DE102007037680A1 - Process for production of injection molded structural components reinforced with endless fibers, generally useful in production of injection molded components is cost effective and permits high degree of geometric variability - Google Patents

Abstract

Process for production of injection molded structural components (20) reinforced with endless fibers, based on a thermoplastic workpiece material involving: preparation of a workpiece mold comprising a die (10) and punch (16), where the workpiece mold has a series of holes in the region of the punch and/or die, introduction of needles (3) (sic) into the open mold space, addition of semifinished endless fiber thermoplastic prepregs (sic) or hybrids, so that these are held by the needles, closing of the workpiece mold, and injection of a thermoplastic workpiece material, e.g. polypropylene or polyamine, followed by cutting back (sic) of the needles. An independent claim is included for a workpiece mold.

Description

The The invention relates to a process for the preparation of a partial Continuous fiber reinforced injection molded component based on a thermoplastic material and a mold, the suitable for this method.

injection molding components are used in the automotive industry in a wide variety of areas. You can use complex geometries, different Wall thicknesses as well as excellent surfaces and different material combinations are produced. The Injection molding is a very cost effective and fast manufacturing process for the production of a Variety of serial components in large quantities.

Unreinforced Thermoplastics often have insufficient strength and stiffness properties. It is therefore known that the thermoplastic short or long fibers, for Example in the form of glass fibers, add. Compared to components Steel or aluminum but also have the short or long fiber reinforced Injection molded components a significantly lower rigidity and strength. It is therefore still known, the components partially directed with Reinforce continuous fibers. Such continuous fiber reinforcements For example, they may be woven, laid, knitted, or the like.

to Production of components from thermoplastic, continuous fiber reinforced Plastics are known various methods.

DE 42 15 756 A1 describes a process for the production of hollow bodies after the so-called melt-pressure molding, in which a thermoplastic core tube is coated with fibers, thermoplastic prepregs or hybrid fibers. In the case of rotationally symmetrical components, fiber deposition takes place in the winding process. The preform thus produced is heated from the outside and then placed in a mold, sealed pressure-tight and subjected to internal pressure, which causes the consolidation of the matrix material.

EP 08 35 745 A2 describes a method for the production of tubular hollow bodies in which first a thermoplastic core tube is wound with fibers. In the wound hollow profile, a conically shaped mandrel is introduced whose cross-section is geometrically similar to the hollow profile. Subsequently, the tubular hollow body is completely or partially melted, wherein a portion of the inner layer of the tubular hollow body forming thermoplastic material is pressed into the fiber layer and thus forms a fiber reinforced outer layer of the hollow body.

DE 43 00 208 A1 discloses a method for producing hollow bodies, in particular tubes, tubular torsion bars and pressure vessels made of fiber-reinforced plastics, in which at least two layers with fibers oriented differently from the longitudinal direction are incorporated. The wound tube is placed in a tool and placed with the tool in a rotational movement about the tube longitudinal axis. The thermoplastic core tube is heated to temperatures above the melting temperature and the centrifugal forces generated by the rotational movement act on the thermoplastic melt, thus creating the consolidation pressure.

DE 101 06 923 A1 describes a method for the production of injection molded components from thermoplastic continuous fiber reinforced plastics, in which a core covered with continuous fibers is introduced into a mold, plastic in liquid form is introduced into the mold space substantially perpendicular to the fibers and the introduced plastic is cured under pressure. The continuous fibers are used as prepegs or hybrid fibers. The liquefied plastic is fed with a common injection molding machine.

Of the Invention is based on the object, a cost-effective Manufacturing process for the production of injection molded components provide partially reinforced with continuous fibers are. The manufacturing process should be suitable for large-scale use suitable and high variability in geometry and design allow the injection molding. In this case, in particular, a location and orientation of the continuous fibers defined in the injection molding pretend.

• (a) Bereitstellen einer aus zumindest Matrize und Patrize bestehenden Werkzeugform für das Spritzgießverfahren, wobei die Werkzeugform im Bereich der Matrize und/oder der Patrize eine Vielzahl von Durchgangsbohrungen aufweist, in denen jeweils eine Nadel angeordnet ist, die in Lage und Abmessungen so ausgelegt ist, dass sie dichtend in der Durchgangsbohrung liegt und durch die Durchgangsbohrung in einen Formraum der Werkzeugform ein- und ausfahrbar ist;
• (b) Einfahren von Nadeln in den Formraum der offenen Werkzeugform bis die Nadeln eine Position erreicht haben, die für das Einlegen eines Endlosfaserhalbzeugs geeignet ist;
• (c) Einlegen des Endlosfaserhalbzeugs aus thermoplastischen Prepregs oder Hybridgarn, derart, dass es von den Nadeln gehalten wird;
• (d) gegebenenfalls Ein- oder Ausfahren der Nadeln, bis das Endlosfaserhalbzeug eine Position erreicht hat, die weitgehend einer Lage der Endlosfasern im fertigen Spritzgussbauteil entspricht;
• (e) gegebenenfalls Wiederholen der Schritte (b) bis (d), wenn zwei oder mehr Endlosfaserhalbzeuge zu positionieren sind;
• (f) Schließen der Werkzeugform; und
• (g) ein- oder mehrseitiges Einspritzen eines verflüssigten thermoplastischen Werkstoffs und Zurückfahren der Nadeln aus der Werkzeugform.

According to one aspect of the invention this object is achieved by the method for producing a partially reinforced with continuous fibers injection molding component based on a thermoplastic material according to claim 1. The method comprises the steps:

• (A) providing an at least die and male mold for the injection molding process, wherein the mold in the region of the die and / or the male has a plurality of through holes, in each of which a needle is arranged, which is designed in position and dimensions in that it lies sealingly in the through-hole and can be retracted and extended through the through-hole into a mold space of the mold;
• (b) inserting needles into the mold cavity of the open mold until the needles have reached a position suitable for loading a continuous fiber blank;
• (c) placing the continuous fiber semi-finished product of thermoplastic prepreg or hybrid yarn such that it is held by the needles;
• (d) optionally retracting or extending the needles until the continuous fiber semi-finished product has reached a position which substantially corresponds to a position of the continuous fibers in the finished injection-molded component;
• (e) optionally repeating steps (b) to (d) when two or more continuous filament semi-finished products are to be positioned;
• (f) closing the mold; and
• (g) single or multi-sided injection of a liquefied thermoplastic material and retraction of the needles from the mold.

With Help of the procedure it is possible for the first time, in the large-scale Use and with high variability in position and orientation the continuous fibers and in the design of the injection molded component to the production shape. The new manufacturing process leads to so-called thermoplastic hybrid structures made from inexpensive Materials exist and in medium to large series are economically producible. As an economical manufacturing process finds the injection molding application, with the unreinforced and glass fiber reinforced components can be produced, the in highly stressed areas with directional endless fiber inserts be strengthened. The injection molding component is formed during the molding process simultaneous consolidation of continuous fiber semi-finished products Savings in process steps are achieved and synergy effects by combination of thermoplastic injection molding and modern fiber composite technology can be used. The advantages of the invention are among other things in the cost-effective provision of Materials and tools, the mass-produced automated Production, short cycle times, low storage costs, there no cooling, material separation and air cleaning and Extraction plants are required, and in the low-emission manufacturing.

When Endless fibers for the process according to the invention can be natural and synthetic fibers on Carbohydrate or amino acid base, carbon fibers, glass fibers, Aramid fibers, ceramic fibers such as silicon carbide, boron nitride and Silicate fibers, polyether ketone fibers, wholly aromatic polyamide, Polyethylene, polypropylene, polybutylene terephthalate, polyamide, polysulfone, Polyethecketon and any combination of the previous ones be used.

thermoplastic Materials that are suitable for the purposes of the invention Suitable process include, in particular modified natural substances, such as Cellulose nitrate, cellulose acetate, cellulose ethers and cellulose mixed ethers, Polyamides, polycarbonates, polyesters, polyphenylene oxides, polysulfones, Polyvinyl acetals, polyolefins, ionomers, polyvinyl chloride (PVC), Polyvinylidene chloride, polymethylmethacrylate, polyacrylonitrile, polystyrene, Polyacetals, fluorinated plastics, polyvinyl alcohol, polyvinyl acetate, Poly-p-xylylene, polyether ketones, acrylonitrile-butadiene-styrene copolymers, Styrene-acrylonitrile copolymers, polyterephthalates, linear polyurethanes and chlorinated polyethers.

Continuous fiber semi-finished products are fabrics, scrims, knits or the like made of continuous fibers and a thermoplastic matrix. The continuous fiber semi-finished product usually consists from 10-90 volume percent of continuous fibers and 90-10 Volume percent of the thermoplastic matrix. The thermoplastic Matrix consists in particular of the aforementioned thermoplastic Materials. Prepregs are a relatively coarse one Thread of endless material with a thousand or more filaments, the pre-soaked with a melt or a powder of the matrix material is. Hybrid yarns include continuous fiber filaments and matrix filaments, which are distributed homogeneously over the yarn cross section. The production of continuous fiber semi-finished products is known from the prior art and continuous fiber semi-finished products are commercially available from different suppliers available. It is also conceivable, pure reinforcing semi-finished fiber to use.

in the Step (a) of the process becomes an at least die and patrix existing mold for the injection molding process provided. The mold has in the area of the die and / or the male part has a plurality of through holes. In every Through hole is a needle arranged in position and dimensions is designed so that it lies sealingly in the through hole and through the through hole in a mold cavity of the mold can be moved in and out. To execute the movement can the needles appropriate actuators are assigned, the individual Needles, groups of needles or all needles at the same time according to specifiable Can operate scheme. A number of needles is preferably in the range of 2 to 100 needles per mold. Preferably, the needle has a cylindrical basic shape and a Contour of the needle tip is designed so that it retracts into Position of the needle of a contour of the tool wall in the area of Form space follows. In other words, the needle can be aligned with Tool wall be withdrawn, leaving a smooth Component surface is created and post-processing of the injection molded component can be dispensed with. Such a mold is not known from the prior art and provides another Aspect of the invention.

The needles are moved in step (b) so far in the mold until the needles have reached a position that is suitable for the insertion of a Endlosfaser semi-finished is suitable.

in the Step (c), the continuous fiber semi-finished product is inserted so that it from the needles is held.

in the Step (d), if necessary, the needles are retracted or extended, until the continuous fiber semi-finished product has reached a position that is largely a position of the continuous fibers in the finished injection-molded component corresponds. This is always necessary when the position for inserting the Endlosfaserhalbzeugs and the desired position of the continuous fiber semi-finished in do not match to be manufactured injection molded part. So It is usually advantageous to insert the needles of the continuous fiber semi-finished product over the subsequent layer extend the reinforcing material addition. All in all So is a positioning and fixation of the continuous fibers in the tool shape achieved by the needles, so that the fiber orientation also during the subsequent subsequent injection process persists. In addition to the pincushion can for further Improvement of the fiber fixation in the later component Tentering frames are used for the continuous fiber semi-finished product. An advantage of the needles according to the invention over the Use of a tenter frame but is that on a subsequent Trim of the continuous fiber semi-finished product can be dispensed with.

in the Step (e), steps (b) to (d) are optionally repeated, when two or more continuous fiber semi-finished products are to be positioned. For example, it is conceivable that various continuous fiber semi-finished products be placed next to each other or overlapping. The Method is suitable in this context, in particular for the production of injection molded parts, in which between two layers of continuous fibers a base made of a thermoplastic material is arranged (hereinafter referred to as sandwich injection molded part). For this purpose points the tool shape both on the side of the die and on sides the male corresponding through holes and needles, with their Help each on the inner walls of the die respectively Patrize continuous fiber semi-finished products are positioned. The continuous fiber semi-finished products So they support themselves on the wall of the matrix and the patrix and are fixed by the needles. Subsequently, the thermoplastic material between the two layers of continuous fiber semi-finished product injected.

in the Step (f) the mold is closed, usually such that the male or female is applied to the needles and between Needles and tools no longer exists, through which the Continuous fiber semi-finished product could slip from the needles.

Subsequently becomes in step (g) one or more pages a liquefied injected thermoplastic material and the needles are afterwards moved back from the mold. The liquefied thermoplastic Material can therefore at several points simultaneously or in time be injected offset. It is also conceivable, the injection in several, separated by cooling manufacturing steps To perform: After cooling the first injected thermoplastic material is another Injection. In this way, for example, injection molded parts manufactured with areas of different thermoplastic materials become. It is by means of the mentioned procedure especially possible to produce an injection-molded component, having an internally disposed continuous fiber reinforcement, the is enclosed by two layers of thermoplastic. This two-sided Material allocation is particularly appropriate when outer skin components for Vehicle parts are to be finished, with on the one hand a decorative Layer and on the other side a scratch-resistant layer, for example based on a paint, is injected.

Preferably is the to be manufactured injection molding component after step (g) and during a cooling process of the injected Material compressed by nozzle Nachdruck and / or pressing pressure. After retracting the needles from the mold in Step (g) thus solidifies the injected layer while retaining a nozzle Nachdrucks and / or application of a pressing pressure. The molten thermoplastic matrix of the continuous fiber semi-finished product as well as the injected thermoplastic material consolidate under pressure and make a firm connection. It's mostly necessary, the material shrinkage of the thermoplastics during to compensate for the cooling by the tool halves continued to contract during the cooling process and thereby the cavity is reduced. This Manufacturing process is also referred to as injection-compression molding. To get the best possible connection of the continuous fiber semi-finished products to ensure the thermoplastic material the thermoplastic materials may be the same or miscible. The Injection embossing improves the cohesion between the continuous fibers and the injected thermoplastic material and injection-compression molding are very small wall thicknesses with high quality surfaces produced.

In the aforementioned method variants, it is also conceivable two or several times from the same page with different materials inject. For example, if first a soft component and Based on this, a hard component is injected Components are manufactured with soft-touch effect (for example Instrument panels with local continuous fiber reinforcement in the airbag area).

Furthermore additional inserts (so-called inserts, For example, wrapped steel inserts), clips or other fasteners with molded and directly with the continuous fiber semi-finished or positively connected. That way you can realized high-strength force transmission in injection molded components and thus manufactured highly integrated, multifunctional structural components become.

The Invention will be described below with reference to an embodiment and the accompanying drawing explained in more detail. Show it:

1 to 7 the process scheme according to the invention for encapsulation of continuous fiber reinforced semi-finished by injection molding in different production steps and in a schematic diagram.

1 shows parts of a tool mold that can be used to make continuous fiber reinforced injection molded components. The mold includes a die 10 , a patrix 16 and a needle attachment 12 with a variety of needles 13 , The patrix 16 has in its wall facing the cavity a plurality of through holes, through which the needles 13 of the pincushion 12 can be performed. In the in 1 The partial step shown in the process become the needles 13 retracted into the mold cavity until they lie approximately in the position with their ends for inserting a continuous fiber semi-finished product 14 suitable is ( 2 ). After inserting the continuous fiber semi-finished product 14 become the needles 13 pulled back until approximately the position is reached, which corresponds to the later position of the continuous fiber in the injection-molded component to be manufactured ( 3 ). For the execution of the movement of the needles 13 is used here, not shown, controllable actuator.

The continuous fiber semi-finished product 14 is now so in the of the matrix 10 given shape space inserted that from the pincushion 12 held in position and fixed ( 3 ).

After inserting the continuous fiber semi-finished product 14 the mold is closed. The matrix 10 lies in the closed state of the tool mold at the ends of the needles 13 at.

Subsequently, using a first extruder 22 an injection molding a liquefied, thermoplastic material from the side of the die 10 injected via two nozzle openings. This is the continuous fiber semi-finished product 14 into the mold side of the male part 16 pressed and supported there.

After injection of the thermoplastic material, the pincushion becomes 12 moved back from the mold and the thermoplastic material solidifies by cooling. At the same time, however, the blank is 18 further compressed by jet pressure and / or pressure during cooling to ensure consolidation of the continuous fiber with the thermoplastic material ( 4 ).

The tool is now extended so far that a second layer from the side of the male 16 from a second extruder 24 can be injected ( 5 and 6 ).

If it is again a thermoplastic material, then (as shown), the cooling process is carried out under simultaneous nozzle pressure and pressing pressure ( 7 ).

Thereafter, the tool is opened and the finished injection-molded component 20 taken. In initial tests, injection-molded components made of continuous-fiber-reinforced polypropylene (PP) or polyamine (PA) with good laminate quality could be produced.

10

die

12

pincushion

13

needles

14

Endless semi-finished fiber

16

punch

18

blank

20

injection-molded component

22 24

first and second extruder

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4215756 A1 [0005]
• - EP 0835745 A2 [0006]
• - DE 4300208 A1 [0007]
• - DE 10106923 A1 [0008]

Claims (4)

Process for producing a partially continuous fiber-reinforced injection-molded component ( 20 ) based on a thermoplastic material, comprising the steps: (a) providing at least one template ( 10 ) and patrix ( 16 ) existing mold for the injection molding process, wherein the mold in the area of the die ( 10 ) and / or the patrix ( 16 ) has a plurality of through holes, in each of which a needle ( 13 ) is arranged, which is designed in position and dimensions so that it lies sealingly in the through hole and through the through hole in a mold space of the mold and retractable; (b) Retracting Needles ( 13 ) into the mold cavity of the open mold until the needles ( 13 ) have reached a position suitable for the insertion of a continuous fiber semi-finished product ( 14 ) suitable is; (c) inserting the continuous fiber semi-finished product ( 14 ) of thermoplastic prepregs or hybrid yarn, such that it is separated from the needles ( 13 ) is held; (d) optionally retracting or extending the needles ( 13 ) until the continuous fiber semi-finished product ( 14 ) has reached a position which is largely a position of the continuous fibers in the finished injection-molded component ( 20 ) corresponds; (e) if necessary, repeating steps (b) to (d) if two or more continuous fiber semi-finished products ( 14 ) are to be positioned; (f) closing the mold; and (g) single or multi-sided injection of a liquefied thermoplastic material and retraction of the needles ( 13 ) from the mold. Method according to Claim 1, in which the injection-molded component to be manufactured ( 20 ) is pressed together after step (g) and during a cooling process of the injected material by jet printing and / or pressing pressure. Mold for injection molding, consisting of at least die ( 10 ) and patrix ( 16 ), wherein the tool mold in the region of the die ( 10 ) and / or the patrix ( 16 ) has a plurality of through holes, in each of which a needle ( 13 ) is arranged, which is designed in position and dimensions so that it lies sealingly in the through hole and can be retracted and extended through the through hole in a mold space of the mold. Tool mold according to claim 3, wherein the needle ( 13 ) has a cylindrical basic shape and a contour of the needle tip is designed so that in the retracted position of the needle ( 13 ) follows a contour of the tool wall in the region of the mold space.