CA2106649A1

CA2106649A1 - Roller unit for comminuting synthetic materials

Info

Publication number: CA2106649A1
Application number: CA 2106649
Authority: CA
Inventors: Joachim Wagner; Werner Rasshofer
Original assignee: Individual
Current assignee: Bayer AG
Priority date: 1992-09-24
Filing date: 1993-09-21
Publication date: 1994-03-25
Also published as: JPH06190827A; FI934156A0; DE4232014A1; BR9303875A; FI934156A; KR940006737A; EP0589321A1

Abstract

ROLLER UNIT FOR COMMINUTING SYNTHETIC MATERIALS

ABSTRACT OF THE DISCLOSURE

The present invention is directed to a novel roller unit for the comminution of various materials. More particularly, the roller unit comprises:
1) a roller, 2) a counter-block having a concave surface, 3) an intake gap having an inlet opening and an outlet opening which opens into a comminuting gap. Both of the gaps are formed between the outer surface of the roller and the concave surface of the counter-block. The intake gap is tapered from a maximum of 100 mm at the inlet opening to a minimum of 0.025 mm at the outlet opening The comminuting gap is adapted to maintain a shearing speed of 100 sec-1 to 20,000 sec-1.

Description

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ROLLEiR UNIT FOR COMMIINUTING SYNTHETIC MATERIALS
BACKGROUND OF THE INVENTION
The present invention relates to a roller unit for the comminution of synthetic materials or of composites and mixtures of various types which contain syntheticmaterials.
All processes for recycling synthetic materials generally include a comminution stage. The costs of the comminution stage substantially influence the economic viability of the recycling process and are generally decisive in determining whether the socially desired recycling of used synthetic materials can be successful. A
moderately priced comminution process is also desired, however, for organic, natural polymers such as cellulose (wood, straw).
The object was, therefore, to develop a roller unit which allowed for the efficient comminution of any synthetic materials, organic, natural polymers (such as cellulose; ~ ;
- e.g., wood and straw) and composites and mixtures of various types which contain synthetic materials and/or j~olymers. It is most preferred that the roller unit allows for the production of powder.
The comminution of such materials using grinders or extruders is already known. In the case of grinders the input materials must be considerably comminuted in advance - as a rule, shredded and then granulated. For very small grain sizes -20 ~ as are necessary for manyirecycling processes - grinders are too expensive, since in these machines it is only possible for small anounts to be processes. In manycases production of powder is only possible by means of cryogenic grinding. Due to ~i the refrigerants needed! this method is very energy-intensive.
For the comminution of used rubber also the use of extruders is known (see, - 25 e.g., (~ierman Offeniegungsschrift 3,332,629 and Janik et al, Int. Polym. Sci. Technol.
(1990) 17(3), T33/T37). But here too the materials must be comminuted in advance -as a rule, granulated. The formation of a bridge in the intake area of the extruder also causes difficulties in the case of materials which have only a iow density and which have a severely fissured surface, as a result of which continuous operation in the production of powder becomes difficult. The known grinding processes employ-ing extruders result in powders with a grain size in the range 300 ~um to 500 ,um.
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It is also known how to granulate pieces of used rubber using corrugated rollers. In this case, use is made of special corrugated roller units in order to subject parts of used tires to preliminary comminution for the grinding process which uses an extruder. In these cases minimal grain sizes are achieved of about 3 mm.
Surprisingly, it has now been found that these difficulties are overcome by a roller unit as described in greater detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a roller unit with an intake gap which tapers continuously, and Figure 2 shows a roller unit with an intake gap which tapers zonally.
DESCRIPTION OFTHE INVENTION
The present invention is directed to a roller unit for the comminution of any synthetic material, any organic, natural polymer or any composites and mixtures of various types which contain synthetic materials andtor natural polymers (which has a minimum density of 0.005 g/cm3). Organic, natural polymers include celluloses such as wood and straw. It is most preferred that the material is comminuted to a powder.
The key to the present invention is a roller unit comprising an intake gap whichis formed between the outer surface of a roller and a concave opposite surface of a counter-block. The intake gap is tapered from a maximum of 100 mm at its intake opening to a minimum of 0.025 mm, preferably from a maximum of 20 mm to a minimum of 0.05 mm, and most preferably, from a maximum of 10 mm to a minimum of 0.25 mm. In the comminuting gap proper which is connected thereto (and which is also formed between the roller surface and the counter-block surface), a shearing speed of 100 sec~' to 20,000 sec', preferably 1,000 sec~' to 10,000 sec~', is adjust-able.
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More particularly~, the present invention is directed to a roller unit for comminut-ing materials, having a minirnum density of 0.005 g1cm3, comprising.
1 ) a roller having an outer surface, 2) a counter-block having a concave surface, . .
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3) an intake gap having an inlet opening for receiving and compressing said materials and an outlet opening which opens into a comminuting gap, both of said gaps being formed between the outer surface o~ said roller and the - concave surface of said counter-block, and wherein said intake gap is tapered from a maximum of 100 mm at said inlet opening to a minimum of 0.025 mm at said outlet opening, and 4) an outlet through which passes comminuted material, a) said comminuting gap being adapted for maintaining a shearing speed of 10û sec~1 to 20,000 sec~1, and b) collecting the material so-comminuted from said outlet.
Since only one roller is used, the new rolier unit is simpler.in construction and less prone to disorders. The comminuting gap, which adjoins the intake gap, may extend over a relatively large part of the periphery of the roller, as a result of which a more effective comminution is ensured than in the case of a pair of rollers. As is 1~ customary with roller units, the roller is preferably made of metal. The concave opposite surface of the counter-block can, if necessary, be provided with plates made from alloys which are highly wear-resistant. This is particularly recommended when the materials to be comminuted contain abrasive fillers.
The new roller unit has proved to be particularly suitable for the comminution, and, in particular, the pulverization of chemically and/or physically crosslinked polyurethanes, polyureas or polyurethane ureas; in particular, in the form of soft foam materials. Soft foams generally cause particular difficulties in the comminution on account of their elasticity, since there is a danger of compressed flakes not being sufficiently comminuted and being pulled through the roller gap in this state. Surpris-~ ingly~ it has been found that the new roller unit eliminates this disadvantage.
Preferably the~roller unit is provided with an intake gap which is continuously tapered.
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As an alternative to this, the roller unit is provided with an intake gap which is ~ :
tapered zonally.
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Depending on the material to be comminuted, both embodiments can have their advantages. In the second case, it is possible that each zone has a constant gap . .
width; each zone may, however, also be tapered individually. The transitions between the individual zones may be abrupt; but continuous transitions can also be 5 advantageous in the comminution of certain materials. As a rule, the gap width of the comminuting gap proper has a constant gap width, the maximum preferably being that possessed by the intake gap at the point of transition to said comminution gap. . ..
Preferably ~he roller and/or the counter-block of the roller unit are provided with , tempering devices adapted to maintain an operating temperature in said intake gap - : .
10 and said comminuting gap of 0C to 200C. Heating of the roller unit, for example, by heating the roller and/or the counter-block, can, however, be advantageous for the : :
processing of certain materials. In many cases, it is more advantageous to cool the : .
roller unit, since as a result of the frictional heat arising, thermal damage could be caused to the material to be comminuted, or thermoplastics could even begin to become sticky ot molten, which would result in th`e unit becoming contaminated. ~
If it is sufficient to do so, the tempering means will only be provided in the ~ .
counter-block, since here no slip-ring seals, such as would ~e required in the case of the rotating roller, are necessary.
Use is preferably made of a roller with a surface structure of average peak-to- ; .
valley height (according to DIN 4768, 4762) ranging from 0.01 mm to 0.1 mm. An average peak-to-valley hight in this range prornotes drawing of the material into the :.:
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intake gap and the comminution of said material.
Use may also be made, however, of other roller surfaces - for example, polished, etched, corrugated or granular.
I n accordance~with another particular embodiment of the new roller unit, roller .
and counter-block are periodically moved to and fro relative to one another in the axial direction of the roller in order to avoid the formation of grooves. It suffices if either the roller or the counter-block is moved. From a constructional point of view, it is advisable to move the counter-block to and fro, since this movement can be30 more simply brought about than it can in the case of the rotating roller.
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The new roller unit enables the materials comminuted thereby to be worked advantageously, specifically, material consisting of any synthetics with considerably differing densities can also be processed together; any rnixtures of thermop1astic and thermosetting synthetic materials can be processes, likewise, any mixtures of brittle 5 and elastic or flexible materials. Also mixtures consisting of thermoplastics and thermosetting plastics which previously could not be injection-molded can now beused advantageously. Above all, the new roller unit has proved to work economical.
In addition, the waste materials processed thereby can be further treated in par-ticularly economical manner.
Preliminary comminution is material-dependent and is mostly necessary only down to a particle diameter corresponding to the size of the intake opening of the intake gap.
Preferred synthetic materials for the comminution are thermop!astic or thermo-setting polyurethanes, polyurethane ureas or polyureas, and blends / composites 15 thereof with other synthetic materials; polycarbonate and polycarbonate blends with other synthetic materials; ABS and ABS blends with other synthetic materials; PVC
and PVC blends with other synthetic materials; SMA; polyamide and polyamide blends with other thermoplastic synthetic materials; polyolefins or polyolefin blends with other thermoplastic synthetic materials, polypropylene resins or polystyrene 20 resins being particularly preferred; and the like. Crosslinked rubbers may also be used.
The specified synthetic materials may be modified stili further. For instance, they may have cr~nventional mineral or organic fillers or reinforcing materials of fibrous, flat or other type in a continuous or discrete structure, and they may contain :
25 conventional processing aids or agents for improving mechanical surface character-istics or ageing characteristics. The specified synthetic materials or the article formed therefrom may also be lacquered or have been otherwise surface-modified by means of currentless or electrolytic metallization or plating, surface etching, plasma treatment and the like.

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Particularly preferred are thermoplastic or thermosetting polyurethanes, poly-urethane ureas or polyureas such as are described in Kunststoff-Handbuch, Volume7, "Polyurethane", Carl Hanser Verlag, Munich/Vienna, 1st Edition 1966 and 2nd Edition 1983. Such polyurethanes, polyurethane ureas or polyureas have a density5 of more than 0.5 kg/m3 and are, e.g. used in the construction of motor vehicles for manufacturing bumpers, for roofliners, rear parcel shelves, linings of luggage com-partments, door panelling, head~rests, seats, dashboards, consoles, in energy-absorbing foams and the like. In the furniture industry, cushions, mattresses and the like are manufactured from such materials.
Also particularly preferred are composite bodies or mixtures of said thermo-plastic or thermosetting polyurethanes, polyurethane ureas or polyureas with such materials as are used for the manufacture of composite bodies, whereby, these materials may be, e.g. glass mats, textiles, plastic foils, foamed foils, wooden bodies or even cellulose materials bonded by thermosetting plastic.
The comminuted material produced in this way, in particular powder, is suitable as raw material for the most diverse recycling techniques. Thermoplastics in powder form can be used for conventional thermoplastic processing and can be relativelyeasily processed and at the same time blended. Polyurethanes in this powder formare capable of being used advantageously in chemolytic processes such as 20 glycolysis, alcoholysis, aminolysis and hydrolysis. The powder form is also advan-tageous for extrusion-molding and injection-molding; this is particularly true of lacquered raw material. For use as filling material which is similar to or the same as a~matrix in polyurethane formulations, the powder form distributed as finely as possible is a necessary prerequisite for a high quality level and good surface charac-25 teristics. The polymer powders produced in this way can be used advantageously for thermal treatment methods.
The new roller unit is represented purely schematically in the drawing and is described in greater detail below. In Figure 1, the roller unit consists of a 1 m wide roller "1" of 600 mm diameter and a counter-block "2". Adjacent to a feed hopper30 "3", arranged above is an inlet opening 114~ of an intake gap ~5". The latter is ~;
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bounded by an outer surface "6" of roller "1", said outer surface exhibiting a peak-to-valley height of 0.05 mm, and a concavely curved opposite surface 7" of counter-block "2" of equal peak-to-valley height. At the inlet opening "4--, the intake gap "5"
has a gap width oF 200 mm, and it tapers continuously over an angular range oc of 80 to a gap width of 0.1 mm. Finally it merges directly with a comminuting gap "8n, which also has a gap width of 0.1 mm and which extends over an angular range of 100 of roller "1n. Roller "1" is provided with a tempering device "9 so that a flowable heating or cooling medium can flow through. A tempering device ~10n cabable of being flowed through by a heating or cooling medium is also arranged behind opposite surface "7" of counter-block ~2n.
In Figure 2, the roller unit consists of a 1 m widé~roller ~21~ of 600 mm dia-meter and a counter-block ~22~1. Adjacent to a feed hopper ~23~ arranged above is an inlet opening "24" of an intake gap "25~'. The latter is bounded by a smooth outer surface "26~ of rollern21" and a concavely curved opposite surface "27" of counter-block "22". At the inlet opening "24" the intake gap "25" has a gap width of 200 mm and tapers at the end of a first zone ~-31n to 10 mm, adjacent to which zone there is a rounded transition "32", which forms the entrance of a second zone "33" with aconstant gap width of 0.15 mm. The surface of zone "31" is smooth, that of zone "33" has a peak-to-valley height of 0.1 mm. Zone "31" extends over an angular range a of 30, and zone "33" over an angular range ~ of 40. Adjoining this with an additional gentle transition "34", is the comminuting gap proper "28" having a constant gap width of 0.15 mm over an angular range ,B of 110~. Roller "21" is pro-vided with a tempering device "29", so that flowable heating or cooling medium can flow through. A tempering device -30" capable of being flowed through by a heating or cooling medium is also arranged behind opposite surface "27" of counter-block22 .
The invention is further illustrated but is not intended to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified .

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EXAM PLES
Example 1 To the roller unit according to Figure 1 is supplied in a quantity of 130 kg/h, amaterial which has been pre-comminuted to a maximum dimension of not more than 100 mm consisting of flexible polyurethane foam having a density of individual par-ticles amounting to 0.05 9 per cm3. Roller "I" rotates at a speed of 30 min~', as a result of which a shearing speed of 9,400 sec~1 is generated in comminuting gap "8"
Tempering devices "9-- and "10" are fed with cooling water in order to maintain the temperature in intake gap "5" and in comminuting gap "B" below 60C. A powder of10 8 ~m mean grain size is obtained.
Example 2 To the roller unit according to Figure 2 is supplied in a quantity of 80 kg/h a material which has been pre-comminuted to a maximum dimension of not more than 100 mm, consisting of expanded glass-fiber-reinforced rigid polyurethane plates with 15 covering layers of aluminium foil. Roller "1" rotates at a speed of 30 min~, as a result of which a shearing speed of 6,300 sec~~ is generated in comminuting gap "28n.
Tempering devices "29" and "30" are fed with cooling water in order to maintain the temperature in intake gap "25" and in comminuting gap "28" below 60C. A powder with a grain size of 105 ~m is obtained. The pLllverized aluminium foil contained 20 therein can, if necessary, be separated by means of wind-sifting.
Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

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Claims

1. A roller unit for comminuting materials having a minimum density of 0.005 g/cm3 comprising:
1) a roller having an outer surface,

2) a counter-block having a concave surface,

3) an intake gap having an inlet opening for receiving said materials and an outlet opening which opens into a comminuting gap, both of said gaps being formed between the outer surface of said roller and the concave surface of said counter-block, and wherein said intake gap is tapered from a maximum of 100 mm at said inlet opening to a minimum of 0.025 mm at said outlet opening, and

4) an outlet through which passes comminuted material, a) said comminuting gap being adapted for maintaining a shear-ing speed of 100 sec-1 to 20,000 sec-1 therein, and b) collecting the material so-comminuted from said outlet.
2. The roller unit of Claim 1, wherein said intake gap tapers continuously.
3. The roller unit of Claim 1, wherein said intake gap has zones of differing gap width.
4. The roller unit of Claim 1, wherein said roller and/or said counter-blockare provided with tempering devices adapted to maintain an operating temperaturein said intake gap and in said comminuting gap of 0°C to 200°C.

5. The roller unit of Claim 1, wherein said roller has a surface structure of average peak-to-valley height in the range of 0.01 mm to 0.1 mm.

6. The roller unit of Claim 1, wherein said roller has a smooth surface.