DE4211446C2 - Process for producing a regenerate from fiber-containing thermosets and use - Google Patents

Description

The invention relates to a method for producing a regrind from Duroplasts impregnated or coated flat Fiber structures, the thermoset not yet is fully cured, but in one morphological intermediate state is located, as well whose Use.

When processing impregnated with thermosets Fiber structures create residues that are disposed of have to. An example of this is the production of Cutting or grinding wheels. Here, for. B. Glass fiber fabric with solutions of curable resins Soaked in phenol, and after drying at 80 to Circular discs punched out of it at 160 ° C. The Disks are made with a grinding wheel mixture  coated and cured. Because the drying process only so far that the resin is tack-free, but on the other hand not yet in the B state has passed according to DIN 16916 Part 1, the resin is in a morphological Intermediate state.

Another example are residues from Processing prepregs. The fiber fabrics are z. B. impregnated with an epoxy resin solution and dried. Due to the oven temperature, the stickiness and the Remaining gel time adjustable. The prepregs will be cut to size, placed on the mold surface and cured under pressure. Because here too the Harz is gelled but not fully cured, it is also in a morphological Intermediate state.

Another example are waste leftovers technical filter paper, for example with Phenolic resin is impregnated. It is known, hardened reinforced thermosets such as Grind up hard papers and molding compounds Add phenolic resin base as filler (Becker / Braun: Plastic handbook, Hanser publishing house, volume 10, "Thermosets"). The use of this - albeit high quality - filler leads however due to high grinding costs to make the molding compound more expensive. There already small proportions of regrind the Increase the melt viscosity of the molding compound and thus that Change flow hardening behavior leads to use  of the regrind by the molding compound processor frequently to quality problems.

The attempts to chemically digest such residues or subject to pyrolysis have so far not enforced. Especially with a high percentage on long fibers is significant process engineering problems.

From a working group of the State Working Group on Waste developed new version of the 1985 waste catalog divides the Thermoset residues in two categories: cured and uncured residues. The hardened Residues can then be disposed of like household waste, d. H. deposited in an orderly landfill or in be incinerated in a waste incineration plant. Not hardened residues, their disposal subject of this invention are to be treated as hazardous waste. They are subject to the obligation to provide evidence and are as far as possible to incinerate hazardous waste.

Since the disposal of a residual material by burning The last option is to be considered if one So reuse is not possible Task to remove the residues from with uncured Thermosets impregnated or coated Processing fiber structures so that a Reuse is possible.  

The object is achieved by the method of claim 1.

Lattices, fabrics, Scrims, wood veneers, papers and nonwovens, etc. called inorganic and organic fibers.

The regenerate does not contain fibers with a length of not more than 10 mm, preferably 0.5 to 5 mm, and one Thermoset content of 10 to 50% by weight, preferably 20 up to 40 wt .-%, based on the fiber / thermoset mixture.

The regenerate can be used as inorganic fillers Calcium oxide, aluminum oxide, stone powder u. Ä. contained depending on the intended use of the regrind.

This is the case with phenolic resin-containing residues Resin in an intermediate state between the A and B state according to DIN 16916 part 1, but is preferred non-sticky. This is the case with epoxy resin-containing residues Resin gelled and still shows a certain stickiness on.

The residues are, if they are for the subsequent Are too large, first one Subjected to pre-shredding, for example in a cutting mill can be carried out. Then the pre-shredded residues  e.g. B. in a pin mill up to fiber lengths of crushed less than 10 mm. The softer the resin in the residual materials, the more difficult it becomes Pre-crushing and especially the grinding process. Around to resolve this difficulty are invented inorganic fillers mixed in before or during grinding, because in this way a free-flowing Regenerate with a still reactive thermoset component can be produced, which also during the grinding process remains connected to the fiber material.

To resolve the difficulties with Grinding are additional given two options.

The residues can be dried further, for example the thermosets are further cross-linked, without being in the hardened state pass over. You can also by cooling below the Glass transition point can be embrittled. Then it is often necessary, however Cooling device to cool.

According to the invention but are the residues with an addition of inorganic fillers crushed the existing ones and when Powder and crush newly created surfaces prevent such a caking.

The additionally proposed methods can be used combined the inventive method depending on the degree of dryness of the Thermosets and the purpose of the regenerate. If not enough it is dried residues, for example it makes sense to start with at higher temperatures dry and then with the addition of fillers shred. This will make the responsiveness the thermosets and the flowability of the regenerate receive. Low temperature grinding has the disadvantage that the thermosets are at least partially from the fibers be separated and the regrind at the subsequent storage cakes. The  Caking can be done by adding fillers Shred or be prevented afterwards.

The regenerate can be used as a hardenable component in Molding compounds, in friction lining compounds and in refractory compounds be used. Molding compounds often contain Rock meal as filler, so that here at Crushing of the residues rock powder added will. For friction linings are barium sulfate, Magnesium oxide, zirconium oxide and aluminum oxide suitable Fillers, while refractory magnesium oxide, Contain alumina or silicon carbide.

It was surprisingly found that the morphological intermediate state The thermoset part of the regenerate the corresponding Proportion of fresh ungelled thermoset in the masses can replace without the physical Properties of the hardened made from it Body adversely change. The regenerate is So no inert filler but contributes significantly Saving of thermoset raw materials at. Through the Invention will remove residues from fibrous, uncured thermosets as  Avoiding hazardous waste and the residual materials fed meaningful reuse.

The invention is illustrated by the following examples explained in more detail without being limited to these statements to be.

Examples example 1

58 kg of punch waste from phenolic resin-impregnated Glass fiber fabrics with a resin content of 30% by weight are in a twin-screw mixer with 42 kg of chalk and 5 kg of water at a maximum temperature of 80 ° C homogenized. A plastic mass is created that broken after cooling and into granules smaller than 200 µm is ground. The regenerate is in Examples 2, 3 and 4 used.

Example 2

1.5 kg of regrind from Example 1, 3 kg of phenol novolak a melting point of 80 to 85 ° C according to DIN 16916, Part 1, 0.45 kg hexamethylenetetramine, 0.08 kg Magnesium stearate, 0.03 kg montan wax, 0.5 kg Soft wood flour, 1.5 kg glass fiber with a average cutting length of 4 mm and 2.94 kg Chalk is intimately mixed and at 100 to 130 ° C heated rollers abandoned.  

The mass increases in about 3 minutes compacted a coherent fur and homogenized. The resulting fur is in one processed usual compression molding to form. The physical values of the hardened moldings are above the minimum values of type 2 according to DIN 7708.

Example 3

12.5% by weight of regrind from Example 1, 7.75% by weight of mineral fibers, 34.0% by weight of metal chips, 21.0% by weight of rubber, 2.0% by weight are mixed in an intensive mixer. Phenolic resin, 2.5 wt .-% friction support and 20.25 wt .-% fillers mixed. The mixture is pressed in the usual way at 160 ° C and a pressure of 150 daN cm ^-2 to friction linings. The hardened and finished friction linings are tested on the test bench in accordance with programs specified by automobile manufacturers. The results are shown in the table. The hardness of the linings is measured in accordance with DIN 50103 (Rockwell hardness) at several points using a half-inch ball and a test force of 600 N. The toppings are all in the range of 40 to 80 HRR. The microscopic examinations show no changes in the structure of the deposits. The results of the endurance run over 14,000 km also show no comfort differences compared to the comparison surfaces (example 5).

Example 4

As in Example 3, a mixture of 25.0% by weight Regenerate from Example 1, 2.5% by weight of mineral fibers, 34.0% by weight of metal chips, 21.0% by weight of rubber, 2.5% by weight of friction supports and 15.0% by weight of fillers Friction linings processed. The test results are in the Compiled table. The properties of the rubbers show no significant changes from those according to Example 3, although the amount of regrind doubled and no additional phenolic resin was used.

Example 5 (Comparison to Examples 3 and 4)

As in Examples 3 and 4, a regenerate-free Mixture of 13.0% by weight mineral fibers, 34.0% by weight Metal chips, 21.0% by weight rubber, 4.0% by weight Phenolic resin, 2.5% by weight of friction supports and 25.5% by weight Fillers processed into friction linings. The Test results in the table are those of Examples 3 and 4 are compared. The properties the regenerate-free coverings show no advantages compared to those of regenerated ones.  

table

Example 6

30 kg of leftovers from resin-impregnated technical Filter paper is used in a twin-screw extruder 70 kg of chalk and 3 kg of water at a temperature of Homogenized 90 ° C. The resulting plastic mass is broken after cooling and into granules ground less than 0.5 mm. The regenerate obtained in this way is used in Example 7.

Example 7

8500 g of a mixture of various magnesites Grain is made with 1000 g of regrind according to the invention  from Example 6 and 500 g of a 70% aqueous Phenol resol (phenol formaldehyde ratio 1: 1.55) homogeneously mixed.

After pressing into moldings for the Refractory industry results in a cold pressure resistance of 89 N / mm².

The art-bound moldings are then up to one Temperature of 180 ° C heated and hardened. she then have a strength that is so great that they well transported and installed in units can. The determined cold bending strength is included the hardened moldings at approx. 20 N / mm² and thus meets the requirements of Refractory industry.

Claims (5)

1. A process for the production of a regrind by comminuting residues of most of the Duropla impregnated and / or coated in a mor phological intermediate state with flattened fiber structures, characterized in that the residues are ground in the presence of inorganic fillers, if appropriate after pre-comminution that the fiber length is less than 10 mm, the inorganic fillers being mixed with the residues before or during milling. 2. The method according to claim 1, characterized in that that the residues are additionally ge be dried without curing the thermosets, and / or below the glass transition point of the Thermosets are cooled. 3. Use of the according to claims 1 or 2 ago adjustable regrind as a curable component in Friction lining masses. 4. Use of the regenerate that can be produced according to claims 1 or 2 as a curable component in molding compounds. 5. Use of the regenerate that can be produced according to claims 1 or 2 as a hardenable component in refractory materials.