DE102007060338A1 - Additive e.g. pigment, mixing and interfering method, involves leading additive within side extruder via conveying gap formed between worm shafts, where gap is extended at distance between outlines of worm shafts - Google Patents

Abstract

The method involves guiding a polymer melt in a double screw extruder (1) by two extruder shafts (4.1, 4.2). An additive e.g. pigment, is conveyed in a side extruder (2) by two worm shafts (14.1, 14.2) and supplied by a side opening (10) of the double screw extruder of a processing zone. The polymer melt and the additive are mixed with each other in the processing zone. The additive is led within the side extruder via a conveying gap formed between the worm shafts. The gap is extended at a distance between outlines of the worm shafts over an entire conveying length of the side extruder. An independent claim is also included for a device for the execution of a method for mixing and interfering an additive in a polymer melt.

Description

The The invention relates to a method for admixing and mixing a Additive in a polymer melt according to the The preamble of claim 1 and an apparatus for carrying out the Method according to the preamble of the claim 8th.

Around in the processing of polymer melts certain on the final product to get parked properties as well as appearance, it is known that the polymer melt additives are added. such Additives such as additives or pigments must as finely distributed as possible be incorporated into the polymer melt, thus becoming a homogeneous Structure of the used for further processing polymer melt to reach.

For example, from the EP 0 995 567 A1 a method and apparatus for admixing and blending an additive in a polymer melt to produce a fiber reinforced thermoplastic. For this purpose, the polymer melt is passed through a plurality of treatment zones in a twin-screw extruder through two intermeshing extruder shafts. In one of the treatment zones opens a side extruder, which has two intermeshing screw shafts, through which a filler is supplied via a side opening of the twin-screw extruder of the polymer melt. For this purpose, the worm shafts of the side extruder are held next to one another in a housing and connected to a drive via a drive end. When using two intermeshing screw shafts, it has been found that, for example, after admixture and mixing in of pigments, the polymer melt has several agglomerates of additives which were not dissolved in the polymer melt. However, such agglomerates or compaction of the additives lead due to the lack of homogenization and disbonding within the melt to inferior qualities in the final product.

From the DE 40 39 857 A1 a method and a device is known in which such a problem has already been known and in which the remedy the additive is first mixed in a partial melt stream of the polymer melt. For this purpose, the additive is drawn in a twin-screw extruder and mixed with a polymer melt stream supplied to the twin-screw extruder through a side opening. In this case, only part of the total polymer melt to be mixed is fed into the twin-screw extruder, so that after mixing the partial melt stream with the additive, it is combined with the non-blended substream to form the main stream. The sub-stream provided with additives and the uninfected partial stream of the polymer melt are then subsequently mixed in a mixer. This known method and known device thus requires a very high expenditure on equipment in order to mix the additive with the polymer melt. In addition, melting of the polymer melt initially takes place, since the polymer can only be fed to the twin-screw extruder in melt form.

It It is an object of the invention to provide a method for admixing and mixing an additive in a polymer melt and a device to carry out the method of the generic Art to improve that the additive with high uniformity can be incorporated homogeneously into the polymer melt.

One Another object of the invention is to provide a method of incorporation and mixing an additive in a polymer melt as well to provide an apparatus for carrying out the method, which with high flexibility in different production processes can be used.

These The object is achieved by a method with the features of claim 1 and by a device with the features of claim 8 solved.

advantageous Further developments of the invention are characterized by the features and feature combinations the respective subclaims defined.

Of the Invention is based on the finding that the compaction and agglomerates of the additive in a polymer melt substantially on an excessive compression of the additive are attributed. According to the invention therefore the additive within the side extruder by a guided between the plug shafts formed conveying gap, which translates as the distance between the contours of the worm shaft an entire conveying length of the side extruder extends. Consequently There are no unwanted contact points between the worm shafts on, which inevitably leads to compression points in the additive would lead. This allows the additive in its predetermined form and structure substantially unchanged add the polymer melt. Despite the between the worm shafts formed conveyor gap is by combing the worm shafts with each other a uniform and continuous promotion and thus a dosed admixture of Ensures additives in the polymer melt. in this connection are overlaps of the worm shafts as well as the size the Fördespaltes each on the shape of the additive and consistency of the additive.

The Process variant in which the screw shafts for promotion of the additive in the conveying nip at a drive end are stored multiple times and driven synchronously, is special advantageous to a constant metering of the additive at to ensure the admixture in the polymer melt. This results in a substantially constant volume flow in the side extruder produced and via a side opening in the twin-screw extruder initiated.

The Process variant according to claim 3 provides a further improvement of the homogeneity of the polymer melt For this purpose, the polymer melt and the additive in the Treatment zone mixed by screw elements of the extruder shafts, which have a mixing gap between them. The merging gap extends as a distance between the extruder shafts over at least a section of the treatment zone, allowing a contact between the extruder shafts and thus undesirable compaction sites avoided during mixing of the additive in the polymer melt become.

Prefers Here is the process variant in which the polymer melt in an upstream treatment zone of the twin-screw extruder is melted from a granulate. Thus can be immediately after making a main melt stream therein Mix guided polymer melt with an additive.

It However, it is also possible that the polymer melt stream directly after, for example, a polymerization or polycondensation introduced into the twin-screw extruder and with an additive is mixed.

When Additive can be additives, pigments or dyes of the Polymer melt are added. Here, the additive also be given by means of a carrier material to the page extruder and the polymer melt are supplied. As a carrier material For example, a polymer melt can be in the same Use the composition of the main melt stream.

Around to enable a direct further processing of the polymer melt, is according to another variant of the method the Polymer melt and the additive after mixing in further Treatment zones mixed, degassed and discharged. Here can after discharging the polymer melt, this to a granulate, a profile, a film or a thread are processed.

The underlying object is with a device to carry out of the method solved by the contours of the screw shafts with a distance from each other in the housing of the side extruder are held, which distance itself as conveying gap over the total length of the worm shafts extends. Thus, you can the worm shafts inside the housing without mutual Contact to be operated.

to Ensuring a uniform over the entire length of the worm shaft extending distance is in accordance with an advantageous embodiment of Device according to the invention the drive end the worm shafts in the housing by a plurality of bearing elements rotatably mounted. This allows additional between the worm shafts supporting forces and thus Avoid compressive force acting on the additive.

to Realization of a compact and as small as possible construction of the side extruder are the bearing elements of the two worm shafts according to an advantageous embodiment of the invention Device offset in the axial direction of the side extruder to each other held in the housing. Thus, small screw overlaps can be realize in the worm shafts with correspondingly small diameters.

One synchronous drive of the screw shafts can be in particular by the development of the invention Achieving device in that the drive ends of the screw shafts connected together via a gearbox with an electric motor are.

In Depending on the type of additive, for example a paste, a powder or a liquid is present, the distance of the screw shafts is preferably to a conveying gap in the range of 0.1 mm to 5 mm.

Especially preferred here is the development of the invention Device in which the screw shafts each with a radial gap in the range of 0.1 mm to 5 mm with respect to a housing wall of the housing are held, which over the Length of the conveying gap extends. With that also between the worm shafts and the housing adjusting sealing gaps chosen such that no excessive compression between the worm shafts and the housing can act.

to Mixing of the additive with the polymer melt is the inventive Device improved so that the extruder shafts in the Side opening associated treatment zone screw elements have, which form a distance between them, which distance itself as a mixing gap over at least a part of the Treatment zone extends.

Of the Distance between the screw elements is preferred by formed a diameter step in the extruder shafts, so that a more uniform Free space within the extruder housing is created to without excessive Compressions mixing of the additives with the polymer melt to obtain.

The Diameter stage of the extruder shaft is preferred by a reduction the screw diameter in the range of 0.05 mm to 3.5 mm formed.

to Further treatment, the extruder shafts have several shaft sections with screw elements or mixing elements. So lets For example, one between the side opening and a Feed opening in the extruder housing Melting zones as a further treatment zone. In addition, you can a plurality of shaft sections of the extruder shafts between the side opening and your discharge opening in the extruder housing a mixing zone, a degassing zone and a discharge zone as another Form treatment zone.

The inventive method and the invention Device can be used for all common polymer melts based on polyester, polyamide or polyolefins. By the side feeding of the additive into a main melt stream In addition, you can perform quick changes of additives. Elaborate cleaning is not required. By the inventive method and apparatus of the invention are preferred high quality polymer melts with additives Mistake.

The inventive method and the invention Device will be described below with reference to some embodiments with reference to the attached figures closer explained.

It represent:

1 schematically a cross-sectional view of a first embodiment of the device according to the invention for carrying out the method according to the invention

2 an enlarged section of the treatment zone for admixing and mixing of the additive in the polymer melt of the embodiment 1

3 schematically a cross-sectional view of another embodiment of the device according to the invention

In 1 and 2 a first embodiment of the device according to the invention for carrying out the method according to the invention is shown schematically in a cross-sectional view. 1 shows the embodiment in an overall view and 2 in a partial view in the region of the treatment zone for adding and mixing an additive in a polymer melt.

in this respect no explicit reference to any of the figures made is, the following description applies to both figures.

The embodiment according to 1 and 2 shows a twin-screw extruder 1 with two in an extruder housing 3 guided extruder shafts 4.1 and 4.2 , The extruder shafts 4.1 and 4.2 are at one end with an extruder drive 11 connected and driven synchronously. The extruder shafts 4.1 and 4.2 have a plurality of shaft sections that are in different screw elements 6 and mixing elements 7 are executed. The screw elements 6 and the mixing elements 7 the extruder shafts 4.1 and 4.2 are held overlapping each other so that the extruder shafts 4.1 and 4.2 combing each other in the extruder housing 3 interact. At the in 1 illustrated embodiment are a total of five shaft sections 5.1 to 5.6 shown by way of example.

On a feed side of the twin-screw extruder 1 is a feed opening 8th in the extruder housing 3 formed, on which a hopper 12 is arranged. On the opposite side of the twin-screw extruder 1 is a discharge opening 10 in the extruder housing 3 intended. In a middle area of the twin-screw extruder 1 is a side opening 9 in the extruder housing 3 contain. The side opening 9 opens in the beginning of the shaft section 5.3 the extruder shafts 4.1 and 4.2 , The differently shaped shaft sections 5.1 to 5.6 the extruder shafts 4.1 and 4.2 in each case form a treatment zone in which the by the extruder shafts 4.1 and 4.2 subsidized medium in particular a polymer melt undergoes special treatments. The shaft section 5.3 the extruder shafts 4.1 and 4.2 forms the treatment zone 13.2 in which one over the side opening 9 supplied additive by the extruder shaft 4.1 and 4.2 added polymer melt is added.

To feed the additive is coaxial with the side opening 9 a side extruder 2 arranged, which in a housing 22 on the extruder housing 3 connected is. Inside the case 22 are two intermeshing worm shafts 14.1 and 14.2 arranged. The worm shafts 14.1 and 14.2 protrude with a free end in the side opening 9 of the extruder housing 3 in, at the opposite end, the worm shafts 14.1 and 14.2 wave-shaped drive ends 15.1 and 15.2 on. The drive ends 15.1 and 15.2 are by several bearing elements 16.1 and 16.2 rotatably in the housing 22 stored. The bearing elements 16.1 and 16.2 are in the case 22 held axially offset from one another. At the in 1 illustrated embodiment, the bearing element 16.1 for the drive end 15.1 formed by two spaced apart rolling bearings. The bearing element 16.1 the drive end 15.2 is also formed by two spaced rolling bearings. The four in the case 22 arranged rolling bearings are formed side by side in the axial direction.

The drive ends 15.1 and 15.2 are with their free ends on a gear 17 with an electric motor 18 connected. This will be the worm shafts 14.1 and 14.2 through the electric motor 18 and the gearbox 17 driven synchronously.

The side extruder 2 indicates on the drive end of the worm shafts 14.1 and 14.2 an insertion opening in 1 not shown in detail. About the insertion can be the side extruder 2 enter an additive, which by the rotation of the screw shafts 14.1 and 14.2 retracted and to the side opening 9 is encouraged.

To promote the additive is between the worm shafts 14.1 and 14.2 a gap is formed, acting as a conveying gap over the entire length of the screw shafts 14.1 and 14.2 extends.

In 2 is an enlarged view of the worm shafts 14.1 and 14.2 shown the conveyor gap between them 19 form. This is between the worm shafts 14.1 and 14.2 a gap formed in 2 is indicated by the capital letter A.

Opposite the case 22 have the worm shafts 14.1 and 14.2 also a distance, as a radial gap 20 also over the entire length of the worm shafts 14.1 and 14.2 extends. The distance between the worm shaft 14.1 and the housing 22 is marked with the capital letter R Thus, the worm shafts 14.1 and 14.2 in the case 22 of the page extruder 2 freely rotatably held. A contact between the worm shafts 14.1 and 14.2 as well as between the worm shafts 14.1 and 14.2 and the housing 22 does not take place. In order to promote the customary for polymer melts additives such as pigments such as titanium oxide or carbon black particles or color additives, an order of magnitude of the conveying gap of 0.1 mm to 5 mm and a radial gap of the same order of magnitude has been proven. The overlap of the worm shafts 14.1 and 14.2 is chosen such that a continuous and uniform promotion is guaranteed. Through the synchronous drive of the worm shafts 14.1 and 14.2 as well as the storage of stuck with the worm shafts 14.1 and 14.2 connected drive ends 15.1 and 15.2 is a uniform and high dosing accuracy in the feed of the additive in the twin-screw extruder 1 guaranteed.

In the treatment zone 13.2 for mixing the added additive have the extruder shafts 4.1 and 4.2 each screw elements 24 on, which are held at a distance from each other and a mixing gap 21 form. The distance between the screw elements 24 the extruder shafts 4.1 and 4.2 is marked with the capital letter V. The distance V extends substantially over the entire region of the shaft portion 5.3 so the extruder shafts 4.1 and 4.2 in the shaft section 5.3 have no mutual contact. The distance V between the screw elements 24 is through a diameter step 23 in the extruder shafts 4.1 and 4.2 reached. Here are the screw elements 24 opposite the other screw elements 6 a reduced outer diameter, so that a diameter step 23 formed. This results between the screw elements 24 and the extruder housing 3 likewise a radial gap, which in its order of magnitude is the size of half the intermixing gap 21 between the screw elements 24 having. The wave sections 5.3 the extruder shafts 4.1 and 4.2 are thus also freely rotatable in the extruder housing 3 held. The admixture and mixing of the additive in the polymer melt takes place in the treatment zone 13.3 without any compression points between the extruder shafts 4.1 and 4.2 and the extruder housing 3 ,

This in 1 and 2 illustrated embodiment illustrates an apparatus and a method in which initially a plastic granules is provided. The plastic granulate is poured over the hopper 12 and the feed opening 8th introduced and in a combined intake and melting zone, which serves as a treatment zone 13.1 is melted to a polymer melt. For this purpose, the shaft sections 5.1 and 5.2 the extruder shafts 4.1 and 4.2 screw elements 6 and mixing elements 7 on.

In the next stage is in the treatment zone 13.2 an additive via the side extruder 2 in the twin-screw extruder 1 introduced and mixed with the polymer melt. Subsequently, the polymer melt to further treatment into the subsequent treatment zones 13.3 . 13.4 and 13.5 guided. In the following treatment zones 13.3 to 13.5 extending to the discharge opening 10 extend, there is an intensive mixing, degassing and discharge of the polymer melt. These are the shaft sections 5.4 and 5.6 with snail elements 6 and mixing elements 7 Mistake. Subsequently, the polymer melt from the discharge opening 10 conveyed out. The polymer melt can then be processed depending on the process to a granulate, a profile, a film or a thread.

In 3 a further embodiment of the device according to the invention for carrying out the method according to the invention is shown schematically in a cross-sectional view. The embodiment according to 3 is in wesentli chen identical to the embodiment according to 1 , so that reference is made to the above description at this point and only the differences will be explained.

At the in 3 illustrated embodiment is in particular the first treatment zone 13.1 and thus the shaft sections 5.1 the extruder shafts 4.1 and 4.2 in the twin-screw extruder 1 designed differently. Compared to the previously described embodiment is at the feed opening 8th a melt line 25 coupled, through which a polymer melt the twin-screw extruder 1 is abandoned. The polymer melt is passed over the melt line 25 fed and the treatment zone 13.1 confiscated and conditioned. Subsequently, in the subsequent treatment zone 13.2 an additive via the side extruder 2 the polymer melt added. The admixture and mixing is identical to the embodiment described above.

This in 3 illustrated embodiment is thus particularly suitable to be included in a reflow stream in the polymer melt, so that the polymer melt can be mixed with an additive.

The Device according to the invention can thus be depending on requirements in any production processes for melt preparation and melt manufacturing use the inventive method perform.

1

Twin-screw extruder

2

Side extruder

3

extruder barrel

4.1 4.2

extruder shaft

5.1 5.2, 5.3, 5.4, 5.5, 5.6

shaft sections

6

screw elements

7

mixing elements

8th

feed

9

side opening

10

discharge

11

extruder drive

12

hopper

13.1, 13.2, 13.3, 13.4, 13.5

treatment zone

14.1, 14.2

worm shaft

15.1, 15.2

drive end

16.1, 16.2

bearing elements

17

transmission

18

electric motor

19

conveying gap

20

radial gap

21

Vermengungsspalt

22

casing

23

Diameter step

24

screw elements

25

melt line

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• EP 0995567 A1 [0003]
• - DE 4039857 A1 [0004]

Claims (18)

A method of admixing and mixing an additive in a polymer melt, wherein the polymer melt is fed in a twin-screw extruder through two intermeshing extruder shafts through a plurality of treatment zones, wherein the additive in a side extruder conveyed by two intermeshing screw shafts and via a side opening of the twin screw extruder one of Treatment zones is supplied and in which the polymer melt and the additive in the treatment zone are mixed together, characterized in that the additive is guided within the side extruder through a feed gap formed between the screw shafts, which is a distance between the contours of the screw shafts over an entire conveying length the side extruder extends. Method according to claim 1, characterized in that that the worm shafts promote the additive in the conveying gap at a drive end stored multiple times are driven and synchronously. Method according to claim 1 or 2, characterized that the polymer melt and the additive in the treatment zone be mixed by Schneckenelemete the extruder shafts between the have a mixing gap, which is a distance between the extruder shafts over at least one section the treatment zone extends. Method according to one of the preceding claims, characterized in that the polymer melt in an upstream Treatment zone of the twin-screw extruder melted from a granule becomes. Method according to one of the preceding claims, characterized in that the additive as additives, pigments or dyes is added to the polymer melt. Method according to one of claims 1 to 5, characterized in that the polymer melt and the additive mixed after mixing in other treatment zones, degassed and is discharged. Method according to one of claims 1 to 6, characterized in that the polymer melt after discharging into a granulate, a profile, a foil or a thread processed becomes. Apparatus for carrying out the method according to one of claims 1 to 7 with a twin-screw extruder ( 1 ) with two driven and meshing extruder shafts ( 4.1 . 4.2 ) in an extruder housing ( 3 ), wherein the extruder shafts ( 4.1 . 4.2 ) several shaft sections ( 5.1 - 5.6 ) with screw elements ( 6 . 24 ) and mixing elements ( 7 ) for forming a plurality of treatment zones ( 13.1 - 13.5 ), and with a side extruder ( 2 ) with two driven and intermeshing worm shafts ( 14.1 . 14.2 ) in a housing ( 22 ) connected to the extruder housing ( 3 ) in the area of one of the treatment zones ( 13.2 ), the free ends of the worm shafts ( 14.1 . 14.2 ) in a side opening ( 9 ) of the extruder housing ( 3 protrude, characterized in that the contours of the screw shafts ( 14.1 . 14.2 ) at a distance (A) from one another in the housing ( 22 ), which distance (A) as a conveying gap ( 19 ) over the entire length of the worm shafts ( 14.1 . 14.2 ). Device according to claim 8, characterized in that the worm shafts ( 14.1 . 14.2 ) wave-shaped drive ends ( 15.1 . 15.2 ), which by several bearing elements ( 16.1 . 16.2 ) in the housing ( 22 ) are rotatably mounted. Device according to claim 9, characterized in that the bearing elements ( 16.1 . 16.2 ) of the two worm shafts ( 14.1 . 14.2 ) offset in the axial direction to each other in the housing ( 22 ) are held. Device according to one of claims 8 to 10, characterized in that the drive ends ( 14.1 . 14.2 ) via a transmission ( 17 ) with an electric motor ( 18 ) are connected. Device according to one of claims 8 to 11, characterized in that the worm shafts ( 14.1 . 14.2 ) a conveying gap ( 19 ) in the range of 0.1 mm to 5 mm. Device according to one of claims 8 to 12, characterized in that the worm shafts ( 14.1 . 14.2 ) each with a radial gap ( 20 ) in the range of 0.1 mm to 5 mm with respect to a housing wall of the housing ( 22 ), which extends over the length of the conveying gap ( 19 ). Device according to one of claims 8 to 13, characterized in that the extruder shafts ( 4.1 . 4.2 ) in the side opening ( 9 ) associated treatment zone ( 13.2 ) Screw elements ( 24 ), which have a distance (V) between them, which distance (V) is in the form of a mixing gap ( 21 ) over at least a part of the treatment zone ( 13.2 ). Apparatus according to claim 14, characterized ge indicates that the distance (V) between the screw elements ( 24 ) of the extruder shafts ( 4.1 . 4.2 ) by a diameter step ( 23 ) in the extruder shafts ( 4.1 . 4.2 ) is formed. Apparatus according to claim 15, characterized in that the diameter stage ( 23 ) of the extruder shaft ( 4.1 . 4.2 ) by reducing the screw diameter of the screw elements ( 24 ) is formed in the range of 0.05 mm to 3.5 mm. Device according to one of claims 8 to 16, characterized in that one of the shaft sections ( 5.1 . 5.2 ) of the extruder shafts ( 4.1 . 4.2 ) between the side opening ( 9 ) and a feed opening ( 8th ) in the extruder housing ( 3 ) a melting zone as a further treatment zone ( 13.1 ). Device according to one of claims 8 to 17, characterized in that a plurality of shaft sections ( 5.4 to 5.6 ) of the extruder shafts ( 4.1 . 4.2 ) between the side opening ( 9 ) and a discharge opening ( 10 ) in the extruder housing ( 3 ) a mixing zone, a degassing zone and a discharge zone as further treatment zones ( 13.3 - 13.5 ) form.