EP1727930A1

EP1727930A1 - Complex matting with a layer of volumized fibers

Info

Publication number: EP1727930A1
Application number: EP05717005A
Authority: EP
Inventors: Klaus Kölzer
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-03-22
Filing date: 2005-03-11
Publication date: 2006-12-06
Also published as: DE102004014325A1; US20070193490A1; BRPI0509143A; WO2005093144A1

Abstract

A method for the production of multilayered matting formed with the aid of fibers, filaments, threads or strong yarns; multilayered matting or a part formed according to said method; a device for carrying out said method.

Description

Complex mat with a layer of bulk fibers

The invention relates to a method for producing a multi-layer mat formed with the aid of fibers, filament threads, yarns or twists, a multi-layer mat or molded part produced in accordance with the method, and a device for carrying out the method

A fabric made of glass fibers is described in DE 203 1 0 085 U l. This fabric consists of loosely laid fibers that have not been sewn together

A multilayer mat of the type mentioned at the outset is said to have high ductility and high three-dimensional deformability if these are to be used for the reinforcement of hardenable plastics. These mats are embedded between two mold halves, for example in accordance with printing step EP 0 395 548 B1 Resins of the mold halves are brought into the open cavities of the molds by injection (pressure) or by infusion (vacuum) hardenable resins such as unsaturated polyester resins, phenol resins, epoxy resins. This results in a so-called full lambate

If the middle layer of a multi-layer mat consists of a particularly light material such as foam, then there is a so-called sandwich laminate

Basically, several individually inserted fiber layers can be used for pressing in such closed systems. However, multilayer mats are advantageously processed, as are known from the documents DE 1 00 51 598 AI and DE 1 02 1 1 1 75 C l. The workflow can be simplified in this way and be cheaper

Multi-layer mats known from the cited prior art have two outer cover layers made of cut glass fibers. In the core area there is a middle layer The individual layers of this Mats are connected to each other by a close knitting process to a multilayer mat

For the function of this multi-layer mat, it is important that the middle layer, also called middle layer or core layer, behaves elastically and is able to provide restoring tension. Then it can be achieved that this resilient middle layer reliably presses the outer cover layers onto the molds. that there is no overflow of unreinforced resin between the mold and the top layers, which would impair the functionality of the molded part. The multi-layer mat should also be stretchable, so that there is no cracking in the case of complicated shaping

Commercially available multi-layer mats include a central or core layer made of needled or felted plastic monofilaments (e.g. polypropylene, polyester, polyamide, etc.) or made of needled or loop-shaped glass fibers Loosely connected to one another This is to ensure the stretchability and deformability of the multi-layer mat and the restoring stress of the core material.At the same time, the existing restoring stress of the core material, i.e. the middle layer, creates open drainage structures that, after closing the mold, minimize ventilation and filling with liquid resin impair

However, these multilayer mats which are on the market and known from the publications DE 1 00 51 598 AI and DE 1 02 1 1 1 75 C 1, which are offered, for example, under the names ROVICORE or MULTIMAT, have the disadvantage that when used of plastic filaments for the core layer the laminate homogeneity of the finished molded part is disturbed, because these plastic filaments form a separate separating layer between the actual reinforcing fibers as a foreign body. Problems arise with regard to the strength of the molded article produced therefrom When using loop-shaped glass fibers, there is the problem that the multi-layer mat, also called complex material, compressed in the molds, due to the high material compression, results in significantly higher specific weights than is desired for most molded parts

The embodiments known from the prior art also have the disadvantage that with low compression in the mold, very high and undesirable resin accumulations occur in the core area and, when the compression is too high, the ventilation and flow rate are disadvantageously greatly reduced.

A multilayer mat is known from the publication WO 02/076701 A I, in which the volumized spin threads, yarns or twists of a middle layer formed from fibers differ in the material or the degree of volumization. In this way, good drinking and deaeration properties with low resin absorption should be achieved.

The object of the invention is to provide a multilayer mat and molded parts produced therefrom with improved properties.

To solve the task, a multi-layer mat is created, in which the middle layer comprises volumized spin threads, yarns or threads. Volumized spin threads, yarns or threads are described in DE 3540537 AI. Hollow body fillers made of plastic are embedded between fibers of spin threads, yarns or twists. In particular, the hollow body fillers are hollow microspheres which were previously blown up by supplying heat. For this purpose, the unblown precursor of a hollow body filler is introduced into the interstices between the fibers and the material obtained in this way is exposed to the temperature required for the blowing process of the preliminary stage. The diameter of the hollow body fillers is typically 20 to 300 μm. The length of the fibers, spin threads, yarns or threads used is advantageously 5-1 50 mm

In the prior art, volumization is provided in order to be able to adjust the absorption capacity for liquid hardenable resins to a desired value. In contrast to this, the aim of the present invention is to achieve and to improve the mechanical properties of a multilayer mat, in particular to ensure good elastic properties as well as restoring tensions. In particular, spinning threads, yarns or threads made of glass fibers are volumized. Spinning threads, threads or yarns formed from glass fibers are expanded by a multiple of their original volume. These are now processed into a multilayer mat with outer cover layers outer cover layers can consist of fibers, in particular glass fibers, which are connected to the central layer, for example, by a short-knitting process. However, the cover layers are also preferably formed from spin threads, yarns or twists, since there nn making it easier

Manufacturing is simple and inexpensive, with the individual layers of material being deposited in layers on a treadmill with a plurality of cutting units arranged one behind the other, and being fed to the sewing process

A disadvantage of the multi-layer mats on the market, also called complex mats, is that the needled or knitted middle layers, also called core layers, have to be produced in a separate machine work process. The multi-layer mat according to the invention can be produced in one operation on one machine A cheaper production compared to the prior art is therefore possible

It was surprisingly found that even two-dimensionally arranged facets expanded with elastic micro hollow bodies or spheres serstrαnge have a high elasticity and restoring tension and generate a high hydraulic back pressure under pressure, which is achieved by the deformation of the hollow micro-body. This back pressure is sufficient to press external, reinforcing fibers against the mold walls. In contrast to this, with the core layers on the market and described above, mechanical springback effects only occur if part of the needled or loop-knitted or knitted fibers or spin threads, yarns or twists are arranged vertically in the direction of the pressure (three-dimensionality). In contrast, in the case of the volumized spin threads, yarns or threads, the two-dimensional arrangement is surprisingly sufficient to advantageously be able to provide a high restoring tension.

A mat used as a middle layer can also be subsequently volumized. Such mats have been on the market for a long time under the name "SPHEREMAT". Because of the chemical or mechanical fixation at the crossing points, these mats do not have the desired flexibility and elasticity of loose thread threads, yarns or yarns that have been sewn together only after volumization It is therefore preferable to use such middle layers which have been prepared from spin threads, yarns or threads which have already been volumized.

With the three-dimensional arrangement of the spin threads, yarns or threads of the core or middle layer of the multilayer mats on the market ("ROVICORE", "MULTIMAT" etc.), compressive stresses are generated in the vertical direction, which lead to an unsightly surface of the finished molded part ( Print effect). If the volumized spin threads, yarns or twists of a core or middle layer are arranged two-dimensionally, this impairment of the surface of a molded part is avoided.

The embedded hollow microspheres also reduce resin consumption by up to 50% compared to the above-mentioned multi-layer mats available on the market. In contrast to this, this means a reduction in the specific weight of sometimes more than 50% the complex mats on the market.

The hydraulic reset tension of the hollow microspheres and despite the only two-dimensionally arranged tangle of the volumized spin threads, yarns or twists creates a coarse and open material structure. This leads to advantageous ventilation and resin drainage properties.

Another advantage of using very light and low-resin, volumised fiber threads, yarns or twists made of glass fibers in the core area of a multilayer mat is that the result has the characteristics of a full laminate but the weight-reducing properties of a sandwich laminate. In contrast to the sandwich laminates already on the market, no additional core material made of light wood or foam and the like has to be worked in separately if a lightweight, rigid construction is desired for structural reasons.

Both the core layer or middle layer and the cover layers or cover layers advantageously consist of glass fibers. This makes it possible to achieve an unprecedented homogeneity of the product. The physical-mechanical properties of the middle layer then correspond to the physical-technical properties of the cover layers.

Figure 1 shows a section of the central position in a top view and Figure 2 shows a section of the central position from a perspective. Spherical hollow bodies 2 are embedded between individual glass fibers 1. The spaces 3 can be filled with impregnating resins. Figure 3 shows schematically the structure of a multilayer mat. Two cover layers 5 and 6, which consist of non-volumized glass fibers, enclose a middle layer 4, which is formed from volumized spin threads consisting of glass fibers. The fibers in the top layers 5 and ό and in the middle layer 4 run parallel or at least almost parallel to the surface 7 and are arranged two-dimensionally in this sense. he manufactured, shown schematically in Figure 3 complex mat from cut fibers with a cutting length of 5 - 200 mm. The various layers have been connected to each other through a close-knit process. The outer layers 5 and 6 consist of cut glass fibers and the middle layer 4 of volumized, cut spin threads which have been formed from glass fibers. The core layer 4 can consist of a mixture of volumized spin threads, yarns or twists and non-volumized glass fibers. For the volumized layer 4, fibers based on carbon, aramid, plastic fibers have been found to be particularly suitable. The outer layers 5 and 6 then preferably consist of aramid or carbon fibers. The spin threads of the middle layer are cut after volumizing and then connected to the cover layers by a sewing process.

An apparatus for performing the method is shown schematically in FIG. 4. Above a treadmill 8, three cutting units 9, 10 and 11 are arranged one behind the other. So-called endless filaments that are not volumized are fed to the outer cutting units. Volumized endless filaments are fed to the central cutting unit 1 0.

A continuous thread is one that is very long and is usually unwound from a bobbin for processing. Such an endless thread can be several tens of meters to several hundred meters long.

The cutting units cut spin threads of the desired length from the continuous spin threads. The cut threads arrive on the treadmill 8 underneath. The treadmill 8 transports the cut spin threads, which are layered one above the other, to a device 1 2 which sews the spin threads together. The mat shown in FIG. 3 is then the result.

Claims

Expectations

1 . Method for producing a mat, comprising the steps: - providing a layer (4) which comprises volumized spin threads, yarns or threads (1, 2), - providing at least one further layer (5, 6) formed from fibers, - connecting the Layers (4, 5, 6), preferably by sewing.

2. The method according to claim 1, in which non-volumized and volumized spin threads, yarns or threads are layered one above the other, preferably on a treadmill and then the layers (4, 5, 6) are sewn together.

3. The method according to the preceding claim, in which the fibers or spin threads, yarns or twists formed therefrom are deposited by cutting off continuous fibers, continuous spin threads, continuous yarns or continuous twists.

4. The method according to claim 1, 2 or 3, wherein the layers (4, 5, 6) are formed by fibers, spin threads, game or yarns, which are arranged parallel to the surface (7) of the mat.

5. The method according to any one of the preceding claims, in which the fibers, spin threads, yarns or threads provided for the layer structure are 5 to 200 mm long and / or the hollow micro-bodies used for the voluization have an average diameter of 20 to 300 μ exhibit.

6. The method according to any one of the preceding claims, wherein the middle layer and top layers are formed from glass fibers.

7. The method according to any one of the preceding claims, wherein the mat is brought into a mold and brought into the mold hardenable resins for producing a fiber-reinforced molded part become.

8. Mat can be produced by a method with the features according to one of the preceding claims, comprising a middle layer of volumized spin threads, yarns or twists as well as cover layers of non-volumised fibers which are sewn together

9. Mat according to the preceding claim, in which the fibers, spin threads, yarns or threads are arranged parallel to the surface (7).

1 0. Mat according to one of the two preceding claims, in which the fibers, spin threads, yarns or threads are formed exclusively from glass fibers.

1 1. Device for producing a mat according to one of the three preceding claims, consisting of three cutting units (9, 10, 11) arranged one behind the other, which are arranged above a treadmill (8), and means for sewing (1 2) of cut fibers, spin threads, yarns or twists deposited on the treadmill (8) and coming from the cutting units (9, 10, 11). 2. Device according to the preceding claim, in which volumized spin threads, yarns or threads are fed to the cutting unit arranged in the middle and non-volumized spin threads, yarns or threads are fed to the other two cutting units.