DE102006033507A1 - Plasticizer for use in diverse plastic injection molding and extrusion processes, has multi-zone screw made from alloyed tool steel with ion-nitrided, highly-polished surface - Google Patents

Abstract

The multi-zone screw is made of tool steel alloyed with chromium and/or nickel. Its entire surface is nitrided to a depth of 5 mu m or more, especially to a depth of 10 - 100 mu m. The surface is carbide-free. It is polished to a high luster. A typical surface hardness achieved is 40 HRC (Rockwell C). The tool steel quality is 1.2083 (or a comparable quality). Over the entire length of the screw tip, the projecting screw flight profile has a width expressed by 0.12 D2, where Dis the mean core diameter of the multi-zone screw. A number of quantified variants of this profile and radial dimensions are proposed. The cone angle of the main conical section exceeds 20[deg] and is especially in the range 21[deg] - 23[deg], especially at diameters exceeding 100 mm. The longitudinal screw profile comprising an induction zone, compression zone, extraction zone and extraction mixing zone, is detailed in terms of variants of its geometry and dimensions. During manufacture, nitriding by an ion-nitriding process, is accompanied by multi-stage heat treatment for surface hardening. An independent claim IS INCLUDED FOR the method of making the screw.

Description

The The invention relates to a plastic plasticizer according to the preamble of claim 1, a method for producing a Multi-zone screw of such a plastic plasticizer and uses of such a plasticizer.

Plastic plasticizing of the generic type have been for many years as essential components of plastic injection molding machines known and in practical use. Have in recent years they are also becoming more widely used in extruders, for example for highly productive ones Production of plastic pipes, cable sheaths or the like, in Plastic blow molding machines of the continuous type as well also in plastic reclaiming machines for the production of purified Plastic granules found from contaminated plastic waste.

Plasticizing the type in question here are about from the DE-OS 19 54 287 or the US 4,255,379 known. A generic plastic plasticizing is in the DE 42 38 277 C2 described.

To characterize the screw you can, for example, use their Schneckensteghöhe. The screw land height T results from the difference between the diameter D _{1 of} the screw and the screw core: T = (D 1 - D 2 ) / 2 (1)

Another frequently used core variable for distinguishing different screws or also different zones is the pitch S of the screw. This is understood to mean the product of factor H and screw diameter D ₁ . Within the scope of the invention, the term pitch S is understood to mean the distance from the beginning of a screw web to the beginning of an adjacent screw web. S = H × D 1 (2)

In addition, another frequently used variable for describing the screw characteristics is the so-called profile length length L. This is understood to be the length of the profile-carrying portion of the screw. The screw lengths L are often given in relation to D ₁ and are in today's screws generally 15-20 D ₁ , wherein the diameter D _{1 are} usually between 45 and 200 mm. Also important is the flight depth ratio G in the assessment of the screw quality. By default, today a flight depth ratio G of approximately between 2: 1 and 3: 1 has been proven.

at many snails now the Schneckenkern has no uniform Diameter.

Much more have in practice the injection molding of thermoplastic molding materials proven so-called three-zone screws. These can be due to the design and function over the entire length of the snail essentially distinguish three sections or zones, namely intake, compression and metering.

The first zone in the conveying direction of the screw is the feed zone or feed zone. It has the relatively largest screw land height T of all sections of the screw and serves to "pull in" the molding compound, for which purpose it is connected, for example, with a funnel. In the feed zone is between plasticizing and screw core usually the largest volume available, and the diameter of the screw core D ₂ is substantially constant in this zone. Since the screw core in the feed zone has the smallest diameter D _{2 of} all zones, the screw work in the feed zone is particularly large in known screws, since much material has to be moved in a relatively large volume.

The feed zone is followed by the compression zone, in which the diameter D _{2 of} the screw core widens conically. The reduction of the volume available in the compression zone between the plasticizing cylinder and the screw core results in a compression, ie compression of the material, during operation of the screw, which should occur without air inclusions and which serves to produce a melt of high homogeneity.

The third zone is followed by the so-called metering or exit zone at the compression zone. The screw core has a constant diameter D ₂ in the metering zone, so that in relation to intake and compression the metering zone has the lowest screw web height T. The metering zone has the functions of material transport and relaxation, ie reduction of the compression of the material.

According to the prior art, the three zones are usually in a very specific ratio relative to each other. The proportion of the intake is about 50%, that of compression about 35% and the proportion of Meteringzone about 15% of the profiled screw total length. The aspect ratios of the zones may vary depending on the application. So it is known for the processing of certain Polyblends to shorten the length portion of the collection to 40% and for it at changed proportion of the metering zone to carry out the compression with a length of about 45%. This prolongation of the compression has, inter alia, a strong influence on the pressure resulting from injection molding.

The Slope S of the snail can over the course of their length be formed differently, but is usually included known snails between 0.7 and 1.2 D. By a suitable Choosing the slope can influence the overall production result take the snail, as a larger snail slope significantly improves the plasticizing performance of a screw.

Even though now achieved with known snails quite good results in injection molding can be However, difficulties occur in the above-described screw design again and again on, if more complicated forms, for example, using an extensive sprue and hot runner system in the mold should be injection-molded, if particularly sensitive thermoplastics plasticized and processed or if sensitive Decorative materials, textiles, fabrics, films, etc. are back-injected should.

at the processing of relatively low-viscosity products and in the presence particularly long flow paths in the mold, it can in the standard three-zone worm Injection process easy to return the Melt in the screw flights come, what to a reduction of the quality or becoming unusable of the molding and to a negative impact of the injection molding machine for example, can lead by clogging the sprue. Especially if the plastic material of a strong compression is subjected and at the same time too low a material decrease took place at the tool, arises at the exit point of the material from the snail a backwater.

It Although now succeeded, this problem by the installation of a backflow valve at the front end of the snail more or less well in the grip to get, with the backflow stop slides forward during plastification and lets the melt through as it passes pressed backward during injection and so the antechamber shut off, but the usual Backflow locks are complex components which complicate the plasticizing unit, repair prone make and not unreasonably expensive.

Of Furthermore, there is a lack of the known three-zone screw at a for the processing of the Processing temperature of delicate substances sufficient Thermostatisierbarkeit along the snail. Screws are usually on the plasticizing cylinder mounted heating elements thermostatable. At the beginning of a casting or The entire screw is usually hit once to the desired melting temperature of the shot brought to processing plastic material, but then it is in essentially no additional heating more necessary because the temperature maintained by the so-called "snail work" becomes. The self-work of the screw (friction, shear rotation, self-rotation) delivers about 70% of the needed Warmth.

One Disadvantage of this heat is, however, that it is uncontrollable heat. Is the achievable temperature constancy of the thermoplastic material when processing sensitive materials, so both more sensitive Decoration materials as well as sensitive molding compounds, outside a relatively narrow tolerance interval of about ± 1 ° C deviation from a predetermined Setpoint, this has the consequence that at too high temperatures the fibers of the substance to be injected in the injection mold are melted or melted or at too low temperatures an insufficiently fluid, so too high viscosity, mass is injected. In both cases the manufactured back-injected molding scrap. Are at too high injection temperature, the fibers only once geled break or tear the entire material under stress. is the temperature of the molding compound has been too low, the cavities in the tool not enough filled and only weak vulnerabilities in the molding are preprogrammed.

The already mentioned above DE 42 38 277 C2 describes a comparison with the prior art improved plastic Plasitfiziereinrichtung, which does not require elaborate and vulnerable closure devices and at the same time the performance of the screw is improved.

Compared to the in this document described prior art is the present invention, the object of a particular in particular ih rer stability and thus the average cost, based on the practical life, further improved plastic plasticizer specify. Next is a process of making the crucial Component of such a plastic plasticizer, namely the multi-zone screw, be specified.

The former object is achieved by a Kuststoff plasticizing with the features of claim 1 and the second object by a method having the features of claim 29. Furthermore, practically significant uses of the here proposed Plastic plasticizer specified. Advantageous developments of the various aspects of the invention are the subject of the respective dependent claims.

In their device aspect closes the invention the essential thoughts that the functional and lifetime crucial part of the plasticizer forming multi-zone screw consistently made exclusively of high quality Tool steel, without any carbide insertions, perform. hereby are the inevitable in a carbide insert disturbances of closed tool surface avoided, according to investigations of the inventors a common cause of damage in hard practical use, especially in plasticizing of plastics blended with aggressive additives and impurities, represent.

Further includes the invention the essential thoughts, the surface of the used, according to the invention with chromium and / or nickel and / or cobalt alloyed tool steel as possible perfect quality to train to any sticking, baking or the like. of plastic as far as possible to avoid and at the same time points of attack for the mentioned components of the mass to be plasticized on the screw surface largely excluded. Special is the surface for this reason highly polished.

Finally includes the invention with the idea of a sufficiently deep nitridation of the steel surface, with the hard metal comparable surface hardness, but with improved toughness and excluding the above-mentioned disadvantages of cemented carbide inserts becomes. The nitriding depth should be at least 5 μm and is typically in the range between 10 and optionally over 100 microns, depending on Application requirements and cost limits lie.

Prefers is provided that the hardness is around 40 HRC. Further preferred is provided, the worm a tool steel of quality 1.2083 - if necessary also the quality 4122 - to manufacture.

Especially in plastics with processing technology higher degree of difficulty, such as in polycarbonates, polyethylene, polyvinyl chloride, various Polybiends as well as mineral and fiber filled Thermoplastics manages to be harmful To avoid temperature fluctuations. In particular, this succeeds by that to the known from the three-zone screw zones, ie directly to the metering zone, a fourth zone with conically tapering Helical core resulting in increasing auger height as metering mix zone followed This will be between metering zone and the according to the prior art itself at the metering zone immediately adjacent screw tip relatively large additional volume provided as Homogenisierungsraum, so it on the one hand to a better relaxation of the melt comes and on the other hand if there is insufficient material removal at the tip of the screw Reservoir is present, which is the reaction of the entire snail significantly improved on a dynamic pressure. On top of that - how extensive Experiments have revealed - at a multi-zone screw according to the invention, a good communication between snail and mold takes place, so that special in multiple tools with sometimes very complicated hot runner system a backflow of the Melt can be avoided from the mold cavity in the screw antechamber without backflow preventer.

In a very convenient design of according to the invention closes in the conveying direction to the fourth or metering mix zone a fifth zone of substantially constant Screw flight height as a metering H zone. As the chosen one Name suggests, has the fifth Zone essentially the same task as the well-known metering zone, namely Homogenization of the relaxed melt, especially the intimate mixing of the melt components and to some extent also the re-compression of the molten material in preparation for the actual injection process. To meet this task profile it is preferred that the Metering II zone has a screw land height, that of the Schneckensteghöhe corresponds to the metering zone.

As already executed, includes to the metering zone in the snails according to the prior art the On the tip of the screw. In a preferred embodiment follows at a Multi-zone screw according to the invention not on the metering zone, but on the metering mix zone or, if available, a screw tip on the Metering II zone, in the conveying direction first a substantially cylindrical part and then a has tapered part which forms the tip. Through this Construction will essentially be an adaptation of the flow cross section reached on the injection volume and the sprue cross section, as in general the tool over a runner is connected to the screw tip or nozzle.

According to the invention, it may now be particularly advantageous if at least the substantially cylindrical part of the screw tip with helices This means that the fifth or metering II zone is laid on the screw tip, so to speak. Also, this inclusion of the screw tip as a so-called helical tip allows, among other things with otherwise the same length of the screw as in the prior art, the creation of a five-zone screw.

In the case the five-zone screw with integrated spiral tip, it is then again advantageous that the cylindrical part of the screw tip is substantially the same Has Schneckensteghöhe like the metering mix zone, leaving the first cylindrical section the helical point can perform exactly the same functions as described above at the MeteringrII zone. In particular, at same slug gap height the Metering II zone as in the metering zone additionally through the compression or compression compared to the previous one Metering mix zone trapped trapped air, leaving one of air inclusions extremely free Melting available posed.

In a further preferred embodiment, not only the cylindrical part of the screw tip is provided with helices, but also carries the tapered part of the screw tip helix. The spiral of the screw tip, in particular of the tapered tapered part, is a special profile, the nature of which is described below. The special profile is provided with so-called helices over the entire area. This area is tapered from the largest diameter to the top. The slope is at the beginning of the conical region 0.7 D ₂ and tapers to 0.1 D ₂ in the tip region.

In preferred embodiments of the inventive concept, it is provided that the screw tip has a screw land substantially over its entire length with a land width between 0.1 D ₂ and 0.15 D ₂ , preferably of 0.12 D ₂ , where d is the mean core diameter is the multi-zone screw and / or that it has a slope in the range between 0.85 D ₂ and 1.0 D ₂ and / or a web height in the range between 0.9 D ₂ and 1.1 D ₂ .

On the active side (in the conveying direction), the helix is preferably provided with a radius R of about 10 mm. The cylindrical part of the special screw tip is equipped in the most favorable embodiment with about 3 webs These webs generally have a smaller pitch than the standard zones. The slope should preferably be 80%, ie 0.8 D ₂ .

In A further preferred embodiment provides that a first radius at the free end of the screw tip facing active flank of the screw flight at least by a factor of 2, preferably by a factor of 3 to 4, is greater than a second radius at the end of the screw facing passive edge of the screw land. One for typical screw dimensions appropriate execution provides that the first Radius between 8 and 12 mm, preferably 10 mm, and the second radius between 2, 5 and 5 mm, preferably 3 mm.

Around the parameters of the fifth Zone quickly and easily to be able to adapt to certain injection molding problems, is it is useful if the worm or helical tip at the front end of the worm interchangeable, for example unscrewable, is executed.

In a current state of knowledge of the inventors preferred embodiment of Invention is provided that the cone angle of a conical main part the screw tip more than 20 °, in particular with a diameter of the multi-zone screw of more than 100 mm between 21 ° and 23 °, is.

Under However, certain operating conditions can also be a point angle in the Range between 16 ° and 20 ° advantageous be, especially for smaller multi-zone screws with a medium Diameter of well below 100 mm.

Of Further, it is preferred if the between snail tip and Cylinder head provided axial gap on the type of thermoplastic to be processed is tuned. By this is meant that at very light flowing Plastics, for example polyethylene, the axial gap preferably on 1.2 to 1.5 mm, while with thermoplastics mean flow behavior a gap of 1.5 to about 2 mm is advantageous. On the other hand, with thermoplastics with difficult or poor flow properties a gap of approx. 2 up to 3 mm. It is advantageous, as already indicated, that the gap dimension can be changed, for example by means of the worm shaft accordingly adjustable Slices. The radial gap especially in the worm tip area is in a preferred embodiment of constant width.

Furthermore It is also advantageous, the cylinder head with a special To provide armor. Therefor appear due to lengthy basic experiments in particular Stellite suitable.

The great advantages of the inventive screw concept arise not only from the basic zoning, but also from the careful matching of the zone parameters to one another and the zone properties relative to one another at the.

So the compression zone is expediently shorter than with standard screws. Their relative length fraction is between 22.5 and 35%, preferably between 25 and 30% and most preferably 27.5% the total length the four zones indentation, compression, metering and metering mix. is the compression longer, then the plasticizing performance of the screw is too narrow.

falls below the compression zone is less than 22.5%, then the compression of the melt too high. Especially with highly sensitive and sensitive thermoplastics can discoloration and burns occur.

Farther It is advantageous if the relative length of the third or third Metering zone between 10% and less than 15%, preferably between 13.5% and 14.5%, and more preferably 13.75%, of the total length of the four zones feeder, compression, metering and metering mix is. Thereon follows that according to the invention also the Metering zone formed shorter is as in the prior art. In particular, it results the advantage that the shorter channel improves the plasticizing performance of the screw. Is the proportion the metering zone is less than 10%, then the auger stops the rear area air on. The melt is enriched with gas bubbles. Especially in the case of sensitive thermoplastics, the melt quality will be negative affected. For example, it can cause streaking come the moldings. On the other hand, if 15% is exceeded, then one can undesirable Friction occur, the shear effect can be too high, and the Melting temperature can no longer be precisely controlled.

Is appropriate in the proposed multi-zone screw, the relative length fraction in the prior art at all not found fourth or metering mix zone between 10 and 20%, preferably between 14.5 and 18% and be particularly preferred 16.25% of the total length the four zones indentation, compression, metering and metering mix. These fourth zone, namely the metering mix zone, is also useful in the inventive screw design to be called negative compression. The fourth zone can be in one particularly advantageous embodiment exactly to the fifth be matched cylindrical zone of the helical tip.

Is the length fraction the fourth zone more than 20% of the total length of the four zones indentation, Compression, metering and metering mix, then it can happen that the fourth zone is not completely filled with melt during operation. It can be then deposits of pigments or additives in this area form. About that In addition, the mixing effect, especially in color additives, deteriorated become. is the length proportion On the other hand, less than 10% of the total length, then is usually a significant deterioration of the melt quality recorded. By the reduction of for the melt available Room can the melting temperatures of standard thermoplastics increase by 4 to 8 ° C. Also falls in these cases in general the melt homogeneity, especially with the addition of dyes, significantly worse.

The total length of the first four zones can, as known from the prior art, be about 15 to 20 D ₁ , although longer versions are possible. It is advantageous to choose screws with a total length of 20 to 25 D ₁ .

Also for the Length of additional Metering II zone, there are preferred benchmarks. The Metering II Zone should have an extra length rate between 5 and 15%, preferably 10%, based on the sum of lengths of indentation, compression, metering and metering mix. in this connection is explicit to note that specifying the relative length of the Metering II zone as well on the total length is related to the first four zones, so that, for example, in the presence a metering II zone, a total length of the five zones of between 105 and 115% results.

The Metering II zone thus unfolds especially in the specified length range their beneficial effects, because then a gentle melt processing with the most accurate, for the machining process required Temperatures possible is. additionally it should be emphasized that opposite Standard screws when using a Metering II zone according to the invention with color additives to melt a pigment savings of about 50% for the same pigment yield can be achieved.

The slope and screw land height of the respective zone of the multi-zone screw according to the invention also contribute significantly to the advantageous melt processing behavior. In the following, the information about the pitch and the flight path height are each related to a screw with D ₁ of 80 mm. As soon as the D ₁ value of the screw changes, values deviating from the stated grades and screw pitches may also be preferred. However, this is familiar to the person skilled in the art and will be considered by him in the screw design.

A preferred characteristic of the multisectional screws according to the invention is, for example, that the feed zone is less deep may be in worms according to the prior art. In advantageous embodiments, the draw-in zone has a pitch of 0.7 D ₂ to 1.1 D ₂ , preferably between 0.8 D ₂ and 1.0 D ₂ , particularly preferably a pitch of 1.0 D, and a substantially constant screw land height in the range of 7.0 mm to 20.0 mm, preferably between 7.5 mm and 15.0 mm and particularly preferably of 8.2 mm. If the screw land height and / or the slope of the feed zone are above or below the respective maximum permitted limit values of the largest areas, the result is that a high-quality melt can no longer be processed.

In a further advantageous embodiment, the compression zone has a pitch in the range from 0.7 D ₂ to 1.1 D ₂ , preferably between 0.8 D ₂ and 1.1 D ₂ , particularly preferably a pitch of 1.0 D ₂ and a screw land height decreasing in the conveying direction, which is between 9.1 mm and 5.9 mm, preferably between 9.1 mm and 6.9 mm and more preferably of 8.2 mm at the beginning of the compression to between 8.5 mm and 5.0 mm, preferably reduced to between 6.5 mm and 4.2 mm and more preferably 4.2 mm at the end of the compression.

The metering zone has in an advantageous embodiment, a slope of 0.7 D ₂ to 1.1 D ₂ , preferably between 0.8 D ₂ and 1.1D ₂ , more preferably a slope of 1.0 D ₂ and a substantially constant screw land height in the range of 4.0 mm to 6.5 mm, preferably between 4.0 mm and 5.5 mm, and particularly preferably 4.2 mm. The compliance with the specified preferred ranges contributes especially to the fact that the material relaxes, so its compression is reduced.

In a further preferred embodiment, the metering mix zone has a slope of 0.7 D ₂ to 1.1 D ₂ , preferably between 0.8 D ₂ and 1.0 D ₂ , particularly preferably a slope of 1.0 D ₂ and an increasing in the conveying direction screw land height, the between 3.5 mm and 6.5 mm, preferably between 4.0 mm and 5.5 mm, and particularly preferably from 4.2 mm at the beginning of the metering mix zone to between 5 , 2 mm and 10.1 mm, preferably between 6.2 mm and 9.8 mm and more preferably 9.7 mm, increases at the end of the metering mix zone.

By the special design of the pitch and the auger height of the metering mix zone according to the specified ranges, it is possible to melt very gentle to relax and additionally gently homogenize Furthermore, an excellent mixing effect is especially sensitive color additives to reach. If the limits of the ranges are over or under slope below this level, discoloration of the melt may occur. The performance data, for example the plasticizing performance (in grams per second), is corrupted and the good mixing effect of color additives deteriorates.

Becomes the specified auger height range leave, then can deviate too high a thermal Load of the melt, and in case of deviation down from inventive area can the melt quality deteriorate. This can be expressed, for example, in that Inhomogeneities occur color additives segregate, packaging or discoloration of the melt or streaks occur.

Similarly, there are design guidelines for the Metering II zone as well which should not be relinquished in order to avoid undermining the preferred desired effect of the invention. Thus, it is preferred that the Metering II zone has a pitch of 0.5 D ₂ to 1.0 D ₂ , preferably between 0.6 D ₂ and 0.9 D ₂ , more preferably a pitch of 0.8 D ₂ and a substantially constant screw land height in the range of 5.0 mm to 7.5 mm, preferably between 5.0 mm and 6.5 mm and particularly preferably of 5.2 mm.

When Materials for the production of the multi-zone screw according to the invention are all substances in question, the expert from the production of snails for the processing of thermoplastic molding compositions are known. Prefers include stainless steels, for example 4122.

The Screw design according to the invention finds extremely advantageous Application in the production of screws used for plasticizing of thermoplastic molding compositions in an injection molding plant for injection molding of decorative materials, textiles or fabrics serve.

always become clearer about it beyond the promotions of the market for a recycling concept for granules, from the Hinterspritztechnik or similar Applications come and therefore partly very high shares of Foreign materials included. Such kinds of granules are on injection molding machines with standard screws so far not readily process, as it is inevitable with insufficient temperature stability depending on structure and origin the decorative materials after a short time to burn the decorative parts in the screw cylinder area comes.

When using the proposed multi-zone screw for plasticizing thermoplastic Molding compounds to which are added from the back molding of decorative materials derived decorative materials or residues thereof containing recycled Gra nulate in a proportion of between 5 and 50 wt .-%, preferably 10 to 25 wt .-%, based on the total amount of the molding composition to be processed has now been found that burning of foreign materials can be avoided. In particular, when using the screw according to the invention, the known negative processing characteristics such. B. poor intake behavior, impossibility of continuous product production and bonding or caking of locking and pressure ring of the return flow blockage by burned or gelled decorative materials are completely eliminated.

following becomes the multi-zone screw according to the invention with reference to the attached Drawings based on an embodiment explained in detail.

In show the figures:

1 a longitudinal section through a multi-zone screw with integrated spiral tip

2 the cut out 1 omitting the webs to better clarify the sequence of zones and their structure and

3 the detail "X" off 1 in an enlarged view.

At the in 1 illustrated multi-zone screw 10 it is a five-zone screw with integrated spiral tip. The multi-zone screw 10 has a plasticizing cylinder 20 with a diameter D and a substantially cylindrical screw 30 with a smaller diameter, which has a worm core 40 and attached to the outer surface thereof and closely to the inner wall of the plasticizing cylinder 20 adjoining snail bars 50 has that spiral around the worm core 40 run around and in conveying direction F rise.

The snail's core 40 with its webs or helix 50 is in the plasticizing cylinder 20 rotatably mounted and can by means of a device, not shown, on the flange or on the coupling, for example in the shaft journal 60 the core diameter 30 engages motor, for example electrically or hydraulically driven, wherein it rotates in the illustrated case in operation counterclockwise to move material in the conveying direction F.

At the front end of the plasticizing cylinder 20 is in the present example via a threaded flange or a screw connection a replaceable tip 70 attached.

Between plasticizing cylinder 20 and snail core 40 are due to the longitudinal direction of the screw 10 different, sectionally constant or varying, diameter D _{2 of} the screw core along the screw several zones of different screw land height T provided as best in 2 It can be seen where the webs and the plasticizing cylinder have been omitted to illustrate the sequence of zones and the diameter changes are unrealistically exaggerated.

The profile region length L of the illustrated embodiment of a screw according to the invention is, for example, 20 D ₁ . In the conveying direction you can now see the following successively arranged zones with different screw web height T: First you see a first zone 80 with substantially constant diameter D _{2 of} the screw core 40 , This feed or feed zone 80 is usually associated with a material feeder, not shown, such as a hopper, for the supply of plastic granules or molding compound components. The length of the feed zone 80 is in the example chosen about 8.5 D ₁ , which corresponds to a share of about 42.5%, based on the profile length L shown.

To the intake zone 80 closes in the conveying direction, a second zone with conically widening Schneckenkern and decreasing Schneckensteghöhe as a compression zone 90 at. The length of the compression zone 90 is in the example shown about 5.5 D ₁ , which accounts for a share of about 27.5%, based on the length L of 20 D ₁ .

Following the compression 90 is a third zone with a substantially constant helical pitch as a metering zone 100 to recognize. The length of the metering zone 100 is about 2.75 D ₁ , corresponding to a share of L of 13.75%.

The fourth zone follows the metering zone 100 a zone with increasing screw land height as a metering mix zone 110 , The length of the zone 110 in the example chosen is about 3.25 D ₁ , corresponding to a share of 16.25% of L.

To the metering mix zone 100 is a snail tip 70 Placed interchangeable via a flange or a thread The spiral tip 70 has in the conveying direction initially a substantially cylindrical part 71 followed by a tapered part forming the point 72 on. Both parts are with spirals or screw flights 50 Mistake.

The cylindrical part 71 the snail tip 70 has in the present example a length of about 2 D ₁ , corresponding to an additional 10% share, based on the length L, as well as substantially the same screw land height as the metering mix zone. The top part 71 can therefore also be called fifth zone or metering II zone 120 be designated.

The pointed part 72 the snail tip 70 forms an exact angle of 22 ° and is also provided with a special profile.

How best of all 3 it can be seen, the entire spiral tip 70 wrapped by a plasticizing cylinder This corresponds to the substantially cylindrical part 71 the worm tip a portion of the plasticizing cylinder 20 while the tapered tapered portion 72 the snail tip 70 from a cylinder head 130 is enclosed, directly to the plasticizing cylinder 20 followed.

In the 3 Exemplarily entered dimensions (in each case based on the average diameter D _{2 of} the multi-zone screw), namely the screw land width b _S of 0.12 D ₂ , the screw land height h _S of 0.1 D ₂ and the (average) screw pitch s _S of 0.9 D ₂ represent orientation values for important parameters of a preferred embodiment of the tip area of the plasticizer 10/20. Also of importance is the ratio between the radii on the active flank and the passive flank of the screw flight (r _S1 / r _S2 ) in the cylindrical section the snail tip, which can not be read from the figure, but in the illustrated embodiment should be about 10/3.

In the present example, the angle formed by the inner wall of the cylinder head of 22 ° corresponds exactly to the angle of the part 72 the spiral tip is formed. This prevents leakage of the melt.

Furthermore, on the cylinder head 130 an axial gap 140 to recognize, with respect to the gap, ie its diameter to the processed thermoplastics, variably adaptable, for example by means of a disc, not shown on the worm shaft in the present example, the gap in thermoplastics with difficult flow properties at about 2 to 3 mm, while the radial gap 150 especially in the worm tip area at a constant 0.1 mm.

The Five-zone screw with integrated spiral tip allows a particularly advantageous Working with very low peripheral speed compared to the prior art at the same time very high melt output. It means that the worm can be rotated relatively slowly, e.g. only with 5 m / min and still melt quality, performance and homogeneity of the melt better than in known three-zone screws. In particular, by the low peripheral speed the self-work of the screw relatively low held, which in turn leads to a particularly accurate temperature stability the melt along ± 1 ° C the entire length of the snail with all the resulting benefits for processing more sensitive Materials leads to total Thus, the formation of uncontrollable heat according to the inventive screw concept significantly reduced.

Further Advantages of the multi-zone screw according to the invention consist in the fact that in addition to the increased performance a special Good mixing effect occurs with color additives. The so-called pigment yield is due to the metering mix zone following the metering zone as well as the homogeneity yield significantly improved compared to standard screws Result that one and the same thermoplastic material to achieve a comparable dyeing effect in a screw according to the invention much less color additives must be added as with standard snails.

A Another particularly advantageous effect of the exact Thermostatisierbarkeit the snail shows itself in a particularly low wall adhesion of the Materials.

One Sticking the melt can be largely avoided, as well as the entire screw has a much lower overall wear as conventional Spritzgießaggregate.

Not To forget is also the outstanding suitability of the new and inventive Slug concept for the processing of recycled granules from the back injection technique and the extremely good Suitability of the screws according to the invention for the Processing of PVC. About that In addition, the suitability for the use in large machines allerbestens.

10

 Multi-zone screw

20

 plasticizing

30

 core diameter

40

 screw core

50

 spiral or snail bars

60

 shaft journal for coupling

70

 screw tip

71

 cylindrical Part of the spiral tip

72

 pointed tapered part of the spiral tip

80

 entry or feed zone

90

 compression zone

100

 metering or homogenization zone

110

 Metering mix zone

120

 Metering II Zone

130

 cylinder head

140

 axial gap

150

 radial gap

F

 conveying direction

D

 Inner diameter of the plasticizing cylinder

Claims (38)

Plastics plasticizing, in particular as part of an extruder, a plastic blowing device, an injection molding machine or a Regranuliermaschine, comprising a plasticizing cylinder and a multi-zone screw having on its longitudinal extent a plurality of sections with different core diameters and / or cone angles and a screw tip, said Sections of the multi-zone screw in each case in cooperation with a defined embodiment of the wall and / or a heating of the plasticizing define a plurality of working zones of the plasticizing, each having a specific function, characterized in that the multi-zone screw made with Cr and / or Ni and / or Co alloyed tool steel and their entire surface carbide-free to a depth of 5 microns or more, in particular from 10 to 100 microns, nitriding-hardened and highly polished. Plastic plasticizer according to claim 1, characterized in that the surface of the multi-zone screw a Hardness of typically 40 HRC. Plastic plasticizer according to claim 1 or 2, characterized in that the multi-zone screw from 1.2083 quality tool steel or a comparable one. Plastics plasticizer according to one of the preceding claims, characterized in that the screw tip substantially over its entire length a screw land with a land width between 0.1 D ₂ and 0.15 D ₂ , preferably of 0.12 D ₂ , wherein D _{2 is} the mean core diameter of the multi-zone screw. Plastics plasticizer according to one of the preceding claims, characterized in that the screw tip substantially over its entire length has a screw land with a pitch in the range between 0.85 D ₂ and 1.0 D ₂ , wherein D _{2 is} the mean core diameter of the multi-zone screw is. Plastic plasticizer according to one of the preceding claims, characterized in that the screw tip substantially over its entire length has a screw land with a land height of 0.9 D ₂ to 1.1 D ₂ , wherein D _{2 is} the mean core diameter of the multi-zone screw. Plastic plasticizer according to one of claims 2 to 6, characterized in that a first radius at the free end of the screw tip facing the active edge of the screw flight at least a factor of 2, preferably by a factor of 3 to 4, is larger as a second radius on the passive end facing the screw end Flank of the screw bridge. Plastic plasticizer according to claim 7, characterized in that the first radius between 8 and 12 mm, preferably 10 mm, and the second radius between 2, 5 and 5 mm, preferably 3 mm. Plastic plasticizer according to one of previous claims, characterized in that the cone angle of a conical main part the screw tip more than 20 °, especially with a diameter of the multi-zone screw of more than 100 mm between 21 ° and 23 °. Plastic plasticizer according to one of the preceding claims, comprising a screw core and a helical web extending thereon and a constant screw diameter, wherein the screw core has longitudinal sections of different, sectionally constant or varying diameter, so that along the entire length of the screw several zones of different screw land heights are present namely, a first zone with a substantially constant screw flight height as the intake zone, followed by a second zone with continuously increasing screw core diameter as the compression zone and a third zone with a substantially constant screw flight height as the discharge zone and a fourth zone, the fourth zone (FIG. 110 ) is formed with decreasing the screw core diameter as a discharge mixing zone and to the discharge mixing zone ( 110 ) connects a screw section, which in the conveying direction (F) first a substantially cylindrical part ( 71 ) and then a conically tapering, before tip forming part ( 72 ), wherein the substantially cylindrical part ( 71 ) and the tip-forming part ( 72 ) with a screw bridge ( 50 ) are provided. Plastic plasticizer according to An 10 or 11, characterized in that the Schneckensteghöhe the Metering II zone ( 120 ) of the screw gap height of the metering zone ( 100 ) corresponds. Plastics plasticizer according to claim 10, characterized in that the cylindrical part ( 71 ) of the screw tip ( 70 ) has substantially the same screw land height as the metering mix zone ( 110 ), so he as Metering II zone ( 120 ) acts. Plastics plasticizer according to one of claims 10 to 12, characterized in that the screw tip ( 70 ) interchangeable, preferably unscrewable, is. Plastic plasticizing device according to one of claims 10 to 13, characterized in that the screw tip ( 70 ) at its tip an angle of between 16 ° and 20 °, preferably between 17 ° and 19 ° and more preferably of 18 °. Plastics plasticizer according to one of claims 10 to 14, characterized in that the relative length portion of the second or compression zone ( 90 ) between 22.5 and 35 percent, preferably between 25 and 30 percent, and more preferably 27.5 percent of the total length of the four zones indentation ( 80 ), Compression ( 90 ), Metering ( 100 ) and metering mix ( 110 ) is. Plastics plasticizer according to one of claims 10 to 15, characterized in that the relative length portion of the third or metering zone ( 100 ) between 10 and less than 15 percent, preferably between 13.5 and 14.5 percent and particularly preferably 13.75 percent of the total length of the four zones indentation ( 80 ), Compression ( 90 ), Metering ( 100 ) and metering mix ( 110 ) is. Plastics plasticizer according to one of claims 10 to 16, characterized in that the relative length portion of the fourth or metering mix zone ( 110 ) between 10 and 20 percent, preferably between 14.5 and 18 percent, and more preferably 16.25 percent of the total length of the four zones indentation ( 80 ), Compression ( 90 ), Metering ( 100 ) and metering mix ( 110 ) is. Plastics plasticizer according to one of claims 10 to 17, characterized in that the length of the additional Metering II zone ( 120 ) between and 15 percent, preferably 10 percent, based on the sum of the lengths of feeder ( 80 ), Compression ( 90 ), Metering ( 100 ) and metering mix ( 110 ) is. Plastics plasticizer according to one of claims 10 to 18, characterized in that the feed zone ( 80 ) has a pitch of 0.7 to 1.1 D ₂ , preferably between 0.8 and 1.0 D ₂ , particularly preferably a pitch of 1.0 D ₂ . Plastics plasticizer according to one of claims 10 to 19, characterized in that the feed zone ( 80 ) has a substantially constant screw land height in the range of 7.0 to 20.0 mm, preferably between 7.5 and 15.0 mm and more preferably of 8.2 mm. Plastics plasticizer according to one of claims 10 to 20, characterized in that the compression zone ( 90 ) has a pitch of 0.7 to 1.1 D ₂ , preferably between 0.8 and 1.1 D ₂ , particularly preferably a pitch of 1.0 D ₂ . Plastics plasticizer according to one of claims 10 to 21, characterized in that the compression zone ( 90 ) has a screw land height which decreases in the conveying direction (F) and which is between 9.1 and 5.9 mm, preferably between 9.1 and 6.9 mm and more preferably of 8.2 mm at the beginning of the compression at between 8, 5 and 5.0 mm, preferably reduced to Plastics plasticizer according to one of the preceding claims, characterized in that the metering zone ( 100 ) has a pitch of 0.7 to 1.1 D ₂ , preferably between 0.8 and 1.1 D ₂ , particularly preferably a pitch of 1.0 D ₂ . Plastics plasticizer according to one of the preceding claims, characterized in that the metering zone ( 100 ) has a substantially constant screw land height in the range of 4.0 to 6.5 mm, preferably between 4.0 and 5.5 mm and more preferably of 4.2 mm Plastics plasticizer according to one of the preceding claims, characterized in that the metering mix zone ( 110 ) has a pitch of 0.7 to 1.1 D ₂ , preferably between 0.8 and 1.0 D ₂ , particularly preferably a pitch of 1.0 D ₂ . Plastics plasticizer according to one of the preceding claims, characterized in that the metering mix zone ( 110 ) has a screw land height which increases in the conveying direction (F) and which is between 3.5 and 6.5 mm, preferably between 4.0 and 5.5 mm and more preferably of 4.2 mm at the beginning of the metering mix zone at between 5, 2 and 10.1 mm, preferably to between 6.2 and 9.8 mm and more preferably to 9.7 increases with at the end of the metering mix zone. Plastics plasticizer according to one of the preceding claims, characterized in that the metering zone II ( 120 ) has a pitch of from 0.5 to 1.0 D ₂ , preferably between 0.6 and 0.9 D ₂ , particularly preferably a pitch of 0.8 D ₂ . Plastics plasticizer according to one of the preceding claims, characterized in that the metering zone II ( 120 ) has a substantially constant screw land height in the range of 5.0 to 7.5 mm, preferably between 5.0 and 6.5 mm and more preferably of 5.2 mm. Method for producing the multi-zone screw a plastic plasticizer after one of the preceding claims, characterized in that the multi-zone screw nitriding in connection with a multi-step temperature treatment for hardening the screw surface is subjected. Method according to claim 29, characterized that the nitriding is carried out as ionitriding. Method according to claim 29 or 30, thereby marked that the multi-section temperature treatment following steps include: a) annealing with furnace heating up 780 ° C, subsequent cooling in the Oven at 10 grd / h to 650 ° C and then Let cool down in the air, b) stress relief annealing with warmth at 650 ° C and holding this temperature for 2 h, then cooling down in the oven at 500 ° C and hold for 1.5 h and then Cool-down the air, c) hardening with two-stage preheating at 850 ° C and Austenitizing at 1030 ° C for 30 up to 40 min d) quenching in hot bath or fluidized bed or in overpressure chamber with the greatest possible Speed. Method according to claim 31, characterized in that that preheating in the step of hardening in a first stage from 600 to 725 ° C, with a subsequent holding time from 1 h, and a second step from 725 to 850 ° C, with a subsequent Holding time of 1.5 h, takes place. A method according to claim 31 or 32, marked by a step following step d) e) starting, at 250 ° C and holding this temperature for 2 h, which is carried out in particular several times. Use of plastic plasticizer according to one of the claims 1 to 28 in an extruder. Use of plastic plasticizer according to one of the claims 1 to 28 in a plastic blow molding machine. Use of plastic plasticizer according to one of the claims 1 to 28 in an injection molding machine. Use according to any one of claims 34 to 36 for direct Production of a plastic product from contaminated feedstock, in particular plastic scrap. Use of plastic plasticizer according to one of the claims 1 to 28 in a plastic reclaiming machine for recycling Plastic waste.