinforced composite materials, metals or wood connected and built a sandwich component. Sandwich components in many cases provide the best balance between weight and mechanical properties. For very large volume components, such as e.g. in complex three-dimensional structures with large thickness, or depending on the present

Claim of the component, but it may be that the Kernamterial is not completely needed in the final application. In these cases, it primarily serves as a production aid, which unnecessarily adds additional weight in the final component.

For the production of fiber composite hollow structures, wax cores are used today in small quantities. Here, fiber composite materials are applied to wax cores, consolidated in various infusion procedures and finally removed from the wax core. However, because of the wax cores, the processing methods are limited to low temperatures and low pressures and removal of the wax core has proven to be a very complex process step. This results in only very long cycle times during processing. Thus, only very small quantities can be realized. For the production of foams with a cavity, such a method is not suitable. Thus, a melting within a foam core is excluded due to the diffusion into the pores alone. Alternatively, the wax core would have to be removed over a large-area recess, which in turn would lead to a reduced stability of the foam core.

An overview of the production of P (M) l foam materials or sandwich materials is given below. These processes are easily transferred to other rigid foams, such as PE, PP, PU, PET or PVC foams.

DE 27 26 260 describes the preparation of poly (meth) acrylimide foams (P (M) I foams).

described, which have excellent mechanical properties even at high temperatures. The production of the foams is carried out by casting, ie the monomers and required additives are mixed and polymerized in a chamber. The polymer is foamed by heating in a second step. This process is very complicated and difficult to automate. DE 3 630 930 describes another process for foaming the abovementioned copolymer plates of methacrylic acid and methacrylonitrile. Here, the polymer plates with the help of a

Microwave field foamed, which is why this is referred to below as the microwave method. It should be noted that the plate to be foamed, or at least its surface, must first be heated to or above the softening point of the material. Since the foaming of the material softened by the external heating naturally also starts under these conditions, the foaming process can not be controlled solely by the influence of a microwave field, but must also be controlled by an accompanying heating from the outside. Thus, a microwave field is added to the normal single-stage hot air process to accelerate the foaming. However, the microwave method has proved to be too complicated and therefore not relevant to practice and is still not used.

In addition to PMI foams, foams based on methacrylic acid and acrylonitrile (P-foams) are also known with similar properties. These are described, for example, in CN 100420702C. However, these foams are also produced by means of plates.

Apart from these processes, which start from a non-foamed polymer plate, so-called in-mold-foaming processes, starting from a granulate, are also known. Compared to the described methods, however, these have in principle several disadvantages. Thus, only an uneven pore structure that differs between the interior of the original particles and the interfaces between the original particles is achieved. Furthermore, the density of the foam due to the uneven distribution of the particles during foaming - as described above - additionally inhomogeneous. Furthermore, one can observe this granulated products foamed a poorer cohesion at the interfaces that form between the original particles during foaming, and thus compared to foamed from a semi-finished sheet materials poorer mechanical properties.

In WO 2013/05947 an in-mold process is described, in which at least the latter problem has been solved in that before the particles are filled into the shaping foaming tool, the particles are mixed with a bonding agent, e.g. coated with a polyamide or a polymethacrylate. This achieves a very good grain boundary adhesion. The uneven pore distribution in the final product is not avoided by this method.

However, in-mold foaming has hardly been described for rigid foams, in particular for P (M) I foams to date. For other foam materials, however, such methods have long been known. Thus, polyurethane foams from a corresponding reactive liquid are usually at

Room temperature produced. Foams made of PE, PP, polystyrene or polylactic acid (PLA) are produced from a granulate in an in-mold-foaming process. German Patent Application No. 102014209425.9 discloses a process in which a P (M) I granulate is thermally foamed in a two-shell pressing tool with contour-following cavities, by means of which both heated and cooled are heated. This method is compared to the prior art, a significant increase in efficiency. However, since both heated in the same tool and thus foamed, as well as cooled, the Werkzeugbelegzeit and thus the production cycle is still relatively long. Furthermore, due to

Temperature gradients within the material to be foamed from outside to inside still detectable density gradients in the produced foam core.

task

Against the background of the prior art discussed, it was therefore an object of the present invention to provide a novel process, with which large-volume, complex-shaped

Hard foam cores or sandwich components with respect to the prior art reduced final weight, using the already established manufacturing processes of the components, can be realized. In particular, it was an object of the present invention by means of this method can be processed easily and at high throughput speed hard foam, in particular P (M) I particles in an in-mold-foaming process to molded foam cores or sandwich materials, these compared to the state The technique should also have a significantly reduced weight.

In addition, it was an object of the present invention to provide a process for the in-mold foaming of P (M) I, which leads to end products with an internal cavity and at the same time a very uniform density distribution and narrow pore size distribution within the foam.

In particular, the object was that this method can be carried out in comparison with prior art methods with short cycle times and already without any special reworking

Hard foam cores in the final geometry leads. Other, not explicitly discussed at this point, tasks may arise from the prior art, the description, the claims or the embodiments.

In the context of the present text, the term poly (meth) acrylimide (P (M) I) polymethacrylimides, polyacrylimides or mixtures thereof are understood. The same applies to the corresponding monomers such as (meth) acrylimide or (meth) acrylic acid. Thus, for example, the term (meth) acrylic acid is understood to mean both methacrylic acid and acrylic acid and mixtures of these two. Solution The stated objects are achieved by providing a novel process for the production of complex foam cores, which are particularly preferably

Poly (meth) acrylimide (P (M) I) foam cores. The term rigid foam core generically comprises foam bodies without cover layers, but in particular not necessarily

Rigid foams, and foam cores, in composite or sandwich materials. This method according to the invention comprises the following method steps:

a. Producing a particle filled, made of a film. Filler core, b. Insert the filler core into a tool and then close the tool, c. Charging pre- or unfoamed matrix particles in the cavity between the

Filling core and the inner wall of the tool, d. Foaming the matrix particles, opening the tool and removing the

Hard foam core, e. optional opening of the film at the accessible former contact area from process step b. and f. Removal of the particles from the hard foam core.

In particular, the insertion of the filling core in step b. There are different variants that affect the overall process. The three most important variants are the following:

In a first variant of the filling core in step b. inserted into the tool so that the filling core between 0.5 and 10, preferably 1 to 5 area percent of the inner wall of the tool touches. The opening, for example, can be hung simply. In this variant, as a rule, process step e is omitted. and the removal of the particles in process step f. is easiest.

In a second variant of the filling core in step b. inserted in such a way that the filling core after process step d. completely surrounded by the foam. This can be done by the filler core

for example, be hung on a thread in the tool. In this variant of the present

Invention is the foam in step e. partially drilled or cut open. This is done to the particles in step f. then remove. The result is a foam body whose cavity can be almost completely surrounded by the foam. The size of the subsequent opening depends on the particle size and the flowability, as well as possibly the shape of the cavity and the desired removal time of the particles. In a third variant of the method according to the invention, the filling core in method step b. inserted so that the filling core between 0.5 and 10, preferably 1 to 5 area percent of

Touched inside wall of the tool. In addition, this site is with an easy to remove

Device closed. This may be, for example, a plug or a clamp. This device is finally in step e. away. Optionally, the device can be used again after the removal of the particles and thereby fixed, for example by means of gluing or sewing.

For method steps a. and b .: With regard to the particles, they are to be selected such that they remain free-flowing up to a temperature which corresponds to the maximum foaming temperature used. In this case, flowable means that they are produced using only low mechanical energy, such as

Shaking, bumping or poking, can be put back into a free-flowing state.

The particles are preferably chemically stable under prolonged loading under said foaming temperature and overpressure, undergo only a slight change in volume and do not melt or stick together.

Particularly suitable particles are sand, at the foaming temperature stable and solid polymer particles, e.g. made of PEEK, metal particles or glass beads. Conceivable, however, are other especially mineral fillers or temperature-stable seeds.

According to the invention, the film should likewise be an analogue temperature-stable film. Examples include PTFE, PEEK or PPSU film. It is also conceivable, e.g. to use silicone or metal coated or impregnated film. In the latter, it can be as

Carrier material also act on a tissue or paper, which has been coated or impregnated.

The filling core is preferably in a tightly packed and thus dimensionally stable form. The filling can be done for example by means of compressed air or suction under vacuum. For compression, pressure can additionally be applied to the outside, for example in a press. Optionally, a shaping of the filling core can also take place. The shaping can also be carried out or supported by the underpressure and / or overpressure. After filling, the film can either be closed to a closed bag or remain open at the filling point and introduced with this pointing upwards into the tool. Preferably, the filling core is open at one point and is at this open point in step b. hung in the tool.

In a particular embodiment of the above-mentioned first or third variant of the filling core in step b. inserted into the tool so that it touches the inner wall of the tool in at least two places. The second position, which does not point upwards within the movement, is forcibly closed. In such a procedure, it is then possible in

Process step f. to blow the particles out of the cavity by means of compressed air. For this purpose, the second or the second accessible on the surface of the hard foam core point must be opened. For process steps c. and d .: in principle, all known processes for the production of particle foams can be integrated into the process according to the invention. As a particularly preferred, it has a method in which the actual foaming takes place while relaxing the tool interior, has been found. Such a method is for example for P (M) I in the international application

PCT / EP2015 / 064316. In addition, this method is briefly described as an exemplary embodiment of the method steps c. and d. of the present method. It is clear to the person skilled in the art that as stated, other particle foams and / or other particle foaming processes in process steps c. and d. can be applied. Therefore, the following statements should be considered as a preferred embodiment of the method according to the invention:

In such a preferred foam partial process, the matrix particles are produced in a process step cO. preheated and filled under pressure in the tool. Foaming then takes place at the foaming temperature by lowering the pressure.

The process steps c. and d. in this embodiment have the following individual steps: cO: heating of matrix particles to a normal pressure foaming temperature Ti, this taking place under a pressure pi at which a volume nominal of the P (M) I particles of not more than 10% by volume takes place in 10 minutes, c1: filling of the matrix particles into the cavity formed by filler core and tool inside, wherein the filling takes place at a pressure p2, which is preferably at most 10% less than pi, and

then closing the tool, d1: relieving the tool cavity to a pressure p3 at a temperature T2, foaming of the particles takes place, d2: cooling the tool cavity to a temperature T3 and d3: opening and removal of the hard foam core. A particular advantage of this embodiment is that the foaming can be carried out within at most 2 min, and that the method steps a. to d. can be performed together within a short period of 5 to 45 minutes, wherein method step a. can be performed in parallel to the other process steps.

Another advantage is the even temperature distribution within the material at the moment of foaming. This leads to a particularly uniform distribution and size distribution of

Pores in the final product. Thus, the end product has no or only minimal density gradients compared with foams of the prior art. In foams of the prior art, the outer regions are generally more foamy than inner regions. The temperature Ti is preferably between 150 and 250 ° C., more preferably between 180 and 220 ° C. Pressure pi in process step cO. and pressure p2 in step c1. are preferably between 2 and 20 bar. Temperature T2 is preferably set to a value between 150 and 250 ° C, particularly preferably between 180 and 220 ° C. The pressure p3 is preferably between 0, 1 and 2.0 bar, more preferably between atmospheric pressure and 1, 5 bar.

In a particular variant of the method according to the invention, method step c1. before process step cO. carried out. In this variant, the preheating of the particles takes place in the

Tool in which in step d. also foamed. In this variant, the pressure P2 is flexibly selectable and it can e.g. be filled at atmospheric pressure. Preferred over this variant, however, is an embodiment of the method according to the invention, in the method step cO. before method step c1. is carried out.

In this embodiment, it is particularly preferred that the particles in process step cO. to store in a reservoir at temperature Ti and the pressure pi and thus preheat. The particles are then batchwise in process step c1. filled in the tool, wherein after the batchwise filling in each case the connection between the reservoir and the tool is closed before the relaxation in step d1. he follows.

As particularly favorable, it has been found, the matrix particles prior to addition in step c1. in the reservoir at a temperature less than 50 ° C below the

Foaming temperature is, and stored at a pressure which is at least 1 bar above normal pressure, and are filled batchwise in step c1 in the tool, wherein after the batchwise filling in each case the connection between the reservoir and the tool is closed.

Additionally or alternatively, it has proven to be very advantageous and accelerating the process, the particles in step c1. into the cavity within the tool to suck and / or blow.

The pressure P2 in method step c1. this results from the pressure in the particle template, such as e.g. a reservoir, the blank pressure of the tool and the pressure changes resulting from suction or blowing devices. In the configuration of the parameters for method step c1. According to the invention, care should be taken that all these parameters are set so that P2 is at most 10% below pi or even above pi. This will be too fast

Foaming of the particles prevented.

In addition, it is in step c1. advantageous to fill the tool to a level between 50 and 100%, preferably between 75 and 98% with particles. 100% level in this context means that the tool is filled up to the top edge with the particles. Of course, between the particles remain free spaces whose size depends on the particle size and particle shape. Theoretically, these clearances can also make up a level of 100% up to 50% of the interior of the tool. In process step c. These free spaces are finally closed by the foaming, so that a homogeneous hard foam core is formed. Before process step b. In addition to the filling core, the interior of the tool can be equipped with so-called inserts. These are when filling the granules in step c. initially surrounded by this and thereby completely or partially enclosed in the later hard foam core as an integral part of this workpiece of the foam matrix. These inserts may be, for example, articles with an internal thread. By means of this internal thread, the rigid foam cores can be screwed later. Analog can also bolts, hooks, pipes or the like can be installed. It is also possible to integrate electrochips or cables already in the production of the hard foam core in this.

Regarding in step c. According to the invention, there are various preferred embodiments of matrix particles used.

In a first embodiment, the matrix particles are a ground material made of a rigid foam, in particular P (M) 1 plate polymer, which is obtained as a cast polymer. These plates can be comminuted, for example in a mill to suitable particles. Milled matrix particles are preferably used in this variant with a particle size between 1, 0 and 4.0 mm.

In a preferred variant of the invention, these matrix particles are prefoamed before they are melted in process step c. be filled in the tool. It is important to ensure that the pre-foaming is not complete, but only up to a Schäu ment degree between 10 and 90%, preferably between 20 and 80% is performed. The final foaming then takes place in process step d.

Pre-expanded matrix particles are preferably used in this variant with a particle size between 1, 0 and 25.0 mm. The prefoamed matrix particles preferably have a density between 40 and 400 kg / m ³ , preferably between 50 and 300 kg / m ³ , more preferably between 60 and 220 kg / m ³ and especially preferably between 80 and 220 kg / m ³ . A particularly suitable process for prefoaming P (M) I is described, for example, in German Patent Application No. 102013225132.7.

In a third embodiment of the process, the matrix particles are hard foam, preferably P (M) 1 suspension polymers. Such suspension polymers are preferably used with a particle size between 0, 1 and 1, 5 mm, more preferably between 0.1 and 1, 0 mm. The preparation of P (M) l suspension polymers can be read, for example, in the international application with the file reference PCT / EP2014 / 050658.

In a fourth embodiment of the method according to the invention are prefoamed

Suspension polymers in process step c. used. With regard to the degree of foaming, the same applies as described above for the prefoamed matrix particles of a millbase. The prefoamed matrix particles preferably have a density between 40 and 400 kg / m ³ , preferably between 50 and 300 kg / m ³ , more preferably between 60 and 220 kg / m ³ and especially preferably between 80 and 220 kg / m ³ . Such prefoamed suspension polymers are preferably used with a particle size between 0, 1 and 2.0 mm, more preferably between 0.2 and 1.5 mm. Optionally, in the process according to the invention during the first half, preferably during the first quarter of the process duration of process step d. Hot air, a hot gas or steam, preferably a hot inert gas or air, are conducted into the interior of the tool. This introduction has a temperature between 90 and 300 ° C, preferably between 150 and 250 ° C.

Compared to other prior art, moldings or foam materials with a significantly more homogeneous pore structure and without defects and at the same time in more complex forms can be produced by means of a process based on flash-foaming. Furthermore, it is possible with this method to produce these complex shapes quickly, in short cycle times and with particularly good quality. In particular, the method according to the invention has shortened heating and cooling cycles compared to prior art methods. Furthermore, the present method has the great advantage over the prior art that it is so gentle that the surface of the matrix particles is not damaged.

In a particular embodiment of the method according to the invention, it is possible, the inner sides of the tool shells before step b. or c. with a material, which is a later

Cover layer forms, preferably interpreted with prepregs or organic sheets. It is also possible, for example, to bring decorative films or metals. The films, metals, prepregs or organ sheets may optionally be coated with an adhesive or a primer. When foaming in process step d. The resulting foam then combines with the coated or

uncoated foils, metals, prepregs or organic sheets, which thus form cover layers. By means of such a procedure, the hard foam core in process step d. taken in the form of a composite material with cover layers.

Alternatively or additionally, also the outside of the filling core before process step b. or c. with an analogous material which forms a subsequent top layer, preferably with prepregs or organo sheets, are occupied.

The phrase "forming a later topcoat" means preferably that it is an organo sheet or prepreg which cures in parallel under the foaming conditions.

To process steps e. and f. the following aspects are shown:

If the filler core is completely closed, it must be opened at one or more points accessible on the outside of the material. The removal of the particles in process step f. In the simplest case, this is done by simply pouring it out, whereby the particles can usually be reused afterwards. Under certain circumstances, it is in method step f. necessary, removal e.g. by shaking, blowing, poking or hitting.

Optionally and above all as a function of the film material and the geometry of the cavity, after method step f. the foil is pulled out of the hard foam core. Should not be possible or desired, it can also remain within the cavity without significant weight contribution.

In addition, in order to improve the adhesion between the foam core material and cover layers, which plays a role in later process steps for the production of composite materials,

Adhesion promoters are used. As an alternative to application in a later method step, these adhesion promoters may also be applied to the surface of the matrix particles even before the prefoaming according to the invention. In particular, polyamides or poly (meth) acrylates have proven to be suitable as adhesion promoters. However, it is also possible to use low molecular weight compounds which result from the preparation of composite materials, in particular depending on the type used

Matrix material of the cover layer, known in the art, can be used.

In particular, the method according to the invention has the great advantage that it can be carried out very quickly and thus in combination with follow-up processes with very short cycle times. Thus, the inventive method can be very well integrated in a series production.

For the entire process according to the invention, the process parameters to be selected depend on the design of the system used in the individual case and its design, as well as the materials used. They can easily be determined by a few preliminary tests for the expert.

According to the invention, it is also possible to store the intermediate product after process step d., Containing the filler core, and / or initially to further refining steps, such as e.g. a bonding,

Install, cover with topcoats, polish, cut or saw. The particles from the filling core can then in the process steps e. and f. optionally be removed afterwards. This additionally stabilizes the foam material during further processing or storage.

The material used according to the invention is preferably P (M) I, in particular PMI. Such P (M) I foams are characterized by a special strength. The P (M) I foams are normally produced in a two-stage process: a) production of a cast polymer and b) optional partial foaming of this cast polymer. According to the prior art, these are then cut or sawn into the desired shape. An alternative which is even less technically established is the executed in-mold foaming for which the method according to the invention can be used. For the preparation of P (M) I first monomer mixtures, which (meth) acrylic acid and

(Meth) acrylonitrile, preferably in a molar ratio of between 2: 3 and 3: 2, contained as main components. In addition, other comonomers may be used, such as e.g. Esters of acrylic or methacrylic acid, styrene, maleic acid or itaconic acid or their anhydrides or

Vinylpyrrolidone. However, the proportion of the comonomers should not be more than 30% by weight. Small amounts of crosslinking monomers, such as allyl acrylate, may also be used. However, the amounts should preferably be at most 0.05% by weight to 2.0% by weight. The copolymerization mixture further contains blowing agents which either decompose or vaporize at temperatures of about 150 to 250 ° C to form a gaseous phase. The polymerization takes place below this temperature, so that the cast polymer contains a latent blowing agent. The polymerization suitably takes place in block form between two glass plates. The production of such PMI semi-finished products is in principle known to the person skilled in the art and can

for example, in EP 1 444 293, EP 1 678 244 or WO 201 1/138060. As PMI semi-finished products are in particular those mentioned, which are sold in foamed form under the product name ROHACELL ^® by the company Evonik Industries AG. Regarding manufacture and

Processing are to be regarded as analogues to the PMI foams Acrylimid semi-finished products (Pl semi-finished products). For toxicological reasons, however, these are much less preferred than other foam materials.

In a second variant of the process according to the invention, the P (M) I particles are a suspension polymer which, as such, can be introduced directly into the process. The preparation of such suspension polymers can be described, for example, in DE 18 17 156 or in WO

2014/124774 be read.

As an alternative to P (M) I, however, it is also possible according to the invention to use other foams, in particular

Hard foams, such as PP, PET, PE, PVC or hard PU foams can be used. An adaptation of the process to these foams takes place via the respectively specifically required process parameters during foaming and are easy to deduce for the skilled person. The foam body according to the invention or a foam core containing

Sandwich materials are as it were part of the present invention and are characterized in particular by the fact that they are at least in one place with the surface of the

Foam core associated cavity. This point preferably makes up between 1 and 10 area percent of the surface. Optionally, this point can then be closed with a cover material by means of gluing, sewing, pinning or bolting. Also can be a prepreg or

Organ sheet placed and cured. Furthermore, these are optional with the previously

provided inserts.

Furthermore, these foam bodies or foam cores have between the inner surface of the foam and the cavity a film, a cured prepreg or organo sheet or nothing at all. These are preferably P (M) I rigid foam cores in sandwich materials or in order

P (M) I-foam body.

The hard foam core may preferably have a complex shape. The surface of a

Foam body according to the invention is at least 95% of one of the

Hard foam material existing, preferably a thickness of at least 100 μιτι having skin is enclosed. This means that these new foam foam cores or bodies are not open

Have pores on the surface and thus over the materials of the prior art without an additional cover layer on a particular stability, for example against shocks or blows have. These materials, taken alone and thus independent of the process according to the invention, are novel and thus likewise part of the present invention.

These novel rigid foam cores preferably have a density of between 20 and 180 kg / m ³ . This density specification refers to a hollow foam body including cavity, whose opening is closed real or fictitious.

The foamed foams produced according to the invention can be further processed, for example, into foam core composite materials. The foam body according to the invention or

Foam core composite or sandwich materials may be used in particular in the

Series production, e.g. for bodywork or interior trim in the automotive industry,

Interior parts in rail vehicle or shipbuilding, in the aerospace industry, in the

Mechanical engineering, in the production of sports equipment, in furniture construction or in the construction of wind turbines. Overall, rigid foam cores according to the invention are suitable in principle for any type of lightweight construction.

Claims

2Ü15ÜÜ2Ö5 WO 2017/067867 13 PCT / EP2016 / 074825 claims

1. A process for the production of complex foam cores, comprising the following process steps: a. Producing a particle filled, made of a film. Filler core, b. Insert the filler core into a tool and then close the tool, c. Filling pre-foamed or unfoamed matrix particles into the cavity between the filling core and the inner wall of the tool, d. Foaming the matrix particles, opening the tool and removing the hard foam core, e. optional opening of the film at the accessible former contact area from process step b. and f. Removal of the particles from the hard foam core.

2. The method according to claim 1, characterized in that the filling core in step b. is inserted so that the filling core between 0.5 and 10 area percent of

Touched inside wall of the tool.

3. The method according to claim 1, characterized in that the filling core in step b. is inserted such that the filling core after process step d. is completely surrounded by the foam, and that the foam in step e. partially drilled or cut open to the particles in step f. refer to.

4. The method according to claim 1, characterized in that the filling core in step b. is inserted so that the filling core between 0.5 and 10 area percent of

Touched inside wall of the tool, and that this point is closed with an easily removable device, and that this device in step e. Will get removed.

5. The method according to any one of claims 1 to 4, characterized in that it is at the particles to sand, at the Schäumungstemperatur stable and solid

Polymer particles, metal particles or glass beads is.

6. The method according to any one of claims 1 to 5, characterized in that it is the film to a PTFE, PEEK or PPSU film or a silicone-containing paper Ü15ÜÜ2Ö5

WO 2017/067867 14 PCT / EP2016 / 074825

or a silicone-containing film, and that this optionally after process step f. is pulled out of the hard foam core.

7. The method according to any one of claims 1 to 6, characterized in that in method step a. the filling core is tightly packed and shaped by means of a press and / or by applying negative pressure.

8. The method according to any one of claims 1 to 7, characterized in that the filling core is open at one point and the filling core is hung at this open position in the tool.

9. The method according to any one of claims 1 to 8, characterized in that the inside of the tool before step b. or c. with a material forming a subsequent cover layer, preferably with prepregs or organo sheets is designed.

10. The method according to any one of claims 1 to 9, characterized in that the outside of the filling core before step b. or c. with a material, forming a later topcoat, preferably with prepregs or organo sheets is occupied. 1 1. A method according to any one of claims 1 to 10, characterized in that the filling core in step b. is inserted so that it touches the inner wall of the tool at least two places, and that in step f. the particles are blown out of the cavity by means of compressed air.

12. The method according to any one of claims 1 to 1 1, characterized in that it concerns the matrix particles prefoamed P (M) I particles having a particle size between 1, 0 and 25.0 mm or P (M) l -Suspensionspolymerisate with a particle size between 0, 1 and 1, 0 mm is.

13. The method according to any one of claims 1 to 12, characterized in that the matrix particles in step f. preheated be filled under pressure, and that the foaming takes place at the foaming temperature by lowering the pressure.

14. The method according to any one of claims 1 to 13, characterized in that the matrix particles in step c. be sucked into the tool and / or blown.

15. The method according to any one of claims 1 to 14, characterized in that the cavity between the filling core and the inside of the tool in step c. to a

Fill level between 50 and 100% filled with matrix particles. Ü15ÜÜ2Ö5

WO 2017/067867 15 PCT / EP2016 / 074825

6. The method according to any one of claims 1 to 15, characterized in that the matrix particles prior to the addition in in step c. in a storage container at a temperature which is less than 50 ° C below the foaming temperature, and at a pressure which is at least 1 bar above the normal pressure, stored and batchwise in process step c. are filled in the tool, wherein after the batch-wise filling in each case the connection between the reservoir and the tool is closed.

7. Foam body or a foam core containing sandwich material, characterized

in that it has a cavity connected at least at one point to the surface of the foam core, and that there is a film, a cured prepreg or organic sheet or none at all between the foam core and the hollow space.