WO1994003315A1

WO1994003315A1 - Process for separating plastics/non-metal composite systems

Info

Publication number: WO1994003315A1
Application number: PCT/EP1993/001956
Authority: WO
Inventors: Joachim Wagner; Werner Rasshofer; Marc Herrmann
Original assignee: Bayer Aktiengesellschaft
Priority date: 1992-08-04
Filing date: 1993-07-22
Publication date: 1994-02-17
Also published as: DE4322298A1

Abstract

jp931128s is disclosed for separating asymetrical plastics/non-metal composites, preferably coated, foamed composite components consisting of a massive, incompressible non-metal layer (4) and possibly several expansible, possibly foamed plastic layers (5), so that a plastic powder (7) is produced. The separating process is carried out in a cylinder mill with paraxial cylinders which rotate in opposite directions at different speeds, and between which is set a gap (10) whose width corresponds to the thickness of the non-metal layer (4). The non-metallic layer rests on the cylinder that rotates more slowly (2) and the ratio between the circumferential speeds of both cylinders is selected so as to be larger than one plus the quotient of the breaking elongation of the plastic material in % by the number 100.

Description

Process for the separation of plastic-non-metal composite systems

The present invention relates to a novel method for the separation of asymmetrical plastic-non-metal composites, in particular composites, which consist of a non-metal - usually with high tensile strength - and an optionally compressible plastic layer - usually with low tensile strength and high elongation at break and in which the plastic layer is separated from non-metal using shear forces. As a rule, the use of the method according to the invention also involves a shredding of the partner in the asymmetrical plastic-non-metal composite, which has the lower tensile strength.

The material recycling of components, especially those in which material composites are used, has become very important in recent years for ecological reasons. Of particular interest in this context are composite systems in which at least one of the components is a valuable substance. Composites of the type described above exist e.g. from a cover and the enclosed material, which is usually present in a higher volume fraction.

An example of the aforementioned type are soft-foam foam seats ("foam-in-cover") which are surface-coated with textiles, in which the soft-foam foam is connected to the textile after intended use and this material has to be removed in a cost-intensive manner before the foam can be used effectively . Such waste falls e.g. in large quantities when dismantling motor vehicles; The planned systematic dismantling of used motor vehicles in the future will then provide very large amounts of such waste.

Such waste is also to be expected in the disposal of upholstered furniture, mattresses and other coated molded or block foam molded articles, where other materials, such as leather or PVC foils, can also be used as covers, covers or covers. Another example of the aforementioned type are textile, one-sided coated flat products such as carpets, carpets and other floor coverings. Here, too, a mixture of different materials is generated during disposal, which cannot be recycled without separating the components from further use.

Up to now, the expert has only known the possibility of depositing, incinerating or incinerating such mixed waste, which is time-consuming and usually manual. The manual separation of goods after intended use, e.g. Hospital mattresses and old seats, possibly also a hygiene problem for the recycling company.

It is also known to comminute such composites in granulators and to separate the comminuted material in wind or gravity classifiers or by floating-sinking methods; in this case, however, a mixed fraction of the unraveled composite is obtained, since the seam surface of the materials in the composite is not deliberately separated.

Methods for cutting rigid composites are known; for example the bark of tree trunks removed by milling; here it is assumed that both materials to be cut have a certain rigidity in order to be machinable in a machining process such as a milling process. Extremely strong cooling to liquid nitrogen temperatures can also make brittle elastomeric materials and thus make them accessible for machining; it is therefore conceivable to cool the composites described above to temperatures of the liquid nitrogen and then to separate the composites using a milling process. However, because of the high need for liquid nitrogen, this process is very energy-intensive and therefore not economical.

Furthermore, in a material composite of high-strength materials, separation can be carried out by tearing off one of the two composite partners. For the above-mentioned problem of separating composites that consist of a non-metal - usually with high tensile strength - and an elastic, possibly compressible plastic layer - usually with low tensile strength and high elongation at break - all of the methods described cannot be used.

It was therefore an object of the present invention to provide a method in which the above-described disadvantages of the prior art are avoided and the prior art is also enriched in an advantageous manner.

The division and removal of highly elastic material, i.e. material with considerable elasticity and compressibility is neither possible by grinding nor by machining since the material evades the grinding pressure or is taken along by the cutting tool under stretching until the elongation at break is exceeded. The break then occurs at a point in the material that is not geometrically related to the cutting tool, but must be assigned to inhomogeneities, pre-damage and other defects in the material. In order to achieve a geometrically defined fracture formation, it seems necessary to transfer locally inhomogeneous elongation forces to the material in order to limit the location at which the elongation at break is exceeded to the desired fracture geometry.

It has now been found that by introducing the elastic material between two axially parallel rollers with a small distance ("nip"), which rotate in opposite directions at different peripheral speeds, in the immediate vicinity of the surface of the roller with the greater peripheral speed and parallel to it Zone of highly inhomogeneous expansion forces is formed, which occurs at sufficiently different peripheral speeds of the rollers to form fractures along the contact surface between the elastic material and the roller with a greater peripheral speed, so that a fine powdery removal occurs from the elastic material. Due to the compression of the elastic material when entering between the rolls in front of the roll nip, such a tension state forms in the elastic material (the material is pressed out of the roll nip against the direction of insertion into the roll nip) that the area of highly inhomogeneous expansion forces into the immediate area Near the surface of the roller is limited with greater peripheral speed. This state of tension of the elastic material ensures that the material is carried along by the roller at a lower peripheral speed, ie the speed of entry of the material into the gap corresponds to the peripheral speed of the slower roller. There is no material removal on the roller at a lower peripheral speed. It is therefore possible to separate flat composite materials in this way.

The present invention accordingly relates to a process for the separation of asymmetrical plastic-non-metal composites, preferably coated, foamed composite components, consisting of a solid, non-compressible non-metal layer and (optionally several) expandable, optionally foamed plastic layers, with recovery a plastic powder, characterized in that the separation process is carried out in a roll mill, in which the rolls are arranged parallel to the axis, rotate in opposite directions and at different speeds, in which a roll gap is set, the width of which corresponds to the thickness of the non-metal layer and at which the non-metal layer rests on the slower rotating roller and the ratio of the peripheral speeds of the two rollers is chosen to be greater than one plus the quotient of the elongation at break of the plastic material in% and the number 100.

Preferably, the ratio of the peripheral speeds of the two rollers should exceed a value of 1.5 to 2.0, based on one plus the quotient of the elongation at break of the plastic material in% and the number 100.

The ratio of the peripheral speeds of the two rollers should particularly preferably have a value in the range from above 2, preferably above 4, based on one plus the quotient of the elongation at break of the plastic material in% and have the number 100.

The peripheral speed of the roller with a lower peripheral speed can be in the range from 1 to 15 m / min, preferably 2 to 8 m / min.

In particular, the invention solves the problem of separating composite materials with pulverization of the stretchable composite component, in which the composite component to be pulverized has an elongation at break of above 50%, in particular above 100%, since other methods do not, or only accept considerable disadvantages, to achieve this object eg cryogenic processes) are available.

The method according to the invention is particularly suitable for separating composites from flat coatings made of fabrics, plastic films and leather with polyurethane foams, in particular flexible polyurethane foams, with the production of a polyurethane foam powder.

The invention is explained in more detail with reference to the accompanying Fig. 1: The composite material 3, consisting of a stretchable material 5 and a coating 4, is inserted in the direction of arrow 9 in the gap 10 between the axially parallel rollers 1 and 2, such that the Coating 4 is applied to the roller 2 at a slower peripheral speed. The direction of rotation of the rollers 1 and 2 is indicated by the arrows 11 and 12.

When entering the nip, the stretchable material 5 is compressed. The dashed lines 6 indicate the force field lines as they are formed due to the compression.

The stretchable material 5 is carried along the contact surface with the roller 1 at a greater peripheral speed. Due to the competition of this "entrainment" with the compression movements (field lines 6), highly inhomogeneous expansion forces occur which lead to breakage in the immediate vicinity of the surface of the roller 1 in the area of the curly bracket. Above a certain ratio of the peripheral speeds of the two rollers, a finely divided powder 7 with particle sizes between 50 and 500 microns. If the ratio of the circumferential speeds is less than 1 plus elongation at break of the material to be pulverized divided by 100 (1 + elongation at break / 100), a sufficiently inhomogeneous thin zone of expansion does not occur, but irregular tear products are formed in the gap.

According to the invention, the flat coating structure is obtained essentially undamaged.

As a rule, the flat coating will have comparatively high tensile strengths compared to the stretchable material, typically above 5 MPa, in particular above 10 MPa.

Furthermore, the above-mentioned non-metal layers can have additional one- or two-sided coatings for finishing e.g. as a vapor barrier, odor barrier or barrier against passage of bacteria. Is there a vapor barrier e.g. from an aluminum foil, so this should be included in the term non-metal layer, as long as the layer is sufficiently flexible.

Plastic layers in the sense of this invention are all materials with significantly lower tensile strength and higher extensibility compared to the non-metal layers in the composite, which may have elastic properties and may additionally be compressible.

Examples of this are largely open-cell flexible PUR foams which have a tensile strength in the range from 0.04 MPa to 0.5 MPa and an elongation at break of 50% to 300%. The bulk densities of these materials are in the range below 500 kg / m ³ , so that these materials have considerable elastic compressibility. Further examples are an EPDM heavy layer on the back of a carpet, which have a tensile strength in the range of around 2.5 MPa and an elongation at break of approx. 270%. This material is solid, but due to its elasticity it shows a certain amount of pressure deformation. Complex, three-dimensional moldings, for example covered or coated on all sides, can be brought into a shape by sawing and / or cutting before use of the method, which have the asymmetrical composite structure required for the method and which bring the material to be removed to the surface.

Any machine in which two or more rolls form a nip or several nips and the rolls can rotate in opposite directions at different speeds can be considered as a roll mill for this process. Such machines are known as mixing units from polymer processing, in particular rubber and PVC processing. The different speeds of the individual rollers are realized via separate gears or individually controllable motors. Roller systems of the aforementioned type are commercially available; for example, they can be obtained from Berstorff, Hanover, Germany.

The clearance between the two rolls can be adjusted mechanically and / or hydraulically in these machines and is adjusted in the method according to the invention to approximately the thickness of the non-destructively separable non-metal layer. The layer of plastic to be separated, which is less strong than the non-metal layer, is then forced through an effective gap, which is very small compared to the actual roller gap - consisting of a roller and the comparatively firm non-metal layer.

The separation process according to the invention becomes particularly effective when the speed ratios clearly exceed values of 2, preferably 4, based on one plus the quotient of the elongation at break of the plastic material to be removed in% divided by 100.

The individual rollers of such roller systems can generally be tempered, ie they can be heated or cooled. When the method according to the invention is carried out, the rolls are generally not heated separately; that when separating the plastic-non-metal composites due to the friction Excess heat generated in particular when the roller is rotating faster is possibly dissipated by cooling the rollers. When carrying out the method according to the invention, it is advantageous to keep the faster rotating roller at a temperature of 60 ° C. to 120 ° C., preferably 60 ° C. to 100 ° C. As a rule, this temperature is set automatically by carrying out the method; only a further increase in temperature has to be avoided by cooling the roller.

It may be advantageous, but not an exclusive process feature, to provide the faster rotating roller with an etched, finely corrugated or microstructured surface in order to increase the grip of this roller.

According to the method according to the invention, the asymmetrical plastic-non-metal composites to be separated are not necessarily pre-shredded, but can - e.g. in the case of production waste of carpet materials - even directly e.g. are introduced into the roller mill in this flat form from a roll. The separated flat coatings can then be rolled up again directly on a roll and the separated materials are used for further material recycling in the form of chips, flakes, powders or other small and very small parts as are directly obtained when using the method according to the invention .

Thus, it is a preferred application of the method according to the invention to use this method to free the covered soft molded foam parts from the covers, to recycle the covers for further material recycling, and to remove the soft molded foam, for example in the form of powders, which was previously used in material recycling methods described in the literature for PUR materials, such as regrind, extrusion, adhesive presses, thermoplastic processing and chemolytic processes. example

In the examples described below, work was carried out on a laboratory roller system of the type SK 6612 from Berstorff, Hanover, FRG. This machine has two fixed rollers with a circumference of 62 cm and a length of 45 cm that can be controlled independently in the speed range from 7 to 31.5 rpm. the roll gap can be reduced to less than 0.1 mm.

A plastic-non-metal composite consisting of the non-metal: fiber fabric with a layer thickness of 0.4 mm and the plastic: PUR soft foam with a layer thickness of 0.8 cm was made on the roller system described above, with the following parameters:

Circumferential speed of the roller 1: 15.0 m / min

Circumferential speed of the roller 2: 2.5 m / min

Roll gap: 0.15 mm

Roll temperature 1: 75 ° C Roll temperature 2: 30 ° C

was operated, introduced across the board. The fabric covering had a tensile strength of 43 MPa and an elongation at break of 30%; the flexible PUR foam had a tensile strength of 0.25 MPa and an elongation at break of 180%.

The fabric cover faced the slowly rotating roller during this processing step. After the composite had passed through the roll nip twice, the fabric covering could be removed in a flat form, while the flexible PUR foam was stripped off the roll as a powder.

This powder was analyzed for its particle size distribution. This resulted in an average particle size of 0.23 mm.

The particle size distribution was measured using the Malvern Particle Sizer, Model 2600, from Malvern, UK. This meter is working on the basis of light diffraction spectroscopy in the particle size range from 1 μm to approx. 1 mm.

The powdery samples were stirred into water for measurement and dispersed for approximately 60 seconds using ultrasound (XL device from Branson, Hilden, Germany). The specified average particle sizes are the particle size (= diameter of the same-mass sphere) in which 50% of all particles are smaller and 50% of all particles are larger than the specified value.

Polyurethane powders, in which 90% by weight of the particles have a particle size of less than 0.5 mm in diameter (spherical mass), as are obtained by the process according to the invention, are outstandingly suitable for modifying inorganic building materials, in particular during production of hydraulic, latent hydraulic and non-hydraulic inorganic building materials such as concrete, screed, (hydraulic) mortar and plaster.

It is known that inorganic materials such as concrete and gypsum, or the building materials made from such basic materials, are modified with polymers in order to improve the processing and use properties. For this purpose, specially developed plastics are generally used, which are very expensive due to their production. When modifying concrete, a distinction is made between chemically and physically effective concrete admixtures. Chemically active products influence cement hydration, physically active products influence the phase boundaries between the mixing water and the solids.

The PUR powders used according to the invention obviously act both as chemically and as physically active products.

The inorganic building materials modified with PUR powders produced in this way show:

lower densities and thus lower weight of the manufactured components, controlled processability, controls hydrophobic / hydrophilic behavior, reduction of water cement value, rheoplastic flow behavior, easier processing, - high storage stability, lower costs, with only a slight influence on the technical properties.

The PU powders can be used in amounts of 0.1 to 25% by weight, preferably 1 to 15% by weight, particularly preferably 1 to 5% by weight, based on the solids content of the building material mixture.

The powders according to the invention were incorporated into types of concrete such as lightweight concrete, prestressed concrete, structural concrete, exposed concrete, pumped concrete, etc. in the context of orientation tests. For this purpose, 1 and 2 wt .-% powder was used in the concrete. A strong rheoplastification of the concrete types is observed. Furthermore, essential properties such as cube compressive strength, core pressure resistance, modulus of elasticity, creep value, shrinkage value etc. are not adversely affected. The dependency of the strengths on the amount of mixed water is the same as for standard concrete.

Rheoplastic concrete produced in this way does not separate and shows no blouting. It has a lower permeability.

Claims

1. Process for the separation of asymmetrical plastic-non-metal composites, preferably coated, foamed composite components, consisting of a solid, non-compressible non-metal layer and optionally a number of stretchable, optionally foamed plastic layers, to obtain a plastic powder, characterized that the separation process is carried out in a roller mill, in which the rollers are arranged parallel to the axis, rotate in opposite directions and at different speeds, in which a roller gap is set, the width of which corresponds to the thickness of the non-metal layer and in which the

Non-metal layer rests on the slower rotating roller and the ratio of the peripheral speeds of the two rollers is chosen to be greater than one plus the quotient of the elongation at break of the plastic material in% and the number 100.

2. The method according to claim 1, characterized in that the ratio of the peripheral speeds of the two rollers exceeds a value of 1.5 to 2.0, based on one plus the quotient of the elongation at break of the plastic material in% and the number 100.

3. The method according to claim 1 or 2, characterized in that the ratio of the peripheral speeds of the two rollers takes a value in the range of above 2, preferably above 4, based on one plus the quotient of the elongation at break of the plastic material in% and the number 100 .

4. Process according to claims 1 to 3, characterized in that the composite separation is carried out on a roller mill with smooth rollers.

5. The method according to claims 1 to 3, characterized in that the verbimd separation is carried out on a roller mill, in which the faster rotating roller has a surface structure, preferably an axial corrugation or an etching.

Process according to claims 1 to 5, characterized in that the composite separation is carried out on a roller mill in which at least the faster rotating roller has a temperature in the range from 30 ° C to 200 ° C, preferably 50 ° C to 150 ° C and particularly preferably in the range of 60 ° C to 100 ° C.

Use of polyurethane powders with particle sizes less than 0.5 mm in diameter to modify inorganic building materials.