APPARATUS AND METHOD FOR MIXING RECYCLING MATERIAL INTO A POLYESTER MELT

Abstract

Apparatuses and processes may be utilized for mixing used polyester into a polyester melt. In some processes an intermediate product stream is branched off from an intermediate stage in a virgin polyester production process. The intermediate product stream is then mixed with recycled polyester flakes in a dynamic mixer, where not more than 60% of a melting energy required to melt all the recycled polyester flakes is generated and/or supplied in the dynamic mixer. The mixture produced in this way is fed into a subsequent stage downstream of the intermediate stage and converted up to the desired degree of polycondensation. In this way, it is possible to physically reutilize used polyester or polyester waste.

Claims

1-17. (canceled)

18. A process for producing polyester using recycled polyester flakes, the process comprising: branching off an intermediate product stream from an intermediate stage in a virgin polyester production process; mixing the intermediate product stream with recycled polyester flakes in a dynamic mixer to form a mixture, wherein not more than 60% of a melting energy required to melt the recycled polyester flakes is generated and/or supplied; feeding the mixture into a downstream stage downstream of the intermediate stage and/or recycling the mixture into a reaction stage from which the intermediate product stream was taken; and converting the mixture up to a desired level of polycondensation.

19. The process of claim 18 wherein upon entry into the dynamic mixer the recycled polyester flakes have an average temperature of 0 to 200 C.

20. The process of claim 18 comprising supplying the intermediate product stream with at least 40% of the melting energy prior to the mixing, wherein the intermediate product stream transfers less than 40% of the melting energy to the recycled polyester flakes during a dwell time in the dynamic mixer.

21. The process of claim 18 comprising supplying the mixture with at least 40% of the melting energy after the mixing.

22. The process of claim 18 wherein a dwell time of the intermediate product stream and the recycled polyester flakes in the dynamic mixer is not more than 60 seconds.

23. The process of claim 18 wherein the mixing is performed at an absolute pressure of 3 to 100 mbar.

24. The process of claim 18 comprising filtering the mixture prior to attainment of the desired level of polycondensation.

25. The process of claim 18 wherein at least one of: the desired level of polycondensation is 100 to 200, or the mixture converted up to the desired level of polycondensation has an intrinsic viscosity measured according to ASTM D-4603-03 of 0.6 to 0.9 dL/g.

26. The process of claim 18 wherein 10% to 100% of an overall stream is branched off as the intermediate product stream at the intermediate stage.

27. The process of claim 18 wherein the intermediate product stream contains a diol.

28. The process of claim 18 wherein the mixture contains 5% to 60% by weight recycled polyester flakes.

29. The process of claim 18 comprising mixing the intermediate product stream and the recycled polyester flakes in the dynamic mixer with an additive selected from a group consisting of catalysts, stabilizers, dyes, flatting agents, optical brighteners, or mixtures thereof, wherein the additive is used in a proportion of not more than 5% by weight based on a resulting mixture.

30. An apparatus for producing polyester using recycled polyester flakes, the apparatus comprising: an apparatus for producing virgin polyester having multiple successive reaction vessels; and a dynamic mixer with a first inlet, a second inlet, and an outlet, wherein the first inlet is connected to a first reaction vessel of the multiple successive reaction vessels, wherein the second inlet is connected to an apparatus for dosage of bulk material, wherein the outlet is connected downstream to a second reaction vessel of the multiple successive reaction vessels.

31. The apparatus of claim 30 comprising an apparatus for comminution of recycled polyester that is connected upstream of the apparatus for dosage of bulk material.

32. The apparatus of claim 30 comprising: a first heat exchanger disposed between the apparatus for comminution of recycled polyester and the apparatus for dosage of bulk material; and a second heat exchanger disposed between the first reaction vessel and the dynamic mixer.

33. The apparatus of claim 30 comprising an apparatus for generating a reduced pressure that is connected to the dynamic mixer.

Description

[0110] The process according to the invention is to be elucidated in detail by the examples and figures which follow without restriction of the invention thereto.

[0111] FIG. 1 shows a flow diagram for a first embodiment of the process according to the invention, in which the intermediate product stream is branched off from the esterification reactor and accordingly consists of the esterification product with a degree of polycondensation of 1 to 6.

[0112] In the first embodiment in FIG. 1, at least a portion of an esterification product stream is branched off from an esterification reactor 101 as intermediate product stream 1. This intermediate product stream 1 is passed through a heat exchanger 210 and then fed to a dynamic mixer 200. As well as the intermediate product stream 1, the mixer has a second input stream, the recycled polyester stream 2. The recycled polyester stream 2 is fed from a reservoir vessel or a silo 220. The recycled polyester may be contacted here with a preheater 221, the preheater either being a separate unit or part of the silo 220. The dosage and hence the adjustment of the ratio of recycled polyester to intermediate product is effected with the aid of the metering apparatus 222. Also optionally envisaged is a further input stream 230 into the dynamic mixer 200, disposed at any position in the outer mixer shell. Additives and/or monomeric diol may be introduced into the dynamic mixer via this input stream 230. A vacuum apparatus 201 assures a desired reduction in pressure in the dynamic mixer 200.

[0113] After a short dwell time of the input streams in the dynamic mixer, a mixture 3 is formed, in which the recycled particles are distributed homogeneously in the intermediate product, but have not yet completely dissolved (homogeneous distribution of concentration, but no uniform, constant temperature).

[0114] The mixture is then introduced into a further reaction unit of the virgin polyester plant 4, namely into the postesterification reactor 102. The postesterification in the postesterification reactor 102 is the stage subsequent to the esterification in the esterification reactor 101 in the virgin polyester plant.

[0115] Unlike what is shown in the working examples, the mixture 3 may also be recycled into the same reactor stage from which the intermediate product stream 1 has been withdrawn beforehand, i.e. into the reactor stage 101 in the example according to FIG. 1, into the reactor stage 102 in the example according to FIG. 2, and into the reactor stage 103 in the example according to FIG. 3. Recycling into reactor stage 101 is preferred due to the excellent conditions in regard to mixing of the reactor content, residence time in this reactor stage and the large heat exchanging area available in this reactor stage.

[0116] The further conversion of the mixture up to higher molecular weights is effected in a pre-polycondensation reactor 103 which is the last process stage of the filtration apparatus 104. Condensation up to the desired degree of polymerization takes place in the final reactor 104 after passage through the filter apparatus 104. The melt can then be processed to small pellets in a pelletizer 105 and stored in a silo 107.

[0117] FIG. 2 shows a flow diagram for a second embodiment of the process according to the invention, in which the intermediate product stream from the postesterification reactor is branched off and accordingly consists of the postesterification product with a degree of polycondensation of 4 to 12.

[0118] FIG. 3 shows a flow diagram for a further embodiment of the process according to the invention, in which the intermediate product stream from the pre-polycondensation reactor is branched off and accordingly consists of the prepolymer with a degree of polycondensation of 20 to 50.