DE3023086A1 - METHOD AND DEVICE FOR PRODUCING THIN-WALLED MOLDINGS FROM THERMOPLASTIC PLASTIC - Google Patents

Description

Dipl.-Phys. Helnridi Seids. Patent attorney · Bierstadter Höhe 15 · P.O. Box 5105 ■ 6200 Wiesbaden 1 - ST (06121) 562022

Wiesbaden, June 19, 1980 Y 121 u / S / we

Bellaplast Maschinenbau GmbH 6501 Heidesheim

Method and device for producing thin-walled moldings from thermoplastic material

The invention relates to a method and an apparatus for producing moldings from thermoplastic Plastic, which is plasticized in a highly plastic state by heating and compressing until it is able to flow and extruded into the shape of a ribbon by extrusion from the die, that ribbon for stabilization on both Surfaces brought into contact with thermally conductive surfaces maintained at a predetermined temperature and in both belt surface areas cooled down to their carrying capacity

O and is solidified, the thus stabilized tape after one possible surface conditioning, which takes place by warming up the belt surface areas from the inside of the belt, is subjected to thermoforming to form the moldings.

The production of moldings from thermoplastic material 22 52 219 is already known from DE-AS 22 52 219 in such a method. In this process, the extruded Material is heated to a particularly high temperature and strongly plasticized,

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Dipl.-Phys. Heinrich Seids ■ Patent attorney · Bierstadter Höhe 15 · P.O. Box 5105 · 6200 Wiesbaden 1 · ® (06121) 562022

so that when extruding it is like pouring from the nozzle expires. Such extrusion at high material temperature. and a high degree of plasticization is only possible because the extruded tape according to DE-AS 22 52 219 immediately after leaving the slot die for stabilization caught on both of its surfaces by smooth stabilizing and cooling surfaces kept at a predetermined temperature and so in contact with these smooth, heat-conducting surfaces on both of its surfaces up to the

^ ability to be cooled and solidified. So in his The deformability of the strip that has cooled and solidified on the surface areas is not impaired by thermoforming, because namely on the way to thermoforming in both surface areas through thermal conduction from the

^The inside of the band at the extrusion temperature is restored or conditioned for a surface temperature suitable for thermoforming if the band is given the opportunity to do so between stabilization and thermoforming. However, it has been found to be disadvantageous that when extruding relatively thin strips and, in particular, when manufacturing very thin-walled shapes, the molding wall has stripes over the entire surface.

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3023088

Dipl.-Phys. Heinrich Seids. Patent attorney Bierstadter Höhe 15 P.O. Box 5105. 6200 Wiesbaden 1 $? (06121) 562022

In contrast, the invention is based on the object to provide a method and apparatus for stabilizing the ribbon coming out of the extruder die which the strip to be stabilized in the plastic state is mechanically transverse to its running direction on the chill roll is fixed.

This object is achieved according to the invention in that the tape pressed out of the extruder nozzle is stabilized guided on at least one surface over at least one roughened cooling surface and only in contact is brought with roughness peaks formed in these cooling surfaces.

It is based on the knowledge that the above-mentioned streaking is apparently due to the smooth training due to the cooling surfaces used to stabilize the cast strip. Due to the smoothly polished Execution of the cooling surfaces, the plastic film coming from the wide-wall nozzle can be smooth on this Do not interlock the surface in order to avoid the shrinkage stresses occurring transversely to the direction of movement, which occur during the Cooling arise to counteract. As a result of these shrinkage stresses, wrinkles form within the Band, which leads to the above-mentioned stiffening. Another disadvantage is the smoothly polished version

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Dipl.-Phys. Heinrich Seids, patent attorney. Bierstadter Höhe 15 · P.O. Box 5105 - 6200 Wiesbaden 1 - ® (0 6121) 562022

of the cooling roll surfaces in that they form monomer vapors between the extruded Belt and the surface of the cooling roller contribute to the formation of bubbles and thus also to the deterioration in quality contribute to the molding wall.

Surprisingly, it turned out that the Cooling rolls with a roughened surface of the extruded plastic film as a result of the roughness peaks Lends fixation during stabilization. This fixation of the tape to be stabilized transversely to The direction of travel is achieved in that the plastic film with the roughened surface geared to a cooling roller and thus counteracts the shrinkage stresses during stabilization. The surface imprint of the roughened roller on the strip to be stabilized is conditioned eliminated by the plastic core of the tape to be stabilized in the thermoforming device. Included there is a functional interaction, namely an apparently hydraulic action of the plastic material of the core on the shell-like Surface areas. This results in a very precise, particularly firm forging into the surface of the Tool stamp and thus to remove the rough

imprint of the roughened roller. The rough surface of the roller, which forms during machining, can also be advantageous

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Dipl.-Phys. Heinrich Seids. Patent attorney · Bierstadter Höhe 15 · P.O. Box 5105 · 6200 Wiesbaden 1 · 3? (06121) 56 2022

Absorb monomer vapors to avoid blistering counteract while stabilizing. Due to the advantageous punctiform support of the extruded Belt, the cooling of the belt is not carried out so abruptly, which in turn has a positive effect on the further Processability affects.

In a particularly advantageous manner, the tape pressed out of the extrusion nozzle can be on both surfaces guided over at least one roughened cooling surface and only formed in contact with these cooling surfaces Roughness peaks are brought.

In a further advantageous process step, following the initial stabilization, roughened Cooling surfaces a second stabilization by means of smooth cooling

-> areas are made. In another advantageous When making moldings from polystyrene, for example, the tape can be pressed out at around 24O C and the Stabilize on roughened cooling surfaces the first Stabilize at about 210 to 230 ° C.

The method according to the invention can be carried out with an apparatus comprising at least one extruder press is equipped, which is suitable to absorb thermoplastic material in granular form and continuously compress and heat until flowable; one

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Dipl.-Phys. Heinrich Seids · Patent Attorney ■ Bierstadter Höhe IS. P.O. Box 5105 6200 Wiesbaden 1 3ί (06121) 562022

Extruder nozzle connected to the extruder press or extruder presses, which is designed as a slot die and is provided with temperature control devices; a device connected to the extruder nozzle for Stabilizing the surface of the ribbon coming out of the extruder die and a thermoforming device to form it of formations in the band by deep drawing or embossing and devices for cutting out the moldings from the Tape.

Such a device should be characterized according to the invention in that the stabilization device with a roughened roller or a number of roughened rollers arranged one behind the other for the initial stabilization of the strip cast from the extruder nozzle is equipped at least on one surface thereof.

In a further advantageous embodiment, in the stabilization device following the roughened roller or rollers at least one or a number be arranged by smoothly polished rollers for secondary stabilization.

In a further possible embodiment, the in Direction of travel of the strip roughened rollers arranged one behind the other, each with a smaller depth of roughness

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3Q23086

Dipl.-Phys. Heinrich Seids · Patent Attorney · Bierstadter Höhe 15 · P.O. Box 5105 ■ 6200 Wiesbaden 1 ■ ® (06121) 562022

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be stepped to each other and the last roller arranged at the exit of the stabilizing device essentially correspond to a smoothly polished roller.

The roughened roller can, for example, have a roughness depth between 30 and 70 µm, preferably 50 µm.

However, the depth of roughness of the roller or rollers can vary from case to case to the material to be processed and the Material of the roller be adapted. In a particularly advantageous manner, the roughened, cylindrical circumferential surface the roller or rollers be surface-coated. Due to the good thermal conductivity of aluminum there are advantages if the cylindrical circumferential surface the rollers are made of aluminum. For such rolls with an aluminum surface, hard anodizing is an option, for example as such a surface finish.

The roughening of the roller circumference can be done in a wide variety of ways Wise done, for example mechanically, e.g. by sandblasting, but also in other ways such as For example, etching, eroding, metal spraying, etc. If the roughening may result in excessive roughness peaks arise, these can be easily flattened, for example using a fine-grain emery belt

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Dipl.-Phys. Heinrich Seids. Patent attorney · Bierstadter Höhe 15 - PO Box 5105 · 6200 Wiesbaden 1 · 3? (06121) 56 2022

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Are the rollers of the stabilizer on controllable cooling medium system connected, then leave the changes in the cooling effect resulting from the surface roughness can be easily adjusted by adjusting a correspondingly changed roller temperature. Another way to catch yourself changes resulting from the surface roughness In the cooling effect of the rollers, appropriate regulation of the roller speed in the stabilization device provides if the tape feed and thus also the stabilization device to a controllable, preferably continuously variable drive is connected.

Embodiments of the invention are described below explained in more detail with reference to the drawings. Show it:

Fig. 1 is a diagrammatic representation for the

Process sequence for the production of thin-walled moldings from thermoplastic Plastic;

2 shows a stabilization device for the extruded plastic strip; 3 shows a stabilization device in a

another embodiment; and FIG. 4 is a greatly enlarged partial section of a

roughened roller of the stabilization -25 - ■ direction. .

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Dlpl.-Phy ». Heinrich Seids · Paeentanwalt. Bierstadter Höhe IS PO Box 5105. 6200 Wiesbaden 1 S? (06121) 56 2022

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The process sequence shown in FIG. 1 for producing moldings from thermoplastic material consists from at least one extruder press 15, the thermoplastic material to one with facilities for Temperature control provided extruder nozzle 12 conveyed in the form of a slot nozzle. That from the extruder nozzle 12 incoming tape 13 is immediately after leaving the nozzle of a stabilization device 1O, which is later is described in more detail, supplied. In connection

IQ the stabilization device IO is followed by a device 16 for converting the continuous tape feed into a step-by-step feed. The plastic strip 13, which is now progressing step by step, is deformed in the thermoforming device, for example by deep drawing.

The molded articles molded in this way into the plastic band 13 are made from the material band in a punching device 19 13 cut. The remainder of the tape is directed into a collecting station 20 which contains a shredding device can. The granular material coming from the shredding device can then be fed via a metering device are fed back to the extruder press 15.

FIG. 2 shows an embodiment of the stabilizing device IO, which stabilizes the strip coming from the extruder nozzle 12 on its surface by cooling. The band 13 to be stabilized passes through a

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3Q23Q86

Dipl.-Phys. Heinrich Seids. Patent attorney Bierstadter Höhe 15. P.O. Box 5105 · 6200 Wiesbaden 1 · <S "(06121) 562022

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Arrangement of chill rolls 11, 14, of which the chill roll 11 roughened on its cylindrical peripheral surface and the cooling roller 14 on its cylindrical peripheral surface is executed smoothly polished. The roller 11 roughened on its surface, as can be seen in more detail in FIG is, by means of its flattened roughness tips 22, fixes the strip 13 coming from the extruder nozzle 12, which is still in a very plastic state. These roughness peaks 22 claw into the plasticized band 13 that it is so in its transverse direction is fixed in order to counteract occurring shrinkage stresses, which would cause a corresponding wrinkle formation. The roughened roller 11 can be made of, for example Aluminum have a roughness depth between 30 and 70 µm. The cylindrical peripheral surface of the roller 11 the E.g. made of aluminum, is roughened by means of sandblasting, the resulting sandblasting Roughness peaks slightly flattened mechanically, e.g. by means of a fine-grain emery belt, and then to be hard anodized.

As can be seen from Figure 2, a smoothly polished roller 14 is within a guide 23 of about 90 to the Center of the opposite roughened cooling roller 11 arranged to be adjustable. The dash-dotted one Arrangement of the roller 14 'and the dash-dotted course

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Dipl.-Phys. Heinrich Seids. Patent Attorney - BiersUdter Höhe 15 · Postfach 5105 ■ 6200 Wiesbaden 1 · S? (06121) 562022

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of the belt 13 show that by adjusting the smoothly polished rollers 14 'the looping of the cooling rollers 11 and 14 with the belt 13 and thus the length of the contact surface between the cooling rollers 11 and 14 and the band 13 is varied. Such a downstream smoothly polished roller 14 is to be used when the roughened roller 11 has a large depth of roughness. This downstream smoothly polished roller 14 is substantially the imprint of the rough surface of the roller 11 is eliminated. Following the stabilization device 10, the device 16 then follows, which converts a continuous movement of the belt 13 into a step movement.

FIG. 3 shows a modified embodiment of the stabilization device 10. Here, a strip 13 coming from the extruder nozzle 12 is also guided over a number of roughened rollers 11 arranged one behind the other for the purpose of stabilizing its surface, the roughness depth of which is so graded that the last , at the output of the stabilization device IO arranged roller has the roughness depth of a smoothly polished roller 14. The rollers 11 shown in Figure 3, which are _{adjustable according to the double arrows and 25 between the dash-dotted line} n> unc j the fully marked position,

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Dipl.-Phys. Heinrich Seids Patent Attorney Bierstadter Höhe 15 - P.O. Box 5105 6200 Wiesbaden 1 ST (0 6121) 56 20

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serve to vary the wrap angle of the tape 13 on the roller 11 or 14. This adjusts the length of the contact surfaces of the belt 13 so that a Stabilization depending on the thickness of the band 13 is always possible. In another embodiment, not shown the stabilization device IO consists only of evenly roughened rollers 11, which, like those in the Figures 2 and 3 shown embodiments are connected to a controllable cooling medium system. Depending on the The required degree of stabilization, the rollers 11 and 14 are cooled accordingly. The punctiform support of the Plastic tape 13 on the surface of the roughened roller 11 is too abrupt cooling on the surface of the band 13 prevented. This milder cooling of the band 13 results in greater shrinkage stresses avoided as a result of the deterrent.

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Claims (7)

3023081 PATENT ADVOCATE DIPL.-PHYS. HEINRICH SEIDS 62 Wiesbaden Bierstadter Höhe 15 P.O. Box 12068 Telephone (06121) 56 5382
Postal check Frankfurt / Main 1810 08 - 602 Bank Deutsche Bank 395 63 72 Nass. Sparkasse 108 00 30 65 Wiesbaden, June 19, 1980
Y 121 u / S / we Claims / 1.) Process for the production of moldings from thermo- plastic plastic, which by heating j and compaction to flowability in a strongly plastic State plasticized and extruded from the nozzle | is extruded in the form of a tape, this tape j to stabilize on both surfaces with heat j j conductive, maintained at a predetermined temperature Surfaces brought into contact and in both belt upper; surface areas cooled down to their load-bearing capacity
^un 3 is solidified, the band stabilized in this way after a ^{possible surface conditioning 1} , which is achieved by warming up the band surface area from the inside of the band! takes place, a thermoforming to form the moldings | is subjected, characterized in that the! the extrusion nozzle extruded tape during stabilization
on at least one surface over at least one roughened cooling surface guided and only in contact
is brought with roughness peaks formed in these cooling surfaces. 130061/0183 ORIGINAL INSPECTED 3023088 Dij> l.-Phys. Heinrich Seids, patent attorney Bierstadter Höhe 15. P.O. Box 5105 - “200 Wiesbaden 1 - β ¹ (06121) 562022 - 2 - 2.) The method according to claim 1, characterized in that the tape pressed out of the extruder nozzle on both surfaces over at least one roughened cooling surface guided and brought into contact only with roughness peaks formed in these cooling surfaces. 3.) The method according to claim 1, characterized in that subsequent to the initial stabilization on roughened Cooling surface a two-way stabilization is made by means of smooth cooling surfaces. 4.) Device for carrying out the method according to any one of claims 1 to 3, with at least one extruder press which is suitable for receiving thermoplastic material in granular form and continuously compressing and heating until flowable; an extruder nozzle connected to the extruder press or extruder presses, which is designed as a slot nozzle and is provided with devices for temperature control;
a device connected to the extruder nozzle for stabilizing the surfaces of the strip coming out of the extruder nozzle and a thermoforming device for forming shapes in the strip by deep-drawing or embossing and devices for cutting out the shaped articles from the strip, characterized in that the stabilizing roughening device (10) with a roughened roller _ (_ 11_) 130061/0183 3023088 Dipl.-Phys. Heinrich Seids · Patent Attorney · Bierstadter Höhe 15 · Postfach SlOS · 6200 Wiesbaden 1 - 3? (06121) 56 2022 or a number of roughened ones arranged one behind the other Rollers for the initial stabilization of the strip (13) cast from the extruder nozzle (12) at least one surface of which is equipped. 5.) Device according to claim 4, characterized in that in the stabilization device (1O) following the roughened roller (11) or rollers, at least one or a number of smoothly polished rollers (14) are arranged for second stabilization. 6.) Device according to claim 4, characterized in that one behind the other in the direction of travel of the band (13) arranged, roughened rollers (11) are stepped with each other, each with a smaller depth of roughness, and the last roller (14) arranged at the exit of the stabilizing device (10) is essentially a smoothly polished one Roller (14) corresponds. 7.) Device according to one of claims 4 to 6, characterized in that that the rough cylindrical peripheral surface of the Rolls (11, 14) is surface-treated. 130061/0183