DE102011013516A1 - Method for manufacturing mold part e.g. A-column, in cladding part in body construction of automobile, involves processing mold part, where preferential direction of foaming lies perpendicular to propagation direction of foaming material - Google Patents

Abstract

The method involves filling a tool cavity with a foaming material and a reinforcement material such as reinforcing fiber e.g. glass fibers, carbon fiber, aramid fiber, boron fiber, metal fiber and calcium titanate fiber. The foaming material is foamed in a preferential direction, and a foamed mold part is removed, where the foaming material contains a matrix material selected from a group consisting of plastic, metal and ceramics. The mold part is processed, where a preferential direction of foaming lies perpendicular to a propagation direction of the foaming material in the tool cavity.

Description

The present invention relates to a process for the production of reinforced, in particular fiber-reinforced, foam molded parts as well as the molded parts produced by this process. In particular, the invention relates to a modified foam injection molding process. In the method according to the invention, the steps of molding and foaming are preferably carried out separately, the foaming taking place in particular in a preferred direction, in particular perpendicular to the preferred direction of filling the mold cavity.

Foamed plastics (plastic foams) are used in many areas of technology. Due to their advantageous properties, such as low density, low thermal and acoustic conductivity and largely inherent stress-free processability, they have great technical importance. You will find, for example, use as a technical molding, as heat and sound insulation material, eg. B. in the construction and vehicle sector, or as packaging and cushioning material.

Due to the low density of foams, the use of foams, inter alia, in the automotive industry, in particular in the body shop, of particular importance. However, the pore structure of the foams has a disadvantageous effect on the mechanical performance of the components, which is very pronounced in particular under tensile loading but also under pressure or shear stress.

Foams or foams are generally understood to mean a mixture in which gas-sensed cavities (bubbles) are finely distributed in a liquid or a solid (matrix material). For the production of foams, in principle, all plastics and various processes are suitable. Furthermore, ceramic or metallic foams and processes for their preparation are known.

Foams can be subdivided into open-cell (sponge-like), closed-cell and mixed-cellular foams based on their cell or pore structure. With open-cell foams, the existing surrounding medium (eg air) can circulate freely between the individual cells, which is not possible with closed-cell foams. If a foam contains both open and closed cells, this is called a mixed cell structure. So-called integral foams usually have a lightweight, cellular core and a compact, closed outer skin.

In the prior art, various methods for the production of foams are known, which can generally distinguish between the type of gas production between chemical, physical and mechanical blowing process. A foaming process generally involves the creation of materials having a foam structure, that is, the formation of a pore or cell structure in the material of interest.

• i) Bereitstellen eines flüssigen Ausgangsstoffs, z. B. eine Thermoplast-Schmelze,
• ii) Erzeugung von Gasblasen in der flüssigen Stoffphase durch mechanische, chemische oder physikalische Prozesse,
• iii) Verfestigung des gebildeten Schaumzustandes, z. B. durch Abkühlen.

In general, you can the following three stages in the production of foams, z. As plastic foams, distinguish:

• i) providing a liquid starting material, for. B. a thermoplastic melt,
• ii) production of gas bubbles in the liquid phase by mechanical, chemical or physical processes,
• iii) solidification of the foam state formed, z. B. by cooling.

As a rule, in fiber-reinforced materials, the high mechanical strengths and stiffnesses of the fiber material are made usable by embedding the fibers in a matrix and combined with the pressure stability of the matrix material (eg the polymer). Decisive for the mechanical stability here is in particular the adhesion between the fiber and the matrix material.

Various processes are known to the person skilled in the art for the production of fiber-reinforced foams. It is generally possible to disperse reinforcing fibers in the foam product or, for example, to foam a reinforcing fiber-added thermoplastic by a common foaming process.

Extrusion, thermoplastic foam injection molding (TSG), MuCell process and reaction foam casting process (RSG) or reaction foam injection molding process (RIM (Reaction Injection Molding method).

The thermoplastic foam injection molding (TSG) operates in principle like a conventional injection molding process, wherein the thermoplastic material, a blowing agent, for example a chemical blowing agent such as azodicarboxylic acid diamide is added. Upon exiting the injection molding nozzle, foaming of the foamable material takes place at the same time. In order for the dynamic pressure to be above the gas pressure of the propellant, and thus premature foaming of the melt in the cylinder is prevented, a closure nozzle must be used.

Also known is the so-called MuCell method, which as a modified foam injection molding process can be considered. In the MuCell process, a gas compressed to a supercritical fluid is used as the physical propellant which is injected into the thermoplastic melt.

Also known is the so-called dolphin process. This is a combined process for the production of molded parts consisting of a structural part and a foam pad. Here, in a first step, the molding z. B. made by injection molding of an optionally fiber-reinforced thermoplastic. In a second step, the structural part is rotated in a second cavity, in which then a foamable material is sprayed. It may be z. Example, to act with a propellant gas (eg., Nitrogen) loaded thermoplastic. After a delay time, the foaming of the material takes place by means of a precision opening stroke of the second cavity.

Various processes for the production of reactive foams and fiber-reinforced reactive foams are known to the person skilled in the art. The process sequence of a reaction foam casting process or reaction foam injection process (eg RIM (Reaction Injection Molding) process) consists essentially in metering and mixing the reaction components, introducing the reaction mixture into the mold cavity, reaction of the components, foaming (possibly in a separate step) and the removal of the molding from the mold cavity.

A problem in the production of fiber-reinforced foams is generally that the fibers, in particular long fibers with a length of more than 2 mm, such as glass fibers, for one not individually dispersed in the foam and on the other hand have no preferred orientation in the foam. This has the consequence that the introduction of reinforcing fibers into foams often causes only a very little or no mechanical reinforcing effect.

In the prior art, various technically complex methods are described which are intended to ensure alignment of the reinforcing fibers in the foam.

In US 3,867,494 describes a process for producing a glass fiber reinforced polyurethane in which a glass fiber layer is impregnated with a foamable liquid.

In the Canadian patent application CA 1090521 Also, a process for making fiber reinforced plastics is described by first aligning a fiber layer which is then treated in a special manner with a foamable resin.

The methods described above are technically very complicated to carry out and limited to special fiber / foam systems. It is therefore an object of the present application to provide a simple, cost-effective and versatile method for the production of fiber-reinforced foams, which have a preferred fiber direction, and thus an improved mechanical stability.

Another object of the invention is to provide a method for producing a molded part, comprising a structural part, in particular a plastic structural part, and a foam pad, wherein in addition to a good mechanical stability good compatibility and adhesion of structural part and foam pad are given.

It has surprisingly been found that fiber-reinforced foams having individually distributed and oriented in a preferred direction fibers can be produced in a simple and applicable to almost all foams process. The shaping step and the foaming step are preferably separated from each other and can be carried out in a special way, which may in particular lead to an orientation or reorientation of the fiber. The process according to the invention can be used in particular for the production of plastic foams, preferably based on thermoplastic polymers or reactive foams (such as, for example, polyurethane).

Methods are already known in the art for a thermoplastic foam injection molding process wherein the step of tooling (injection molding step) is separate from the foaming step. The document WO 98/16364 describes a method for injection molding of foams, in which the foaming of the thermoplastic material takes place by means of a piston which is movable parallel to the direction of injection in the injection molding apparatus.

• a) Befüllen einer Werkzeugkavität (K) mit mindestens einem schaumfähigen Material (S) und mindestens einem Verstärkungsmaterial (VM),
• b) Aufschäumen des schaumfähigen Materials (S),
• c) Entnahme des aufgeschäumten Formteils,
• d) gegebenenfalls weitere Bearbeitung des Formteils, wobei das Aufschäumen in Schritt b) in einer Vorzugsrichtung erfolgt, und wobei die Vorzugsrichtung des Aufschäumens im Wesentlichen senkrecht zur Ausbreitungsrichtung des schaumfähigen Materials (S) in der Werkzeugkavität (K) (im Schritt a) liegt.

The present invention is directed to a method for producing a molded part, in particular a fiber-reinforced molded part, in particular a fiber-reinforced plastic molded part, comprising the following steps:

• a) filling a tool cavity (K) with at least one foamable material (S) and at least one reinforcing material (VM),
• b) foaming the foamable material (S),
• c) removal of the foamed molding,
• d) optionally further processing of the molded part, wherein the foaming in step b) takes place in a preferred direction, and wherein the preferred direction of the foaming is substantially perpendicular to the direction of propagation of the foamable material (S) in the Werkzeugkavität (K) (in step a).

The present invention is in particular directed to a process for the preparation of a molded article containing the (or consisting of) the above-mentioned steps (s):
wherein the spreading of the foamable material (S) takes place during filling of the tool cavity (K) in step a in a preferred direction (propagation direction),
wherein the foaming in step b) takes place in a preferred direction,
and wherein the preferred direction of foaming is substantially perpendicular to the direction of propagation of the foamable material (S) in the mold cavity (K) during filling of the mold cavity in step a).

In particular, the foamable material (S) contains at least one matrix material (M), preferably selected from the group consisting of plastics, metals and ceramics, and at least one blowing agent (T). The propellant (T) may be selected from known chemical, physical or mechanical propellants. Here, a combination of different blowing agents described below is conceivable.

The matrix material (M) described below is preferably the main component of the foamable material (S). The foamable material (S) usually contains the main component in an amount of more than 50% by weight, preferably more than 70% by weight. -%, in particular more than 90 wt .-% (in each case based on the total weight of foamable material).

The foamable material (S) comprises preferably from 70% by weight to 99.9% by weight, in particular from 90% by weight to 99% by weight, particularly preferably from 95% by weight to 99% by weight, of Matrix material, preferably a thermoplastic material; and 30 wt .-% to 0.1 wt .-%, in particular 10 wt .-% to 1 wt .-%, particularly preferably 5 wt .-% to 1 wt .-%, of blowing agent (T). Frequently, a chemical blowing agent is used. The percentages by weight are based on the total weight of the foamable material.

The foamable material (S) may optionally contain other additives. These are, for example, customary flame retardants and further additives known to the person skilled in the art, which are usually added to plastics.

A preferred embodiment of the invention relates to the above-described method for producing a molded part, wherein the matrix material (M) of the foamable material (S) is a thermoplastic material.

• a) Polyester, wie zum Beispiel Polyethylenterephthalat (PET) oder Polybutylenterephthalat (PBT);
• b) Polyamide, wie zum Beispiel Polyamide 6, Polyamide 11, Polyamide 6/6, Polyamide 6/10, Polyamide 6/12, Polyamide 11 oder Polyamide 12;
• c) Polyether, wie zum Beispiel Polyethylenglykol (PEG), Polypropylenglykol oder Polyethersulfone (PESU oder PES);
• d) Polyacrylate, wie zum Beispiel Polymethacrylsäureester, Polymethacrylat oder Polyacrylnitril;
• e) Polyolefine, wie zum Beispiel Polyethylen (HTPE(high-temperature-polyethylene), LTPE (low-temperature-polyethylene)), Polypropylen oder Polybuten-1, Polytetrafluoroethylen;
• f) Polyacetale, wie zum Beispiel Polyoxyethylen (POM);
• g) Polymere aus Vinylgruppen enthalten Monomeren, wie zum Beispiel Polyvinylchlorid, Polyvinylidenchloride, Polystyrol, schlagzäh-modifiziertes Polystyrol, Polyvinylcarbazol, Polyvinylacetat oder Polyvinylalkohol;
• h) Styrol-Copolymerisate, wie zum Beispiel Styrol-Acrylnitril-Copolymere (SAN), Acrylnitril-Butadien-Styrol-Copolymere (ABS) oder Styrol-Butadien-Copolymere (SB).

In particular, the foamable material (S) contains as main component at least one thermoplastic as matrix material and as further component a chemical, physical or chemical blowing agent (T). The matrix material (M) contains or is in particular at least one thermoplastic plastic selected from the following group:

• a) polyesters, such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT);
• b) polyamides such as polyamides 6, polyamides 11, polyamides 6/6, polyamides 6/10, polyamides 6/12, polyamides 11 or polyamides 12;
• c) polyethers such as polyethylene glycol (PEG), polypropylene glycol or polyethersulfones (PESU or PES);
• d) polyacrylates, such as polymethacrylic acid ester, polymethacrylate or polyacrylonitrile;
• e) polyolefins, such as high-temperature polyethylene (HTPE), low-temperature polyethylene (LTPE), polypropylene or polybutene-1, polytetrafluoroethylene;
• f) polyacetals such as polyoxyethylene (POM);
• g) polymers of vinyl groups include monomers such as polyvinyl chloride, polyvinylidene chlorides, polystyrene, toughened polystyrene, polyvinylcarbazole, polyvinyl acetate or polyvinyl alcohol;
• h) styrene copolymers, such as, for example, styrene-acrylonitrile copolymers (SAN), acrylonitrile-butadiene-styrene copolymers (ABS) or styrene-butadiene copolymers (SB).

Preferably contains (or consists of) the foamable material (S) is a thermoplastic material (matrix material (M)), and a blowing agent (T), wherein the thermoplastic material is in particular selected from the group consisting of polyesters, polyamides, polyolefins, polystyrene, Styrene-acrylonitrile copolymers (SAN) and acrylonitrile-butadiene-styrene copolymers (ABS).

Furthermore, an embodiment of the invention is preferred, wherein a thermoplastic plastic selected from the group consisting of polyethylene, polypropylene, polybutene-1, polytetrafluoroethylene, polyamide 6, polyamide 11, polyamide 6/6, polyamide 6/10 or polyamide 6/12, polyethylene terephthalate , Polybutylene terephthalate, Polycarbonate, poly (meth) acrylic esters, polymethacrylate, polyacrylonitrile, polyoxymethylene, polyvinylchloride, polyvinylidene chloride, polyvinylcarbazole, polyvinylacetate, polyvinylalcohol, polystyrene, impact-modified polystyrene, acrylonitrile-butadiene-styrene copolymers, styrene-acrylonitrile copolymers, acrylic ester-styrene-acrylonitrile copolymers, polyethersulfone and polyetherimide is used.

Preferably, the foamable material (S) comprises a thermoplastic material (matrix material (M)), and a blowing agent (T), wherein the thermoplastic material is a polyamide.

Furthermore, it is also possible to use mixtures of the abovementioned polymers or copolymers of the monomer units used to form the abovementioned polymers.

• a) Polyurethanen (PU), wobei das Reaktionsgemisch in der Regel eine Isocyanat-Komponente (z. B. ein Polyisocyanat-Präpolymer) und eine Polyol-Komponente (z. B. kurzkettige Di- oder Polyole, wie Glykole, Glycerin, Butandiol, Trimethylolpropan, Polyetherpolyole, Poyesterpolyole) und/oder ein Prä-Kondensat aus den genannten Komponenten enthält;
• b) Polyepoxiden (Epoxidharze, EP), wobei das Reaktionsgemisch in der Regel eine Epoxid-Komponente (z. B. Epichlorhydrin) und eine Di-/Polyol-Komponenten (z. B. Bisphenol A) und/oder ein Epoxid-Präpolymer aus den genannten Komponenten und/oder eine Mischung eines Epoxid-Präpolymer und einem Härter (z. B. einer Polyamin-Komponente, wie Trieethyltetraamine TETA) enthält;
• c) Phenolharzen (Phenoplaste, PF), wobei das Reaktionsgemisch in der Regel eine Phenol-Komponente und Formaldehyd und/oder ein Prä-Kondensat aus den genannten Komponenten enthält;
• d) Harnstoff-Formaldehyd-Harzen (UF-Harze), wobei das Reaktionsgemisch in der Regel eine Harnstoff-Komponente und eine Aldehyd-Komponente (z. B. Formaldehyd) und/oder ein Prä-Kondensat aus den genannten Komponenten enthält;
• e) gesättigte und ungesättigte Polyesterharzen, wobei das Reaktionsgemisch in der Regel eine Di- oder Polyol-Komponente (z. B. Glykole, Glyzerin) und eine gesättigte oder ungesättigte Dicarbonsäure-Komponente und/oder ein Prä-Kondensat aus den genannten Komponenten enthält.

In a further embodiment of the invention, the foamable material (S) contains as matrix material (M) in particular a reaction mixture which contains starting materials for the production of a thermoplastic or thermosetting plastic, as well as a blowing agent (T). The thermoplastic or thermosetting plastic produced starting from the respective reaction mixture can in particular be selected from:

• a) polyurethanes (PU), the reaction mixture generally comprising an isocyanate component (eg a polyisocyanate prepolymer) and a polyol component (eg short-chain di- or polyols, such as glycols, glycerol, butanediol, Trimethylolpropane, polyether polyols, polyester polyols) and / or a pre-condensate of said components;
• b) Polyepoxides (epoxy resins, EP), wherein the reaction mixture usually comprises an epoxide component (eg epichlorohydrin) and a di- / polyol component (eg bisphenol A) and / or an epoxide prepolymer the said components and / or a mixture of an epoxy prepolymer and a curing agent (eg a polyamine component, such as triethyltetraamine TETA);
• c) phenolic resins (phenolic, PF), wherein the reaction mixture usually contains a phenol component and formaldehyde and / or a pre-condensate of said components;
• d) urea-formaldehyde resins (UF resins), the reaction mixture generally containing a urea component and an aldehyde component (eg formaldehyde) and / or a pre-condensate of the named components;
• e) saturated and unsaturated polyester resins, wherein the reaction mixture usually contains a di- or polyol component (eg, glycols, glycerine) and a saturated or unsaturated dicarboxylic acid component and / or a pre-condensate of said components.

Preferably, the foamable material (S) contains a reaction mixture which contains starting materials for the production of a plastic, and a blowing agent (T), wherein the plastic produced from the reaction mixture can be selected in particular from the group consisting of polyurethanes, epoxy resins, phenolic resins and urea Formaldehyde resins, particularly preferably selected from polyurethanes and epoxy resins.

In a preferred embodiment of the invention, the foamable material (S) comprises at least one matrix material (M) consisting of at least one plastic and at least one blowing agent (T), wherein the plastic is selected from the group consisting of polyurethanes, epoxy resins, phenolic resins, urea Formaldehyde resins, polyesters, polyamides, polyolefins, polystyrenes, styrene-acrylonitrile copolymers (SAN) and acrylonitrile-butadiene-styrene copolymers (ABS), particularly preferably selected from polyurethanes, epoxy resins and polyamides.

In a further embodiment of the invention, the foamable material (S) consists of the above-described matrix material (main component) and the blowing agent (T).

However, the foamable material (S) used can also contain other additives. These are, for example, customary fillers, plasticizers, impact modifiers, flame retardants and other additives known to the person skilled in the art, which additives are usually added to polymers, in particular foams.

In the process according to the invention, preference is given to using at least one blowing agent (T) selected from the known chemical, physical or mechanical blowing agents known to the person skilled in the art.

• a) chemische Treibmittel
• b) physikalische Treibmittel, wie zum Beispiel niedere Alkane (z. B. Pentan),
• c) mechanische Treibmittel, wie zum Beispiel Stickstoff, Luft, Kohlendioxid.

For example, the following blowing agents can be used:

• a) chemical blowing agents
• b) physical blowing agents, such as lower alkanes (eg pentane),
• c) mechanical blowing agents, such as nitrogen, air, carbon dioxide.

In particular, substances or mixtures of substances can be used as the chemical blowing agent which split off at elevated temperatures, in particular at temperatures in the range of 130 ° C to 250 ° C, gas, preferably nitrogen or carbon dioxide. Such chemical blowing agents are known in the art and described in the literature. Preferred chemical blowing agents are 1,1'-azobis (formamide), sulfohydrazides such as 4,4'-oxibisbenzenesulfohydrazide, p-toluenesulfonylhydrazide or p-toluenesulfonyl semicarbazide, dinitrosopentamethylenetetramine, phenyltetrazole, alkali metal carbonates or bicarbonates, mixtures of alkali metal carbonate or bicarbonate and inorganic or organic acids. It is also possible to use mixtures of two or more of the compounds mentioned as blowing agent (T).

In particular, sodium carbonate or sodium bicarbonate can be used. As a very particularly preferred chemical blowing agent, a mixture of sodium bicarbonate and citric acid is used; this mixture preferably consists of 10% by weight to 90% by weight, in particular 20% by weight to 80% by weight, particularly preferably 30% by weight to 70% by weight, of sodium hydrogencarbonate and 90% by weight. % to 10 wt .-%, in particular 80 wt .-% to 20 wt .-%, particularly preferably 70 wt .-% to 30 wt .-%, of citric acid, wherein the wt .-% are each based on the total weight of Sodium bicarbonate and citric acid and together give 100 wt .-%.

In a preferred embodiment of the invention, the foamable material (S) is foamed in step b) of the process described by means of a physical and / or chemical blowing agent (T).

In a further preferred embodiment of the invention, the foaming of the foamable material (S) in step b) of the process according to the invention is carried out by applying reduced pressure and / or increasing the temperature. The application of negative pressure refers to the pressure in the mold cavity. The applied negative pressure can be in the range from 0.01 to 1 bar, preferably in the range from 0.1 to 1 bar, more preferably in the range from 0.5 to 1 bar. The temperature used depends on the matrix material-blowing agent system and can in particular in the range of 50 ° C to 300 ° C, preferably in the range of 80 ° C to 250 ° C, more preferably in the range of 130 ° C to 250 ° C. lie.

In the case of a physical foaming with a physical blowing agent, the gas evolution is generally carried out by outgassing of the blowing agent, for example a volatile organic solvent as a result of a reduction in pressure and / or temperature increase. In the case of a chemical foaming with a chemical blowing agent, the gas is evolved by the decomposition of the blowing agent to form a gaseous product, in particular as a result of a temperature increase or by a gas which is formed in the polymerization reaction, for. B. carbon dioxide in the polycondensation of polyurethanes. In the case of mechanical foaming, the gaseous blowing agent is introduced into the foamable material by means of a mechanical mixing process (eg MuCell process).

Known reinforcing fibers (VF) or known reinforcing nanoscale fillers (also referred to below as nanomaterials) may be used as reinforcing material (VM). Nanomaterials contain particles that typically range from 1 to 500 nm.

In one embodiment of the invention, combinations of reinforcing fibers (VF) and nanoscale fillers can also be used as reinforcing material (VM). A preferred embodiment relates to the use of at least one reinforcing fiber.

A further embodiment of the invention relates to a method described above, characterized in that the reinforcing material (VM) is a nanoscale filler.

• a) Befüllen einer Werkzeugkavität (K) mit mindestens einem schaumfähigen Material (S) und mindestens einer Verstärkungsfaser (VF),
• b) Aufschäumen des schaumfähigen Materials (S),
• c) Entnahme des aufgeschäumten Formteils,
• d) gegebenenfalls weitere Bearbeitung des Formteils,

wobei das Aufschäumen (Schritt b) in einer Vorzugsrichtung erfolgt, und wobei die Vorzugsrichtung des Aufschäumens im Wesentlichen senkrecht zur Ausbreitungsrichtung des schaumfähigen Materials (S) in der Werkzeugkavität (K) (Schritt a) liegt.A preferred embodiment of the invention relates to a method for the production of a molded part comprising the following steps:

• a) filling a tool cavity (K) with at least one foamable material (S) and at least one reinforcing fiber (VF),
• b) foaming the foamable material (S),
• c) removal of the foamed molding,
• d) optionally further processing of the molded part,

wherein the foaming (step b) takes place in a preferred direction, and wherein the preferred direction of foaming is substantially perpendicular to the propagation direction of the foamable material (S) in the mold cavity (K) (step a).

For the purposes of the present invention, the preferred direction can be understood to mean that the spreading or foaming takes place essentially in this direction, for example at least 60 percent (in particular at least 80 percent) of the material being spread or foamed in this direction.

• a) anorganischen Verstärkungsfasern, wie Borfasern, Glasfasern, Kohlenstofffasern, Kieselsäurefasern, Keramikfasern und Basaltfasern;
• b) organischen Verstärkungsfasern, wie Aramidfasern, Polyesterfasern, Nylonfasern, Polyethylenfasern und Plexiglasfasern;
• c) und Naturfasern, wie Holzfasern, Flachsfasern, Hanffasern und Sisalfasern.

As a reinforcing fiber (VF) can in principle any, known in the art, in particular for the reinforcement of foams usual, Fiber can be used. In particular, one or more reinforcing fibers selected from known ones may be used:

• a) inorganic reinforcing fibers such as boron fibers, glass fibers, carbon fibers, silica fibers, ceramic fibers and basalt fibers;
• b) organic reinforcing fibers such as aramid fibers, polyester fibers, nylon fibers, polyethylene fibers and Plexiglas fibers;
• c) and natural fibers such as wood fibers, flax fibers, hemp fibers and sisal fibers.

In particular, glass fibers, carbon fibers, aramid fibers, boron fibers, metal fibers or potassium titanate fibers are particularly suitable for use in the described method and molding. Particular preference is given to using glass fibers.

The fibers mentioned can be used in the form of short fibers, long fibers or as a mixture of short and long fibers. In this case, the short fibers preferably have an average fiber length in the range of 0.1 to 1 mm. Further preferred are fibers having an average fiber length in the range of 0.5 to 1 mm.

The long fibers used preferably have an average fiber length in the range of 1 to 50 mm, furthermore preferred are fibers having a mean fiber length in the range of more than 1 mm.

In a preferred embodiment of the invention, glass fibers having an average fiber length in the range of 0.5 to 5 mm, particularly preferably in the range of 0.5 to 2 mm are used.

Another embodiment of the invention relates to the described method for producing a molded part, wherein the reinforcing material (VM) is a nanoscale filler.

In particular, reinforcing nanoscale fillers may be used as reinforcing material (VM), one or more fillers selected from the group consisting of carbon nanotubes, carbon black, nanoscale sheet silicates, nanoscale aluminum oxide (Al ₂ O ₃ ), nanoscale titanium dioxide (TiO ₂ ) and nanoscale Silica (SiO ₂ ).

• a) Befüllen einer Werkzeugkavität (K) mit mindestens einem schaumfähigen Material (S) und mindestens einer Verstärkungsfaser (VM),
• b) Aufschäumen des schaumfähigen Materials (S),
• c) Entnahme des aufgeschäumten Formteils aus der Werkzeugkavität (K),
• d) gegebenenfalls weitere Bearbeitung des Formteils,

wobei das Aufschäumen in Schritt b) in einer Vorzugsrichtung erfolgt, und wobei die Vorzugsrichtung des Aufschäumens im Wesentlichen senkrecht zur Ausbreitungsrichtung des schaumfähigen Materials (S) beim Befüllen der Werkzeugkavität (K) (Schritt a) liegt.The present invention relates to a method for producing a molded part, in particular a fiber-reinforced molded part from a foam plastic, comprising (essentially) the following steps:

• a) filling a tool cavity (K) with at least one foamable material (S) and at least one reinforcing fiber (VM),
• b) foaming the foamable material (S),
• c) removal of the foamed molding from the mold cavity (K),
• d) optionally further processing of the molded part,

wherein the foaming in step b) takes place in a preferred direction, and wherein the preferred direction of the foaming is substantially perpendicular to the propagation direction of the foamable material (S) during filling of the mold cavity (K) (step a).

The process step a described above (filling the mold cavity) can be carried out in particular by means of a master mold process known to the person skilled in the art for the production of molded parts, in particular plastic molded parts. The method step a (filling of the tool cavity) described above is preferably selected by means of a method selected from the group consisting of thermoplastic foam casting method (TSG), thermoplastic foam injection molding method, foam pressing method, foam injection stamping method, RTM method (Resin Transfer Molding), MuCell Process and reaction injection molding (RSG, RIM (Reaction Injection Molding) method) performed. Preferred is a method described above, wherein the filling of the mold cavity (K) in step a) takes place in an injection molding process.

Optionally, even in method step a), partial foaming of the foamable material (S) may occur.

The reinforcing material, in particular the reinforcing fiber, may for example be mixed with the foamable material (S) or with the matrix material of the foamable material (M) (such as, for example, a thermoplastic melt) prior to filling the cavity. The loading with the propellant (T) can take place, for example, after mixing with the reinforcing material (VM).

However, it is also conceivable first to mix the matrix material (M) with the blowing agent (T) and only then to mix in the reinforcing material (VM).

A further embodiment of the invention consists of separately filling the foamable material (S) and the reinforcing material (VM), in particular the reinforcing fiber (VF), into the cavity.

The foamable material (S) consisting of matrix material (M) and blowing agent (T) can in principle be prepared by all methods known to those skilled in the art and used in process step a).

Foams or foams in the context of the present invention are understood to mean a mixture in which gas-sensed cavities (bubbles) are finely distributed in a liquid or a solid (matrix material). For the production of foams, in principle, all plastics and various processes are suitable.

For the purposes of the present invention, a foaming or foaming process involves the creation of materials having a foam structure, that is, the formation of a pore or cell structure in the material in question.

The propagation direction in the sense of the present invention means the preferred direction in which a filling of the tool cavity by the foamable material (S) takes place in step a of the method according to the invention. This direction of propagation depends on the type and geometry of the filling device and the mold cavity. The preferred direction of propagation of the foamable material (S) in the tool cavity or propagation direction is perpendicular to the propagation plane or propagation surface (eg, the flow front of the thermoplastic melt) of the foamable material in the tool cavity.

The propagation plane preferably lies in the parting plane of the tool cavity (K).

Optionally, the propagation direction, i. H. the preferred direction of propagation of the foamable material (S) in the cavity may be affected or enforced by appropriate means, such as by continuously opening the mold cavity during filling of the mold cavity in step a).

In a preferred embodiment, the filling device and the geometry of the tool cavity are designed such that the propagation direction (substantially) corresponds to the filling direction. Thus, the foaming can take place, for example, by opening the mold cavity, wherein the opening direction takes place, for example, (substantially) perpendicular to the injection direction of the nozzle in a thermoplastic injection molding process.

Substantially perpendicular to the direction of propagation of the foamable material in the mold cavity means that the preferred direction of the foaming, which can be achieved for example by opening the mold cavity, with the propagation direction of the foamable material an angle in the range of 70 ° to 110 °, preferably in the range from 80 ° to 100 °, more preferably in the range of 85 ° to 95 °.

In particular, when filling the tool cavity in step a) of the method according to the invention, there is a certain orientation of the fiber in the propagation direction of the foamable material in the tool cavity. In particular, in the second process step b), a reorientation of the fiber in the preferred direction of the foaming takes place. In this sense, a preferred embodiment of the invention relates to a method as described above, wherein the preferred direction of foaming in step b) substantially perpendicular to the direction of the preferred fiber orientation, which results after the filling step a) takes place.

In the direction of the preferred fiber orientation in the sense of the invention, the direction in which at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90% of the reinforcing fibers have aligned, is to be understood.

In particular, an embodiment of the invention relates to a method as described above, wherein the foamable material (S) during filling tool cavity (K) in step a) in a preferred direction or plane in the mold cavity propagates, and wherein the foaming in Step b) takes place substantially perpendicular to the preferred direction of propagation of the foamable material (S) in the mold cavity. Foaming of the foamable material (S) in step b) preferably takes place with orientation and / or reorientation of the reinforcing fiber (F) in the preferred direction of foaming.

Furthermore, the present invention relates to a method as described above, wherein the foaming of the foamable material (S) in step b) by opening the Werkzeugkavität (K), and wherein the opening of the Werkzeugkavität (K) substantially perpendicular to the propagation direction of the foamable material (S) in the mold cavity (K) (step a) takes place.

A preferred embodiment of the invention relates to a method described above, wherein the filling of the Werkzeugkavität (K) in step a) takes place in an injection molding, wherein preferably the reinforcing fibers (VF) during filling of the Werkzeugkavität (K) in a preferred direction - in particular Direction of propagation - to be aligned; and wherein the foaming in step b) by opening the Werkzeugkavität (K) in the Preferred direction of the foaming takes place, wherein the preferred direction of foaming is substantially perpendicular to the preferred direction of the fiber orientation after step a).

• a) Befüllen einer Werkzeugkavität (K) mit mindestens einem schaumfähigen Material (S) und mindestens einem Verstärkungsmaterial (VM),
• b) Aufschäumen des schaumfähigen Materials (S),
• c) Entnahme des aufgeschäumten Formteils,
• d) gegebenenfalls weitere Bearbeitung des Formteils,

wobei das Aufschäumen in Schritt b) in einer Vorzugsrichtung erfolgt, und wobei die Vorzugsrichtung des Aufschäumens im Wesentlichen senkrecht zur Ausbreitungsrichtung des schaumfähigen Materials (S) in der Werkzeugkavität (Schritt a) liegt;
wobei das schaumfähige Material (S) einen Kunststoff, bevorzugt einen thermoplastischen Kunststoff, besonders bevorzugt ein Polyamid, und ein Treibmittel (T) enthält (bevorzugt daraus besteht);
wobei das Befüllen der Werkzeugkavität (K) in Schritt a) in einem Spritzgießverfahren erfolgt;
und wobei das Aufschäumen in Schritt b) durch Öffnen der Werkzeugkavität (K) in der Vorzugsrichtung des Aufschäumens erfolgt.A preferred embodiment of the invention relates to a method described above comprising the following steps:

• a) filling a tool cavity (K) with at least one foamable material (S) and at least one reinforcing material (VM),
• b) foaming the foamable material (S),
• c) removal of the foamed molding,
• d) optionally further processing of the molded part,

wherein the foaming in step b) takes place in a preferred direction, and wherein the preferred direction of the foaming is substantially perpendicular to the propagation direction of the foamable material (S) in the mold cavity (step a);
wherein the foamable material (S) comprises (preferably consists of) a plastic, preferably a thermoplastic, more preferably a polyamide, and a blowing agent (T);
wherein the filling of the mold cavity (K) in step a) takes place in an injection molding process;
and wherein the foaming in step b) takes place by opening the mold cavity (K) in the preferred direction of foaming.

The foaming in a preferred direction (step b) can also be done by opening the cavity and then raising the temperature.

Another possibility to perform the foaming in a preferred direction according to step b) of the method according to the invention, then the non-foamed or only partially foamed molding, which in step a) made wound, in a second cavity to transfer and by reducing the pressure and / or Temperature increase foaming in a preferred direction, which is determined by the geometry of the cavity to perform.

In a particular embodiment, the invention relates to a method as described above, characterized in that at least a part of the foaming of the foamable material (S) in step b) is carried out under the influence of an electric and / or electromagnetic field. This may serve in particular to aid fiber orientation during foaming. This is particularly suitable, for example, for processes in which at least one polymer having charged groups is used as the matrix material of the foamable material (S) or else for processes for the production of metal or ceramic foam. Likewise, method step a) or both method steps a) and b) can be carried out entirely or partially under the influence of an electric and / or electromagnetic field.

Another embodiment of the invention relates to the combination of the method described above with the production of a structural part (ST). Thus, for example, first a structural part (ST) can be produced in a conventional injection molding process, in which case a reinforced, in particular fiber-reinforced, foam can be applied to this structural part (ST) according to the inventive method described above.

The structural part (ST) can in particular be produced from a thermoplastic and optionally from a reinforcing fiber. As thermoplastic material and as reinforcing material or reinforcing fiber, the materials described above in connection with the constituents of the foamable material (S) can preferably be used. Preferably, the structural part is made of a thermoplastic material selected from the group consisting of polyamides, polyolefins, polyesters and polystyrene, more preferably made of polyamide.

In particular, it is advantageous to combine two mutually compatible, for example chemically similar, thermoplastics. A preferred embodiment of the invention relates to the use of a polyamide structural part (ST) and a fiber-reinforced polyamide foam, which can be foamed by means of a physical or mechanical blowing agent.

• a1) Herstellen eines Strukturteils (ST) mittels eines Spritzgießverfahrens,
• a2) Befüllen einer Werkzeugkavität (K), welche in räumlicher Verbindung steht mit dem unter a1 hergestellten Strukturteil (ST), mit mindestens einem schaumfähigen Material (S) und mindestens einem Verstärkungsmaterial (VM), insbesondere mindestens einer Verstärkungsfaser,
• b) Aufschäumen des schaumfähigen Materials (S),
• c) Entnahme des aufgeschäumten Formteils,
• d) gegebenenfalls weitere Bearbeitung des Formteils,

wobei das Aufschäumen in Schritt b) in einer Vorzugsrichtung erfolgt, und wobei die Vorzugsrichtung des Aufschäumens im Wesentlichen senkrecht zur Ausbreitungsrichtung des schaumfähigen Materials (S) in der Werkzeugkavität (Schritt a2) liegt.Accordingly, a preferred embodiment of the invention relates to a method described above comprising the following steps:

• a1) producing a structural part (ST) by means of an injection molding process,
• a2) filling a tool cavity (K) which is in spatial connection with the structural part (ST) produced under a1, with at least one foamable material (S) and at least one reinforcing material (VM), in particular at least one reinforcing fiber,
• b) foaming the foamable material (S),
• c) removal of the foamed molding,
• d) optionally further processing of the molded part,

wherein the foaming in step b) takes place in a preferred direction, and wherein the preferred direction the foaming is substantially perpendicular to the direction of propagation of the foamable material (S) in the mold cavity (step a2).

The removal of the foamed molding takes place after foaming and possibly after cooling of the foamed molding. Depending on the configuration of the foaming step b), removal from the opened mold cavity (K) or removal from the additional cavity in which the foaming step was carried out can take place here.

The further processing of the molding may in particular include a surface treatment (eg, grinding, polishing), the removal of protruding edges, and / or the surface treatment with a functionalization composition (such as a flame retardant composition).

Moreover, the present invention also relates to moldings obtainable (or obtained) by a method as described above. In particular, the invention is directed to moldings containing (or consisting of) fiber-reinforced or reinforced with nanoscale fillers plastic foam. It is preferably a molding containing a thermoplastic material as the matrix material (M).

The molded parts can be characterized in that they contain a fiber-reinforced foam, wherein the fibers are substantially separated in the matrix material and substantially in the thickness direction of the molded part, d. H. in the preferred direction of the foaming, are aligned.

The present invention further relates to the use of the molded parts according to the invention, preferably the fiber-reinforced plastic foam moldings, in trim parts, in particular in the automotive sector, in particular in the bodywork construction for vehicles, in particular for the production of supporting vehicle pillars in the body construction, such as the production of A-pillar, B-pillar, C-pillar or D-pillar. But it is also the production of moldings for the interior of the automobile conceivable, such. For example, for ad consoles.

In addition, the moldings according to the invention may be suitable for all applications in which foam moldings with structural rigidity are required. The moldings according to the invention can find particular application in the construction of ships, aircraft or trains, in particular as trim parts, underbody components, instrument panels, shell structures for seats and bulkhead walls.

Furthermore, non-automotive applications of the moldings of the invention are conceivable, such as shuttering panels, trim elements, trays and housing components.

In particular, the method according to the invention described can serve to connect plastic structural part (eg B-pillar) in the body construction by foaming with the car body. Advantageously, in this case, the additional stability of the connecting foam part by introducing and aligning the reinforcing fiber effect.

Below is a brief description of the figures:

1 shows the schematic sequence of a method according to the invention.

In 1A the first method step is described, for. B. filling a cavity z. By injection molding of a fiber-reinforced polymer with dissolved propellant (chemically or physically), with the reinforcing fibers (shown as dashes) aligning in a preferred direction.

In 1B the opening of the filled tool in the direction of the arrow and the foaming (blistering) in the z-direction (substantially perpendicular to the propagation direction and the previous fiber orientation) is shown. This results in a substantial reorientation of the fibers (shown as lines) in the core layer due to the foaming motion or blistering.

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

• US 3867494 [0017]
• CA 1090521 [0018]
• WO 98/16364 [0022]

Claims (15)

Process for producing a molded part comprising the following steps: a) filling a tool cavity (K) with at least one foamable material (S) and at least one reinforcing material (VM), b) foaming the foamable material (S), c) removal of the foamed molding, d) optionally further processing of the foamed molding, wherein the foaming in step b) takes place in a preferred direction, and wherein the preferred direction of foaming is substantially perpendicular to the propagation direction of the foamable material (S) in the mold cavity (K) (step a). A method according to claim 1, characterized in that the foamable material (S) at least one matrix material (M) selected from the group consisting of plastics, metals and ceramics, and at least one blowing agent (T). Method according to one of claims 1 or 2, characterized in that the reinforcing material (VM) is a reinforcing fiber (VF). Method according to one of claims 1 to 3, characterized in that it is in the matrix material (M) of the foamable material (S) is a thermoplastic material. Method according to one of claims 1 to 4, characterized in that the matrix material (M) of the foamable material (S) is a thermoplastic material, and in that the reinforcing material is a reinforcing fiber (VF) selected from glass fibers, Carbon fibers, aramid fibers, boron fibers, metal fibers and potassium titanate fibers. Method according to one of claims 1 to 5, characterized in that the foamable material (S) is a matrix material (M) consisting of at least one plastic selected from the group consisting of polyurethanes, epoxy resins, phenolic resins, urea-formaldehyde resins, polyesters, polyamides, Polyolefins, polystyrenes, styrene-acrylonitrile copolymers (SAN) and acrylonitrile-butadiene-styrene copolymers (ABS), and optionally at least one blowing agent (T). Method according to one of claims 1 to 6, characterized in that the foaming of the foamable material (S) in step b) is carried out under application of negative pressure and / or temperature increase. Method according to one of claims 1 to 7, characterized in that the foaming of the foamable material (S) in step b) by opening the Werkzeugkavität (K), and wherein the opening of the Werkzeugkavität (K) substantially perpendicular to the propagation direction of the foamable Material (S) in the Werkzeugkavität (K) (step a) takes place. Method according to one of claims 1 to 8, characterized in that at least a part of the foaming of the foamable material (S) in step b) is carried out under the influence of an electric and / or electromagnetic field. Method according to one of claims 1 to 9, characterized in that it is the reinforcing material (VM) is a nanoscale filler. Method according to one of claims 1 to 10, characterized in that the filling of the mold cavity (K) in step a) takes place in an injection molding process. Method according to one of claims 1 to 11, characterized in that it comprises the following steps: a1) producing a structural part (ST) by means of an injection molding process, a2) filling a tool cavity (K) which is spatially connected to the structural part (ST) produced under a1, with at least one foamable material (S) and at least one reinforcing material (VM), b) foaming the foamable material (S), c) removal of the foamed molding, d) optionally further processing of the molded part. Shaped article obtainable by a process according to one of claims 1 to 12. Molding according to claim 13, characterized in that it is a molded part containing a fiber-reinforced plastic foam. Use of the molding according to one of claims 13 or 14 in trim parts.

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