RU2813505C1 - Method for obtaining dispersed recyclate from quartz composite - Google Patents

Abstract

FIELD: construction materials.

SUBSTANCE: production of moulded products from a quartz composite, consisting of a polymer matrix, for example, based on acrylate, with filler particles used in the production of kitchen sinks, shelves, sanitary products: shower trays or shower bases, as well as floor or wall panels. Dispersed recyclate from a quartz composite is obtained by grinding moulded products from a quartz composite consisting of a polymer matrix and particles of inorganic quartz-containing filler in an amount of more than 60 wt.%. Pre-crushed pieces of moulded products are ground in a hammer mill to obtain particles that form a recyclate of the target fraction of 0.1-1 mm.

EFFECT: possibility of processing moulded products from a quartz composite to obtain the target fraction in one grinding stage for further use in foundry mass for the manufacture of new products.

20 cl, 6 dwg, 1 tbl

Description

The invention relates to a method for producing dispersed recyclate from a quartz composite by grinding molded products from a quartz composite consisting of a polymer matrix and inorganic filler particles introduced into it.

Quartz composite products are known in various forms. For example, kitchen sinks, shelves, sanitary products such as shower trays or shower trays, as well as floor or wall panels, baseboards, etc. are made from quartz composite. These molded articles consist primarily of a polymer matrix, such as an acrylate-based one, with filler particles embedded in a cured polymer matrix. These may be particles of inorganic or organic filler. For example, quartz sand is used as such a filler. Often, colored pigments are also introduced into the polymer matrix to impart a specific color to the molded product.

Over time, there is inevitably an accumulation of used molded products that are no longer required, either because they are replaced after a long period of time as part of renovation or refurbishment measures, or because they are defective, or for other reasons. Of course, when producing new molded parts, there is also a corresponding defect that is not suitable for sale. With the increasing use of such quartz composite molded products, the number of old products that are no longer in use is also inevitably increasing. They are usually disposed of by waste disposal companies.

Thus, the basis of the invention is to develop a method allowing further processing of such molded products from quartz composite.

To solve this problem, a method is proposed for producing dispersed recyclate from a quartz composite by grinding molded products from a quartz composite, according to which pre-crushed pieces of molded products are ground in a hammer mill to obtain particles forming the recyclate.

In the method according to the invention, pre-crushed pieces of molded articles are ground in a hammer mill, during this grinding process a sufficient number of particles are formed, the size of which is in the target size range that the dispersed recyclate should have. In such a hammer mill, the material to be crushed is crushed by kinetic impact grinding. Attached to the rotor are a large number of movable hammers, which rotate above the rotor in the mill body. Hammers strike the material being crushed, that is, pieces of molded products, which leads to their crushing. In addition, the crushed pieces are also thrown towards the walls of the case, breaking down even more. During the stay of the crushed material in the housing, the crushed material is continuously subjected to impacts due to the relatively high speed of rotation of the rotor and, consequently, the hammers, and is further crushed. In this case, corresponding small particles are formed, a significant part of which have sizes that are in the range of the desired target size, or smaller sizes (fine fraction).

Surprisingly, it was found that the material being ground, i.e. pieces of molded products are sufficiently crushed in such a hammer mill at room temperature, while, on the one hand, a sufficiently large proportion of particles forming the recyclate, having the desired granulometric composition, is formed in just one grinding operation, on the other hand, a particular advantage is the absence of clumping or briquetting, i.e. the formation of large particles that cannot be used as a recyclate, in particular, as a recyclate to be added to the foundry mass for the production of new products. In other mills, such as the roller mill, comminution occurs by shearing the material being ground, which means introducing a high level of shear energy. This shear energy presumably leads to heating of the crushed particles, which in turn leads to softening of the polymer matrix, at least in the surface zone. Therefore, individual particles become slightly sticky, which may cause clumping or briquetting. Now, unexpectedly, it turned out that such processes do not occur in a hammer mill, since there the material is not subjected to shear stresses, but only impact energy or impact-reflective energy is supplied when thrown against the wall of the housing. This energy or energy input does not cause excessive heating of the particles, so that surprisingly there is no surface stickiness and therefore no clumping or briquetting occurs. Thus, the material to be ground can be successfully ground in such a hammer mill for a longer period of time, which in turn results in a sufficiently large proportion of particles that are within the target size range during the grinding process.

Thus, the method proposed by the invention for the first time makes it possible to obtain a sufficiently large number of particles forming the recyclate, and on the other hand ensures its economically viable production. Therefore, the method according to the invention allows for the expedient recycling of corresponding old quartz composite products to form a dispersed recyclate, which can be reused as an additive, for example as a casting additive for the production of new quartz composite products.

In an improved embodiment of the invention, provision can be made for separating the particle fraction containing recyclate-forming particles with the maximum target size using a sieve. According to this first embodiment of the invention, only the particle fraction that contains particles smaller than or equal to the target size, including any very fine particles, is screened from the hammer mill. If, for example, the target particle size is 1.0 mm, then particles whose size is a maximum of 1.0 mm or less are selected as the specified particle fraction. Larger particles remain in the hammer mill and can be processed further until they are reduced to the required degree and removed. Thus, here there is a direct selection, preferably continuous, of only the target fraction.

In this case, the target size can be 1.0 mm, in particular 0.8 mm. This target size is appropriate when the dispersed recyclate is to be used as an additive to the foundry mass for the production of new molded products from a quartz composite. This target size corresponds to the maximum size of inorganic or organic filler present in the foundry mass and therefore in the new product. The individual recyclate particles are partially composed of a polymer matrix and contain particles of inorganic or organic filler that were present in the old recycled product. Now, through the recyclate particles, a certain proportion of “old fillers” can be added to the foundry mass as a filler, while the choice of the target size of the recyclate particles ensures that the filler particles introduced through them always have the maximum filler grain size that should be present in the new molded product .

In contrast, in an alternative embodiment of the method to that described above, in which the target fraction is taken directly from the hammer mill, it is provided that a first fraction of particles with a maximum particle size that is larger than the target particle size forming the recyclate is taken from the hammer mill through a sieve, after which in the next sieving device, from the first fraction of particles, a second fraction of particles containing particles forming the recyclate with a size smaller than or equal to the target size is selected and separated from a third fraction of particles containing particles whose size is larger than the target size. Thus, in this embodiment of the method, a first fraction of particles that is larger than the target fraction itself is screened from the hammer mill and then screened in a screening device to separate the desired target fraction (ie, the second particle fraction). Consequently, the screening device classifies the recyclate particles of the first coarse particle fraction taken from the hammer mill. Through the sieve of the hammer mill, through which the first fraction of particles is separated, it is possible not only to set the maximum size of the first fraction of particles, but also to vary the residence time of the crushed material in the mill. The larger the sieve, i.e. holes in the sieve and, thus, the larger the maximum size, the shorter the residence time of the crushed material in the hammer mill, and the smaller the sieve, respectively, the maximum size, the longer the residence time of the crushed material in the hammer mill, since more grinding is required to pass through sieve. This also means that the fraction of fines, that is, the fraction of very small particles that are also significantly smaller than the target size of the target fraction, varies depending on the size of the sieve used. With a larger sieve and therefore a shorter residence time the proportion of fine particles is smaller, and with a smaller sieve and a longer residence time it is higher.

Thus, according to this variant of the method, two separate fractions are collected in the sieving device, namely a second fraction of particles, which contains particles forming the recyclate, the size of which is less than or equal to the target size, and a third fraction of particles, which contains particles of a size larger than the target size. In this case, the second fraction of particles can be used as the final target fraction, or it can also be further classified, which will be discussed later. The third fraction of particles can also be used further if desired, which will also be discussed in more detail below.

In one improved embodiment of the invention, the maximum particle size of the first particle fraction can be 5 mm, in particular 4 mm. This means that the hammer mill sieve has a mesh size of 5 mm, in particular 4 mm, whereby for classification it is preferable to use a wire mesh sieve, which provides a sufficiently large working surface to reduce the residence time of the particles in the hammer mill. Although in principle a maximum particle size of <4 mm is possible, the proportion of fine particles, that is, the proportion of particles significantly smaller than the target size, increases significantly.

Here too the target size should be 1.0 mm, in particular 0.8 mm. This is true in particular when the recyclate particles are to be added as an additive to the quartz composite casting mass for the production of new molded products. Again, in this embodiment of the method, the target size essentially corresponds to the maximum size of inorganic or organic fillers present in the new molded article.

As indicated, in this second embodiment of the process of the invention, a third particle fraction is obtained containing particles whose size exceeds the maximum target particle size of the second fraction. It is preferable to return this third fraction of particles to the hammer mill for further grinding. This means that these still too large particles are processed again in the hammer mill and crushed until they reach a size that is in the target size range or less, so that in the next screening step in the sieve device they end up in the second fraction particles. Thus, a third fraction of particles is returned to the process, which can also occur several times, so that, based on a given amount of filler in the pieces of molded products, a yield of dispersed recyclate of almost 100% can be achieved.

As described above, the crushed particles of the first particle fraction are fed from the hammer mill to the screening device, respectively, the particles of the third particle fraction from the screening device are returned to the hammer mill again. This movement can be carried out manually, that is, the operator manually transports the material from the hammer mill to the screening device or, respectively, from the screening device to the hammer mill and leaves it there.

However, it is preferable for automatic transport to take place via a suitable transport device. Thus, such a transport device for moving the first particle fraction may be, for example, a belt conveyor, for example a Z-shaped conveyor, which carries the first particle fraction from the hammer mill to the screening device. The use of a Z-shaped conveyor is advisable, since in a hammer mill the first fraction of particles is preferentially discharged downwards and fed to the screening device from above, while the corresponding second and third fractions of particles, in turn, are preferentially discharged from below.

To transport the third fraction of particles from the screening device back to the hammer mill, it is also possible to provide a belt conveyor, for example a vibrating chute or the like.

If, for example, the third fraction of particles is transported manually, then the third fraction can be collected, for example, in a collection container of an appropriate size, for example, in a soft big bag container, and then the filled collection container can be transported using an appropriate transport means, for example, a loader or the like, to a hammer mill, for example to a conveyor belt starting at the floor, along which the supplied crushed material moves upward to the loading device of the hammer mill.

The operating mode of both the hammer mill and the screening device can, in principle, be continuous, that is, pre-crushed pieces of molded products and, if provided, particles of the third fraction of particles are continuously fed into the hammer mill, and the particles are continuously selected and also continuously fed to the screening device , where they are continuously separated into appropriate fractions. Thus, such a continuous process can be carried out with very high productivity. As an alternative to this, it is of course possible to envisage an intermittent process, during which only a certain amount of crushed material is processed without a continuous additional supply of new crushed material. This is only realized when the introduced crushed material is completely processed.

As has been described, in the sieving device, a second particle fraction is separated from the first fraction of particles through a sieve, the sieve being a mesh sieve or the like. This second particle fraction contains particles whose maximum fineness corresponds to the target size, but the size can also be smaller and significantly smaller, that is, the second particle fraction also contains a correspondingly high proportion of fines, that is, very fine particles of a very small size. If the target size is, for example, 1.0 mm or 0.8 mm, then the second fraction also contains particles of only 0.2 mm, 0.1 mm or even smaller, down to powdery particles, which ultimately no longer are considered granulate. In principle, the second fraction of particles, i.e. the target fraction may also contain a fine fraction, for example, as an additive to the casting mass. However, if a fine fraction is not desired, an advantageous improved embodiment of the invention provides, in the screening device or additional screening device, for the formation and selection from the second fraction of particles using a sieve of the fourth fraction of particles with a maximum size that is less than the target size, so that remains and is selected a fifth particle fraction containing recyclate-forming particles. Thus, in the screening device at the second screening level, further classification of the second particle fraction is carried out. It is separated into a fourth particle fraction, which contains the unwanted fine particles to be removed, and a fifth particle fraction, which then corresponds to the final target fraction. In this case, the maximum size of the fourth particle fraction, that is, the fine fraction, is determined by an additional sieve, for example a mesh screen, so that this fourth fraction contains only particles of this size, or even smaller ones. Thus, the final fifth fraction of particles, i.e. the target fraction contains only recyclate particles whose size is in the range between the target size and the maximum particle size of this second screening level. As a result, the target fraction contains no or only a small proportion of fine particles, which can be beneficial in relation to the rheological properties of the casting mass to which the recyclate particles are added. If both levels of screening are implemented in a common screening device, then corresponding sequential screening stages are provided. If two separate sieving devices are used, they can, for example, be connected by means of a transport device, with which the second particle fraction is automatically transported to the second sieving device.

The maximum size of the fourth particle fraction should be 0.1 mm, in particular 0.2 mm. The larger this maximum size, the smaller the size range of the final recyclate particles.

According to the invention, for sifting the first fraction of particles and/or for sifting the second fraction of particles, mesh sieves are used having a given mesh size, which ensures appropriate separation and classification of the fractions.

It is particularly preferable to use as starting material for the method according to the invention pieces of molded articles which contain inorganic and/or organic filler particles incorporated into the polymer matrix in an amount of ≥ 60 weight percent (wt.%), in particular ≥ 65 wt.%. Thus, the molded product pieces must contain inorganic and/or organic filler particles in a minimum proportion of at least 60 wt.%, and preferably higher. This means that the proportion of the polymer matrix should not be too large, since the goal is to recover the fillers, in particular through the recyclate, i.e. adding recycled fillers to foundry stock to produce new molded products.

In addition to crushing composite materials of different colors, the described method can also be successfully used to crush pieces of molded products of substantially the same color in a hammer mill. As a result, the dispersed recyclate of the target fraction may ultimately have a uniform color. As discussed, molded products, including recycled molded products, typically contain colored pigments to give them their individual color. These color pigments are usually added to the foundry mass as a pigment paste as part of the new manufacturing process. Since new products must also have a specific color, and since the dispersed recyclate also inevitably contains colored pigments, it is necessary to ensure that the dispersed recyclate does not change the target color of the new molded product, which is determined by the pigment paste. Therefore, according to the invention, it is preferable to grind together only the same type, i.e. single-color pieces of molded products so that the recyclate particles have a uniform color. Of course, the molding pieces do not have to be completely identical in color; on the contrary, it is also possible to process molding pieces slightly different in color together, for example, anthracite gray moldings together with black moldings, etc., whereby Naturally, the final mixed color is ultimately determined by the ratio of the number of molded products of different colors.

The pre-shredded, typically irregularly shaped molded pieces should preferably have a maximum length of about 40 cm, in particular about 30 cm. The molded pieces are obtained either by manual crushing of the processed molded pieces or by a suitable pre-shredding process, e.g. using a roller in a container or the like, where the molded products are respectively crushed by a heavy roller.

The molded product pieces themselves can be fed into the hammer mill manually or automatically using a conveying device such as a conveyor belt.

Various quartz composite moldings can be used as the molded products to be processed. It is preferable to process molded articles that correspond to the articles that will be subsequently produced, since the material composition of the old molded articles is substantially the same as the composition of the new molded articles being manufactured. Thus, if kitchen sinks are produced as new molded products, then according to the invention, kitchen sinks must also be used as old molded products within the framework of the process according to the invention. If such kitchen sinks are made of casting mass of different composition, i.e. Kitchen sinks consist of different composite materials; it is also permissible to use only old kitchen sinks in which the composition of the material matches the composition of the new kitchen sinks being produced to obtain recyclate added to the foundry mass. However, this additional specification is not strictly required.

In addition to the method itself, the invention also relates to the dispersed recyclate obtained by the method described above.

In addition, the invention relates to the use of the above-described dispersed recyclate as an additive to the casting mass for the production of a molded product from a quartz composite, in particular a kitchen sink.

Finally, the invention relates to a quartz composite molded product, in particular a kitchen sink, produced using the above-described dispersed recyclate.

Other advantages, features and details of the invention will appear from the embodiments described below, as well as from the drawings. On the drawings:

fig. 1: schematic diagram of a device for producing dispersed recyclate from a quartz composite using the method according to the invention fig. 2: flow diagram explaining the method according to the invention fig. 3: graph showing particle size distribution for three different grinding materials fig. 4: graph showing the effect of particle size on product yield through a sieve or outlet fig. 5: a graph showing the particle size distribution for different sequential grinding operations, and fig. 6: graph showing particle size distribution for sequentially crushed materials, each taken from a previous grinding operation

In fig. Figure 1 shows device 1 for producing dispersed recyclate from a quartz composite. The device 1, which is shown purely schematically, includes a first conveying device 2, for example a belt conveyor, and pre-crushed pieces of molded articles 3 are supplied to this conveying device 2. These pre-crushed molding pieces 3 are crushed fragments of a quartz composite molding and, like this molding, consist of a polymer matrix embedded with inorganic and/or organic filler particles and usually also colored pigments. The molded products shredded to form molded pieces 3 are, for example, kitchen sinks that are no longer used or are unusable.

Through the first transport device 1, the pieces 3 of the molded products are fed into the hammer mill 4, where they are crushed by a rotating hammer or impact tool. In this case, the pieces of 3 molded products are broken by rotating hammers, that is, the grinding process occurs due to the introduction of impact energy in combination with the fact that the crushed pieces, due to the relatively high speed of rotation of the rotor and, accordingly, the hammers, amounting to several tens of meters per second, hit against the walls of the mill, where they are also crushed.

A sieve, not shown in detail, is built into the hammer mill, with which it is possible to separate the first fraction of particles with a maximum particle size exceeding the target particle size of the particles forming the recyclate. That is, through this sieve, for example a wire mesh sieve, pass particles whose size corresponds to the maximum size specified by the sieve, or less than this maximum size. Particles that do not pass through the sieve remain in the hammer mill and are further impacted and are therefore crushed until they can pass through the sieve.

The first fraction of particles is then conveyed on a second conveying device 5, in the example shown a Z-shaped conveyor with a corresponding conveyor belt, to the screening device 6 and fed to the screening device 6. There, the first fraction of particles is screened at at least one screening level to form a second fraction a particle fraction that contains recyclate-forming particles. These second fraction particles have a size that is less than or equal to the target size. In addition, a third particle fraction is formed, which contains particles larger than the target size. Thus, in the screening device 6, a relatively coarse first particle fraction is classified to form, on the one hand, a volume of particles containing particles whose size is ultimately in the target size range or less, and to form a third particle fraction containing particles , which are larger than this number of target size particles.

The second fraction of particles in the illustrated embodiment is introduced from the screening device 6 into a receiving container 7 provided for disposal, for example, on the shown loader, and accumulates there until a certain filling level is reached, after which this second fraction of particles is finally withdrawn and fed to further use, for example, as an additive to foundry mass for the manufacture of new kitchen sinks.

A third fraction of particles is also collected in a suitable collection vessel 8. Since this third fraction of particles consists of particles outside the target size range, i.e. their size is still too large, they are sent to the first conveying device 2, as shown by the dotted line 9 indicating the transport path, and again fed to the hammer mill 4 for re-grinding. Thus, a too large third fraction of particles is returned. As a result of the new grinding, a sufficiently large proportion of the particles are further reduced so that these particles are in the target size range and subsequently fall into the second fraction of particles. This return of the third particle fraction to the first transport device 2 can be carried out manually, for example by towing a forklift shown here, with which the container 8 can be moved. Alternatively, instead of the receiving container 8, an additional transport device, for example a vibrating chute or a conveyor, can be provided a belt onto which particles of the third fraction fall or are fed so that they automatically return to the first transport device 2.

Of course, instead of the shown receiving container 7, the second fraction of particles, i.e. the target fraction may also be placed on a conveyor transport device, such as a conveyor belt, on which it is transported, for example, to a remote packaging station or the like.

As described above, in the illustrated embodiment, the screening device 6 has only one screening level, through which the first particle fraction is separated into the second and third particle fractions. As indicated, the second fraction of particles contains particles whose size does not exceed the target size, but, of course, can be smaller, down to a small fraction with a minimum size, that is, with a particle size of less than 0.2 or 0.1 mm. This fine fraction may remain in the second particle fraction if it does not interfere with subsequent processing. However, if necessary, it can also be removed. For this purpose, the screening device has a second screening level in which the second particle fraction is screened again to form a fourth particle fraction containing only fines and a fifth particle fraction, which is then the final target fraction. This additional level of screening, which, like the first level of screening, is implemented by means of a mesh screen or the like, sets a maximum particle size that is less than the target size. Thus, the fourth fraction of particles, i.e. fine fraction, contains only particles that have this maximum size or less, i.e. all the little things down to the powder. In contrast, the fifth particle fraction contains only particles whose size is less than or equal to the target size and larger than this maximum size at the second screening level. Then the fourth and fifth fractions of particles are respectively withdrawn. While the fifth fraction of particles, that is, the target fraction, is sent for further processing, the fourth fraction of particles, that is, the fines fraction, can be discarded. Thus, in the device shown in FIG. 1, instead of one receiving container 7, two such containers are provided. The fourth fraction of particles falls into one receiving container, i.e. fine and very fine fractions, and the last fifth fraction of particles ends up in another receiving container.

The maximum particle size of the first fraction, determined by the sieve of the hammer mill 4, is, for example, 5 mm, in particular 4 mm. The gap width of the sieve should not be smaller, otherwise the fine fraction will be too coarse during the grinding process.

The target size specified by the first screening level of the screening device 6 should be approximately 1.0 mm, preferably approximately 0.8 mm.

The maximum particle size that defines fines should be about 0.1 mm, preferably about 0.2 mm. This means that the size of the particles that make up the final fourth fraction of particles, i.e. the target fraction ultimately ranges from ≤ 1.0 mm to > 0.1 mm, preferably from ≤ 0.8 mm to > 0.2 mm.

In fig. 2 is a flow diagram illustrating the basics of the individual process steps as well as the resulting particle fractions.

In step S1, the material to be crushed, that is, the pre-crushed pieces of molded products 3, is fed to the first conveying device 2 and conducted into the hammer mill 4.

In step S2, the supplied grinding material is ground in the hammer mill 2. As a result of this grinding, the first particle fraction PF1 is formed.

Then said first fraction PF1 of particles is taken from the hammer mill in step S3 through the sieve of the hammer mill 4 and is carried through the second transport device 5 to the sieving device 6 and introduced into it.

In step S4, the first particle fraction PF1 is screened in the sieving device 6, whereby a second particle fraction PF2 and a third particle fraction PF3 are formed. For this purpose, the screening device 6 has a first sieve forming a first screening level, for example a mesh sieve or the like, which defines the target coarseness. It is, for example, 1.0 mm, or 0.9 mm, or 0.8 mm, depending on what the maximum target size of the final recyclate should be. Thus, the second fraction PF2 of particles contains particles with a size less than or equal to the target size, for example, 1.0 mm or 0.8 mm.

In contrast, the third fraction of PF3 particles contains only particles larger than the target size, that is, larger than 1.0 mm or 0.8 mm. This third fraction of PF3 particles is then automatically sent back in step S5, for example via a transport device, to the first transport device 2, so that it is again fed in step S1 to the hammer mill 4, where these still rather large particles are crushed again and returned to the cycle grinding and sifting.

The second fraction of PF2 particles contains, as already mentioned, particles whose size is less than or, at most, equal to the target size. Thus, it also includes an appropriate proportion of fine particles, i.e. much smaller particles. To separate this fine fraction, the second particle fraction PF2 is screened, as represented by step S6, using the screening device 6 at the second screening level using a second sieve, for example, a mesh screen or the like, to form a fourth particle fraction PF4 and a fifth particle fraction PF5 . The mesh size of the sieve at this second screening level determines, in turn, the maximum particle size, for example, 0.1 mm or 0.2 mm, which ensures screening out unwanted fines. Thus, the fourth fraction of PF4 particles contains only very small particles, which form the fine fraction.

In contrast, the fifth fraction of PF5 particles contains only particles whose size is in the desired size range, which is limited above by the target size, that is, the preferred particle size, and below by the maximum size at which the fine fraction begins. Thus, the fifth fraction of PF5 particles contains, for example, only particles ranging in size from >0.2 mm to ≤0.8 mm.

In step S7, a fourth fraction of particles is selected, which can, for example, be discarded if the fine fraction cannot be reused in any other way. On the other hand, the final fifth fraction of PF5 particles, which can be further processed as recyclate, is then collected in step S6, for example after it has been collected in a receiving container, or using a conveying device or the like.

As part of the research, various quartz composite materials were ground in a hammer mill and the grinding result was determined.

In the first experiment, the grinding characteristics of three different quartz composite compositions were investigated. The starting material was three quartz composite kitchen sinks manufactured by the present Applicant, which consisted of different quartz composites.

One sink was made from a material manufactured by the Applicant known as Cristalite®, a second sink was made from a material manufactured by the Applicant known as Cristadur®, and a third sink was made from a material manufactured by the Applicant known as Cristadur® Green Line.

In addition to the MMA-based polymer binder forming a polymer matrix and color pigments, the Cristadur® sink also contained an inorganic filler in the form of quartz sand in an amount of 68-75 wt.%.

The sink made of Cristalite® material, in addition to the polymer binder matrix and color pigments, also contained an inorganic filler in the form of quartz sand in an amount of 70-75 wt.%.

The sinks were used to form pieces of molded products, i.e. The sinks were pre-shredded, and the length of the crushed pieces did not exceed 30 cm. In order to be able to process a sufficient amount of crushed material, several identical sinks of each type were crushed.

A Gebr hammer mill was used to crush the crushed material. Jehmlich GmbH, type HM 672, operating on the impact-reflective principle. Rotating hammers strike the material to be crushed in the grinding chamber. Upon reaching the required grinding fineness, the crushed material leaves the grinding chamber through a sieve with a bar grid. The wire mesh screen had a gap of 4 mm, which limits the proportion of larger particles passing through the screen.

This hammer mill was used to grind each grinding material for different types of material. Grinding continued until all available material to be crushed was ground.

Particle size distribution results for three different grinding materials are presented in Fig. 3.

The abscissa axis indicates the particle size in mm, and the ordinate axis indicates the corresponding proportion in weight percent.

Curve labeled I shows the particle size distribution for Cristalite®, curve II for Cristadur®, and curve III for Cristadur® Greenline.

It turned out that the resulting crushed material for all studied compositions has a comparable granulometric distribution. There is a first peak in the range of approximately 3.0-1.0 mm, and a second peak occurs in the range of 0.3-0.06 mm.

Clumping or briquetting of the relevant material in the hammer mill did not occur with any of the materials tested, meaning that all feed crushed material could be crushed and screened.

For the production of new molded products, i.e. new kitchen sinks made from Cristalite® or Cristadur® materials, inorganic fillers were preferably used, i.e. mainly quartz sand with a maximum particle size of about 0.8 mm. Therefore, as shown above, from the resulting crushed material, an appropriate particle fraction with a size of ≤ 0.8 mm is suitable.

The yield of crushed material from the grinding tests shown in the graph above with a particle size ≤ 0.8 mm is given in the table below.

material Cristalite® Cristadur® Cristadur® Greenline approximate yield (%) 60 48 45

Thus, each material can already be crushed in the first grinding operation to such an extent that it already contains a sufficiently high proportion of particles having a certain target size or a smaller size.

In the following experiment, we studied, in particular, the influence of the outlet on the residence time of the material in the mill and the resulting granulometric distribution of the ground material. The experiments were carried out on a hammer mill HA800 from Erdwich Zerkleinsystems GmbH with an adjustable outlet gap for product discharge, rather than with a mesh screen. The width of the outlet gap was 3 mm. Due to the fact that there was only one outlet gap with a smaller opening width to release the product, the residence time of the material in the mill increased significantly. The results are shown in Fig. 4.

The abscissa axis again shows the particle size in mm, i.e. size, and the corresponding weight percentage of crushed material is again shown on the y-axis. Curve I shows the particle size profile for a 4 mm mesh screen, and curve II shows the particle size profile for a 3 mm outlet opening.

It can be seen that when using a 4 mm mesh screen in the Jehmlich hammer mill HM 672, the proportion of particles between 4.0 and 0.5 mm is significantly higher than curve II for the Erdwich hammer mill HM800 with 3 mm outlet. These ratios are reversed from a particle size of about 0.5 mm, which means that the proportion of fines with the inevitably longer grinding time in the case of a single 3 mm outlet is significantly greater than in grinding using a mesh screen, where much material is removed earlier and thus the residence time is significantly shorter.

If we also take into account the fraction of particles with a size of ≤0.8 mm, then when grinding with one outlet gap and, as a result, with a longer residence time of the material in the hammer mill, there is an increase in the yield of particles with sizes in the target range, according to the above graph up to 90%. However, this is also accompanied by a significant increase in the proportion of fine material, with fine material being, for example, particles ≤0.2 mm in size. If too high a fines content is not desired, the sieve size should not be too small.

As already described in connection with figures 1 and 2, the first fraction of particles taken from the hammer mill 4 is screened in the screening device 6. The second and third target fractions are formed, the third target fraction containing, as described, particles larger than the target fineness recyclate particles. This third fraction of particles can be returned to the hammer mill 4 for re-grinding.

The following experiment examined the effectiveness of the second grinding operation in terms of the yield of suitable ground material, that is, the ground material was first ground in a hammer mill and then the first fraction of particles was classified in a screening device, after which the third fraction of particles was returned to the hammer mill and ground a second time and then again classified in the sieving device. In this case, a quartz composite material of the Cristalite® type was studied.

The results are shown in Fig. 5. Here again, the particle size distribution in mm is plotted along the abscissa axis, and the corresponding percentage is plotted along the ordinate.

Curve I shows the particle size distribution or particle size distribution after the first grinding operation, curve II the particle size distribution or particle size distribution after the second grinding operation, and curve III the distribution after both grinding operations.

The first grinding stage produces a particle size distribution in which a significant portion of the particles are already in the target size range, i.e. ≤0.8 mm.

At the second stage of grinding, the volume of particles obtained in the first stage of grinding, the size of which is >0.8 mm, is again ground in a hammer mill, that is, the over-grid product from the first stage of grinding is fed again. As can be seen from curve II, this grinding step also produces a fraction of particles with dimensions <0.8 mm, as well as a fraction of particles still containing larger particles. However, the degree of comminution in this second grinding operation is less than that in the first grinding operation.

However, it turned out that thanks to the return of the over-lattice product, that is, the third fraction, in accordance with the description of the previous figure, a new yield of particles in the target size range is achieved.

This is also evident from curve III, which shows the effective particle size distribution after two grinding cycles. The vast majority of the crushed material obtained after the two grinding operations is already in the desired size range of ≤ 0.8 mm, and mostly in the desired grain size range of 0.8-0.2 mm. This means that by repeatedly reusing the over-grid product, i.e. third particle fraction, a continuous increase in yield up to almost 100% can be achieved.

In addition to experiments using a hammer mill according to the invention, another process for grinding quartz composite moldings was also investigated. Here, multi-stage grinding was implemented using a roller crusher and a roller mill. Grinding was carried out in four stages.

In the first crushing stage, pre-crushed pieces of molded products with a maximum length of 30 cm were crushed using a jaw crusher type BB 400/250 from Merz Auffertigungstechnik GmbH, the crusher gap was 20 mm.

In the second grinding stage, the material to be crushed, taken from the first grinding stage through the crusher gap, was crushed in a roll crusher with a pyramidal cam profile type WBG 5/4 from Merz Auffertigungstechnik GmbH; The crusher gap here was 1.0 mm.

The crushed material from the second grinding stage, which has passed through the gap of the crusher, i.e. the fine fraction from the second grinding stage was then further ground in a WBP 6/4 roller mill from Merz Auffertigungstechnik GmbH, the gap was set at 1.5 mm.

Then, in the fourth grinding stage, the crushed material that passed through the gap in the third grinding stage, i.e. the small fragments obtained there were then crushed again in a roller mill, but in this case the crusher gap was set at 0.5 mm.

The results of individual grindings were classified by particle size, the results are shown in Fig. 6.

Curve I shows the particle size distribution of the crushed material obtained in the first grinding stage. Curve II shows the particle size distribution of the crushed material obtained in the second grinding stage. Curve III shows the particle size distribution of the crushed material obtained in the third grinding stage. Curve IV shows the particle size distribution of the crushed material obtained in the fourth grinding stage.

At the first stage of grinding, the pieces of molded products, due to the large gap of the crusher, are crushed only coarsely; it is clear that practically no particle fraction is formed here, which is in the target size range, i.e. preferably ≤0.8 mm. The yield of recyclate particles of the target size here is only about 0.3% of the total amount of introduced material.

At the second grinding stage, only the part obtained at the first grinding stage and passing through the gap of the crusher is crushed. It can be seen that further grinding is possible at the second stage, but even here there is only a very small proportion of particles whose size is in the target range of ≤0.8 mm. The yield of particles ≤0.8 mm in size was about 5.9%.

Then the fraction of the crushed material, which passed through the gap of the crusher at the second grinding stage, was crushed at the third grinding stage in a roller mill with a gap width of 1.5 mm. The result is shown by curve III.

There is also a high peak here in the coarseness range of approximately 2.5-8 mm, almost all of the material is in this range. In contrast, only a small fraction of particles were obtained here, which are in the target size range of ≤0.8 mm.

Then, at the fourth grinding stage, the fraction of particles that passed through the crusher gap at the third grinding stage was again crushed in a roller mill, but with a smaller crusher gap of 0.5 mm. The result of grinding is shown by curve IV. Here there is a wider size distribution in the ≤2.5 mm range, indicating that further refinement has taken place. The proportion of particles in the target size range ≤0.8 mm also increases. However, the yield of material within the target size range is only about 46%. In addition, it was found that the proportion of coarser material increased slightly compared to the third grinding stage. This is due to the briquetting that takes place during this comminution process involving shear stress. The sticky briquetted material has a higher particle size than the original material from the third grinding stage.

Thus, at the end of the four-stage grinding process, only a portion of the original feed material can be used, since the amount of grind material processed in the individual grinding stages was continuously reduced, since only the portion that passed through the corresponding sieve or gap was subjected to further processing. In order to obtain a ground material that leads to a more or less acceptable yield, in this case it was necessary to first carry out three grinding processes. The material fed to this fourth grinding stage already had a strikingly small maximum particle size, a consequence of the third grinding stage having a crusher gap of 1.5 mm. Even when grinding this already very highly ground material (as already mentioned, the starting material was pieces of molded products about 30 cm long, fed to the first grinding stage), a yield of only about 46% is achieved, i.e. More than half of the resulting crushed material does not meet the target size range.

In addition, on the one hand, already at the third, and on the other hand, also at the fourth stage of grinding, clumping or briquetting of the crushed material was observed, i.e. composite granulate, which ultimately leads to a significant deterioration in the yield of material with the target particle size range. This clumping or briquetting occurs, as already explained, as a result of the sticking together of the material subjected to shear stress in the roller mill, which leads to strong heating and softening of the polymer matrix, i.e. resin binder, and, consequently, to the adhesion of particles.

On the contrary, the method according to the invention makes it possible to obtain, in a single grinding step, from large, pre-crushed pieces of molded articles, preferably with a length of maximum 30 cm, a fairly large proportion of the target particles, i.e. a fraction with a particle size of, for example, ≤1.0 mm or ≤0.8 mm, depending on how the maximum target size is determined. In addition, the method according to the invention is advantageous in that briquetting does not occur, i.e. clumping, i.e. material whose particle sizes do not correspond to the target size range can be ground again without problems. It is also possible to carry out a continuous, longer grinding process, since the impact load on the material being ground does not result in high energy consumption, unlike the shear stress used, for example, in mills of the type described above during the grinding process.

Thus, with the method according to the invention using a hammer mill, it is possible to carry out efficient and cost-effective production of dispersed recyclate from a quartz composite.

The production of the recyclate, which, as already stated, preferably has a maximum fineness that corresponds to the maximum fineness of the inorganic or organic filler, for example quartz sand, used in the primary manufacture of the molded product, in particular a kitchen sink, is very simple. It is only necessary to pre-treat the recyclate particles before introducing them into the casting mass. As described above, the recyclate particles also contain a certain proportion of a polymer binder matrix, that is, an acrylic matrix, which, if untreated recyclate particles are introduced into the casting mass, swells somewhat in the monomeric acrylate contained therein, which leads to an increase in the viscosity of the casting mass. To avoid changing the rheological properties of the casting mass or intermediate product, for example pigment paste, to which the recyclate may be added, the recyclate particles must only be pre-swollen with a suitable amount of monomeric acrylate. Therefore, an appropriate amount of monomeric acrylate is added to the recyclate granules to allow the particles to swell, swelling usually being completed within 24 hours at the latest. The progress of swelling can be monitored rheologically.

The recyclate particles pre-treated in this way are then added to the foundry mass either directly as an independent intermediate product or added, for example, to a pigment paste, which is then introduced into the foundry mass. The casting mass can then be processed like a regular casting mass to produce a shaped casting, but it contains a significant proportion of recycled materials, i.e. reusable fillers.

Although in the example in the sieving device 6, both the first particle fraction is divided into fractions PF2 and PF3, and the second particle fraction PF2 is also divided into fractions PF4 and PF5, i.e. There are two stages of sifting; to separate the PF2 fraction into fractions PF4 and PF5, you can also use a separate additional sieving device, into which the second fraction of PF2 particles is supplied via a transport device from the sieving device 6.

Claims (20)

1. A method for producing dispersed recyclate from a quartz composite by grinding molded products from a quartz composite, consisting of a polymer matrix and particles of inorganic filler introduced into it, including quartz particles, with a proportion greater than or equal to 60 wt.%, in which pre-crushed pieces of molded products crushed in a hammer mill (4) to form particles of a target size from 0.1 to 1 mm, forming a recyclate. 2. The method according to claim 1, characterized in that a fraction of particles containing recyclate-forming particles having the maximum target size is selected through a sieve. 3. The method according to claim 2, characterized in that the target particle size is 0.8 mm. 4. The method according to claim 1, characterized in that the first fraction (PF1) of particles with a maximum size, which is larger than the target size of the particles forming the recyclate, is taken from the hammer mill (4) through a sieve, and then in the subsequent sifting device (6) from From the first fraction (PF1) of particles, a second fraction (PF2) of particles containing recyclate-forming particles with a size smaller than or equal to the target particle size is selected and separated from a third fraction (PF3) of particles containing particles whose size exceeds the target particle size. 5. Method according to claim 4, characterized in that the maximum particle size is 5 mm, in particular 4 mm. 6. The method according to claim 4 or 5, characterized in that the sieve for obtaining the first fraction (PF1) of particles is a wire mesh sieve. 7. Method according to one of paragraphs. 4-6, characterized in that the target particle size is 0.8 mm. 8. Method according to one of paragraphs. 4-6, characterized in that the third fraction (PF3) of particles is returned to the hammer mill (4) for further grinding. 9. Method according to one of paragraphs. 4-8, characterized in that the movement of particles of the first fraction (PF1) crushed in a hammer mill (4) to the sieving device (6) and/or particles of the third fraction (PF3) from the sieving device (6) back to the hammer mill (4) carried out manually or using a transport device. 10. Method according to one of paragraphs. 4-9, characterized in that in the sieving device (6) or in an additional sieving device from the second fraction (PF2) of particles by sieving, a fourth fraction (PF4) of particles with a maximum size smaller than the target particle size is obtained and separated a fifth fraction (PF5) of particles containing particles forming the recyclate. 11. Method according to claim 10, characterized in that the maximum size of the fourth fraction (PF4) of particles is 0.1 mm, in particular 0.2 mm. 12. Method according to one of paragraphs. 4-11, characterized in that a mesh sieve is used to sift the first fraction (PF1) of particles and/or to sift the second fraction (PF2) of particles. 13. The method according to one of the previous paragraphs, characterized in that pieces (3) of molded products are used containing particles of inorganic filler introduced into the polymer matrix with a proportion of ≥ 65 wt.%. 14. Method according to one of the previous paragraphs, characterized in that the pre-shredded pieces (3) of the molded products have a maximum length of 40 cm, in particular 30 cm. 15. Method according to one of the previous claims, characterized in that the molded products are crushed manually or automatically using a grinding device to form pieces (3) of the molded products. 16. Method according to one of the previous paragraphs, characterized in that the pieces (3) of the molded products are fed into the hammer mill (4) manually or automatically using a transport device (2). 17. The method according to one of the previous paragraphs, characterized in that sinks are used as molded products. 18. Dispersed recyclate obtained by the method according to one of the previous paragraphs by grinding molded products from a quartz composite, consisting of a polymer matrix and particles of inorganic filler introduced into it, including quartz particles, with a proportion greater than or equal to 60 wt.%, to the target particle size 0.1-1 mm. 19. The use of dispersed recyclate according to claim 18 as an additive to the casting mass to produce a molded product from a quartz composite, in particular, a sink. 20. A molded product made from a quartz composite, in particular a sink, obtained using the dispersed recyclate according to claim 18.

Images