DE4333221A1 - Process for decolouring substrates made from plastic, in particular synthetic fibres - Google Patents

Abstract

In a process for decolouring substrates made from plastics, in particular synthetic fibres, where the substrate is subjected to a treatment, it is provided that the substrate is decoloured in a pressure container by means of a fluid under supercritical conditions in the presence of an absorbent. <IMAGE>

Description

The invention relates to a method for decolorizing substrates Plastic, in particular synthetic fibers, according to the preamble of the claim 1.

Among supercritical fluids are those that are originally gaseous or to understand liquid systems and mixtures thereof, which correspond to appropriate change in pressure and change in temperature above their criticality point. Here such fluid systems take special Properties.

Supercritical fluids are already becoming versatile for extracting content substances from polymers or from natural products in laboratories and in the Technology used. In these cases, either the extract obtained is that Main goal of the application (hops) or what remains after extraction Good (coffee).  

It is also known to use supercritical fluids for dyeing textile substrates to use.

The object of the present invention is to demonstrate a method which it allows coloring using ecologically safe means of substrates made of plastic, in particular textile fabrics or Remove yarns or systems for dyeing the aforementioned substrates.

The features of claims 1 and 20 serve to achieve this object.

The invention advantageously provides supercritical fluids as Carrier medium for that to be removed from the material to be treated To use dye, the dyes or dye mixtures of the substrate to be removed are transferred to an absorbent.

The method is particularly suitable for decolorizing the following Plastics:

• 1. Removing false stains regardless of whether the substrate is in supercritical CO₂ or has been colored in a conventional manner,
• 2. Decolorization of production residues or processing of waste for the purpose Recycling of plastic,
• 3. Decolorization of yarns, flakes, knitted fabrics, fabrics, fleeces, strands or Foils in the present form or after dismemberment,
• 4. decolorization of compact plastics after shredding,
• 5. Decolorization of home textiles, clothing textiles, technical textiles in the present form or after dismemberment.

The treatment of the substrate in the autoclave can be static or dynamic or mixed static-dynamic.

With the static treatment, the goods to be decolorized are combined in one Pressure vessel with a fluid that is under supercritical conditions, brought into contact, with an additional special feature of the invention Absorbent is used in the pressure vessel. Tie unexpectedly Absorber substances such as activated carbon, diatomaceous earth, silica gel, molecular sieves, Zeolites, as well as cheap plastics originally on the colored goods existing dyes so solid that they are withdrawn from the system, whereby the cleaning effect is achieved.

Absorbent is also to be understood as meaning substances which are suitable which Adsorb dyes.

It can be provided that the pressure of the supercritical fluid ends treatment is gradually reduced. The gradual reduction of the Pressure has a positive effect on the transfer process of the dyes and intensifies the dye transfer to the absorbent.

The treatment of the substrate can be done in several stages or in several stages a flow-through apparatus in which the supercritical fluid and the absorbent is interchangeable.

The temperature of the supercritical fluid is preferably brought to a value within a range above 80 ° C to a short temperature set before the decomposition point of the substrate. The Working pressure of the supercritical fluid to a value of approx. 200 to 500 bar, preferably 300 to 440 bar.

Carbon dioxide is preferably used as the supercritical fluid. It can a mixture of different supercritical fluids can also be used.  

The flow rate of the supercritical fluid with dynamic treatment of the The number of substrates is preferably one to two times that in kg weighed substrate in liters / min.

The method is particularly advantageous in the case of synthetic fiber textiles applicable.

Another area of application is the decolouring of shredded materials Plastic waste.

Activated carbon is preferably used as the absorbent. But others too Absorbents, e.g. B. silica gel, diatomaceous earth, molecular sieves, zeolites or certain waste plastics, e.g. B. non-crystalline polypropylene, Polyethylene, PES residues, organic complexing agents or a mixture the aforementioned absorbents can be used.

The weight ratio of substrate to absorbent is preferably between 0.6 and 1.5.

The supercritical fluid can moderators, for. B. swelling agent Increase in solubility are added.

For cleaning pressure-contaminated contaminants inside lockable devices, in particular systems for dyeing substrates with a supercritical fluid is further provided according to the invention, the Introduce absorbent into the device and the device by introducing a to clean supercritical fluids. The invention can be advantageous Way also used to identify contaminated dyeing plants in the after Dyeing processes Dye residues remaining in parts of the system must be cleaned. For this purpose, an absorbent in the interior of the container, e.g. B. one Autoclaves at a suitable location, e.g. B. deposited on the floor, wherein then flows through the system elements with a supercritical fluid become. Any dye residues remaining in the system washed out and absorbed by the absorbent.  

Further advantageous features of the invention emerge from the subclaims forth.

The following are with reference to the drawings Embodiments of the invention explained in more detail.

It shows

Fig. 1 shows a pressure vessel for the static treatment of a substrate, and

Fig. 2 is a flow-through apparatus for dynamic discoloration of a substrate.

By varying the pressure and temperature conditions and / or the variation the composition of the supercritical fluid, a detachment (out Solution) of the dye from the substrate to be decolorized, whereby the dye simultaneously deposits on / into the adsorbent and thereby from the System is removed. Possibly. is the static treatment multiple times in several Apply cycles depending on the desired decolorization target.

According to this method, substrates made of plastic as well as in particular textile materials of various constitution and construction Synthetic fiber material, e.g. B. PES; PA, cellulose triacetate (CT), aramid, Polyethercetone (PEEK), polyphenylene sulfide (PPS), PE, polypropylene (PP), Cellulose acetate (CA) can be effectively decolorized.

In dynamic treatment, a flow device is used to flow through a material to be decolorized under supercritical Conditions, the goods to be decolorized and with absorber substance Mistake. Supercritical fluid acts with the over the treatment period Working pressure on the substrate. After depressurizing and draining the fluid  the decolorized goods can be removed.

Fig. 1 shows a high pressure system for static decolorization tests. The pressure vessel consists of a heatable steel autoclave 1 with a volume of 300 cm³, which is equipped with a stirrer 2 and a perforated steel cylinder 3 for receiving the goods. Gaseous carbon dioxide is produced by a pressure application system, e.g. B. a membrane compressor 4 compressed to working pressure.

The membrane compressor 4 receives the gaseous carbon dioxide from a CO₂ storage bottle 8 via a valve 9 and a filter 7 . A check valve 6 and a further shut-off valve 15 are provided behind the diaphragm compressor 4 . 5 denotes a manometer for checking the working pressure. The inlet and outlet 10, 12 of the steel autoclave 3 are each provided with a valve 14 , 16, the fluid being able to escape into the atmosphere via the valve 16 after completion of the treatment.

The basic sequence of the static decolorization tests is as follows:
For the decolorization process, a 2-4 g tissue strip is wrapped around the sample holder. Absorbent is placed on the bottom of the autoclave or between the tissue wraps (packed in bags).

At the start of the decolorization process, a filling pressure of 1 MPa is specified. while the system is being heated to working temperature and the stirrer is on 600-800 rpm set. After reaching the desired working temperature the fluid (gas) is compressed to the working pressure. After desired Decolorization time is carried out with stirring to atmospheric pressure in several stages or continuously expanding. After that, the tissue sample is put into the autoclave taken and measured colorimetrically or the residual dye content of the goods  determined by extraction and photometric determination.

The following textile substrates were used as sample material:
Polyethylene terephthalate (PES)
PES fabric, plain weave dyed with disperse dye
PES knitted fabrics (Trevira 2000), dyed with disperse dye
PES seat cover for automobiles, colored with disperse dye
Polyphenylene sulfide (PPS) multifilament, colored with disperse dye
Polypropylene (PP) fabric dyed with disperse dye.

Fig. 2 shows a schematic diagram of a flow-through apparatus for dynamic supercritical extraction of dyes.

The flow-through apparatus consists of an extraction container 20 which receives supercritical carbon dioxide via a line 22 , which flows through a filter 21 and a heatable restrictor 24 behind the extraction container 20 and can then optionally be fed back to the extraction container 20 during a recirculation. A moderator can be added via a line 26 . After completion of the treatment, the fluid can be blown off into the atmosphere via a line 28 and a valve 30 .

Examples No. 1-5 describe static decolorization tests, No. 6 ff static / dynamic decolorization tests.

example 1

1.12 g of red-colored PES fabric in the above autoclave, 2 g of polypropylene (PP) as an absorbent at the bottom of the autoclave;
Working pressure 280 bar, working temperature 130 ° C, treatment time 50 min.

Result: PP absorbed a lot of dye, tissue of colorimetric Brightness originally dL -49.3 with color shift to dL -53.0 extracted.

Example 2

1.3 g PES tissue, violet disperse-dyed, with 0.97 mg dye / g tissue is in the presence of 2 g of activated carbon for 50 min at 280 bar and 130 ° C. treated. After the expansion stages, the amount of dye on the fabric measured again. It now results in <0.01 mg dye / g tissue.

Example 3

2.2 g of PES knitted fabric containing 2.25 mg / g of red disperse dye treated with 1.5 g of activated carbon analogously to Example 2. At the end of the experiment contain <0.02 mg / g dye / g.

Example 4

• - 3.95 g gray-black PES automotive seat cover (without coating) with 4 g Activated carbon in an autoclave (a bag of 2 g activated carbon between the Fabric wrapped, a bag on the bottom)
• - treated statically at 300 bar and 135 ° C for 40 min,
• - then expanded pressure in several stages.
• - Repetition of the last two process steps mentioned.

Result after the first treatment phase: the colorimetric brightness of the Reverse compared to barium sulfate white standard is from original dL -66.7 to dL -37.1.

After a second treatment cycle, the brightness improves to dL  -31.7. The front shows a dL of -36.2 and -31.5 respectively Barium sulfate white standard.

Example 5

PES car seat cover becomes analogous to the first treatment phase of the example 4 cleaned at 280 bar and 140 ° C. Instead of CO₂, nitrous oxide is used (Laughing gas) used. A sample is obtained whose colorimetric brightness the back measured 35.5 compared to the original (opposite White standard barium sulfate -33.6). The front shows a brightness of dL 35.5 compared to the original front and dL -33.6 compared Barium sulfate.

Example 6

Approx. 0.1 g PES knitted fabric, dyed violet, with 0.7 mg dye / g Knitted fabric is cut into pieces measuring approx. 1 cm × 1 cm and 2 g Activated carbon (granules 0.4 mm to 0.8 mm particle diameter) in the Extraction container given.

After reaching the extraction conditions (e.g. 500 bar and 130 ° C the extraction good initially static for 10 minutes with supercritical CO₂ treated. Then the extraction material is dynamic for 30 minutes with 1 to 2 ml / min compressed CO₂ extracted under the same conditions. To When the extraction is complete, the temperature is reduced below 100 ° C and the remaining pressure released all at once.

Result: The PES knitted fabric to be decolored is completely decolored.

Example 7

0.1 g PES knitted fabric, dyed red disperse, with 1.4 mg dye / g knitted fabric extracted analogously to Example 6 in the presence of 2 g of activated carbon.  

Extraction conditions: 500 bar, 130 ° C bar, 3 minutes static, 30 minutes dynamic at 2 ml / min flow.

Result: The extracted pieces of the PES knitted fabric are almost complete discolored. There remains one in a few small places Minimal residual amount of dye, but below quantitative Detection limits.

Example 8

0.18 g PES knitted fabric, dyed fluorescent yellow, with 1 mg dye / g Knit is analogous to Examples 6 and 7 in the presence of 2 g of activated carbon extracted at a flow rate of 1.5 ml / min. You get one completely discolored sample.

Example 9

0.16 g of PES knitted fabric is as in Example 6 in the presence of 1 g Diatomaceous earth (cleaned and annealed) extracted dynamically. Extrac conditions as in Example 8. Result: amount of dye on the knitted fabric after extraction 0.16 mg / g knitted fabric. The diatomaceous earth has the knitted fabric detached dye is absorbed, which can be removed using acetone leaves, so that the absorber can be regenerated again.

Example 10

0.1 g of PES knitted fabric (see Example 6) is in the presence of 2 g of silica gel (average particle size 40 microns) extracted analogously to Example 2. Result: Stains unevenly decolored, amount of dye per g of knitted fabric now 0.05 mg. The  Silica gel has absorbed the dye detached from the knitted fabric, the can be removed by means of acetone so that the absorber starts to rain again can be cured.

Example 11

0.14 g of PES knitted fabric (see Example 6) is in the presence of 2 g of activated carbon extracted. Extraction conditions: 130 ° C, 500 bar, treatment time 30 Minutes static and 5 minutes dynamic at 1.7 ml / min. Result: The sample is almost completely discolored in some places. Residual amount of dye the sample <0.02 mg / g sample.

Example 12

0.18 g of PES knitted fabric (see Example 6) is in the presence of 2 g of activated carbon extracted. Extraction conditions: 100 ° C, 500 bar, 10 minutes static, 30 Minutes dynamically at 1 ml / min. You get a cleaned knitted fabric with only 0.11 mg of residual dye / g of sample.

Example 13

0.16 g of PES knitted fabric (see Example 7) is in the presence of 2 g of activated carbon extracted. Extraction conditions: 130 ° C, 200 bar, 10 minutes static, 30 Minutes dynamic with 3 ml / min. You get a cleaned knitted fabric with only 0.23 mg dye / g sample.

Example 14

50 mg of PES knitted fabrics (see Example 6) is in the presence of 2 g of activated carbon extracted. Extraction conditions: 130 ° C, 500 bar, 5 minutes static, 1 minute dynamically at 1.5 ml / min. A knitted fabric is obtained whose residual color amount of substance is below the detection limit.  

Example 15

0.12 g car seat cover, PES, gray-black colored, without coating, is in Extracted presence of 2 g of activated carbon. Extraction conditions: 130 ° C, 500 bar, 10 minutes static, 30 minutes dynamic at 1.8 ml / min.

Result: Colorimetry dL -36.2 compared to the starting material (front).

Example 16

0.2 g car seat cover, PES, gray-black colored, with coating, is in Extracted presence of 2 g of activated carbon.

Extraction conditions: 130 ° C, 500 bar, 10 minutes static, 30 minutes dynamic at 1.5 ml / min. Result: coating and PES material decolored evenly. Colorimetry: dL -34.8 compared to the front of the Source material.

Example 17

0.1 g polypropylene fabric, disperse colored blue, 4.2 mg dye per g Tissue is extracted in the presence of 2 g activated carbon. Extraction conditions conditions: 130 ° C, 500 bar, 10 minutes static, 30 minutes dynamic at about 0.9 ml / min.

A completely decolorized tissue is obtained.

Example 18

0.16 g Ryton multifilament (PPS), with C.I. Disperse Red 1 is colored in Extracted presence of 2.4 g of activated carbon.  

Extraction conditions: 130 ° C, 500 bar, 10 minutes static, 30 minutes dynamic at 1.8 ml / min.

Result: strand uneven, but almost completely discolored. Colorimetric data dL -5.5 compared to the original sample. The appearance corresponds to that of PPS filaments in their original condition.

Colorimetry (CIE-LAB system)

The method can also be used advantageously for cleaning devices or systems according to FIG. 1 or FIG. 2 that are contaminated inside with dyes and can be shut off in a pressure-tight manner. An absorbent is in the interior of the device, e.g. B. deposited on the floor or in suitable places in bags. A supercritical fluid is then introduced into the contaminated system and residual dyes are removed either statically or dynamically.

The supercritical fluid can be used after the treatment of the substrate or cleaning a dyeing system can be collected in a container and can be used advantageously for further decolorization processes. Furthermore, it is possible to remove the absorbent after completion of decolorization process to regenerate. When activated carbon is regenerated ther mixed, d. H. by heating the activated carbon. With silica gel is a cleaning provided with acetone. In this way, the absorbent can also be repeated be used for the decolorization process.

Claims (34)

1. A process for decolorizing substrates made of plastics, in particular synthetic fibers, the substrate being subjected to a treatment, characterized in that the substrate is decolored in the presence of an absorbent in a pressure vessel with a fluid which is under supercritical conditions. 2. The method according to claim 1, characterized in that the pressure and the temperature of the supercritical fluid during treatment is varied. 3. The method according to claim 1 or 2, characterized in that the Gradual pressure of the supercritical fluid at the end of the treatment is reduced. 4. The method according to any one of claims 1 to 3, characterized in that the treatment is carried out in several stages in several cycles. 5. The method according to any one of claims 1 to 4, characterized in that the substrate is treated in a flow-through apparatus, in which the supercritical fluid and the absorbent in time intervals are interchangeable. 6. The method according to any one of claims 1 to 5, characterized in that the temperature of the supercritical fluid to a value within a range above 80 ° C to the decomposition point of the Substrate is set. 7. The method according to any one of claims 1 to 6, characterized in that the working pressure of the supercritical fluid to about 200 to 500 bar, preferably 300 to 440 bar.   8. The method according to any one of claims 1 to 7, characterized in that supercritical carbon dioxide is used as the fluid. 9. The method according to any one of claims 1 to 8, characterized in that supercritical nitrous oxide is used as the fluid. 10. The method according to any one of claims 1 to 9, characterized in that a mixture of supercritical fluids is used as the fluid. 11. The method according to any one of claims 1 to 10, characterized in that that the residence time of the substrate in the pressure vessel at static Treatment between 20 and 120 min. is. 12. The method according to any one of claims 1 to 11, characterized in that the flow rate of the supercritical fluid at dynamic Treatment of the substrate numerically one to two times that in kg weighed substrate in liters / min. 13. The method according to any one of claims 1 to 12, characterized in that that the substrate consists of synthetic fiber textiles. 14. The method according to any one of claims 1 to 13, characterized in that that the substrate consists of shredded plastic waste. 15. The method according to any one of claims 1 to 14, characterized in that activated carbon is used as the absorbent. 16. The method according to any one of claims 1 to 14, characterized in that as an absorbent silica gel, diatomaceous earth, molecular sieves or zeolites be used. 17. The method according to any one of claims 1 to 16, characterized in that that as absorbent waste plastics, e.g. B. non-crystalline PP, Polyethylene, PES residues or organic complexing agents or a Mixture of aforementioned absorbents can be used.   18. The method according to any one of claims 1 to 17, characterized in that the weight ratio of substrate to absorbent is preferably between 1.5 and 0.6. 19. The method according to any one of claims 1 to 18, characterized in that the supercritical fluid moderators, e.g. B. swelling agent Increase in solubility are added. 20. Process for cleaning inside contaminated with dyes devices can be shut off in a pressure-tight manner by introducing an absorbent into the device and by introducing a fluid that is under supercritical Conditions stands in the contaminated vessel. 21. The method according to claim 20, characterized in that the pressure and the temperature of the supercritical fluid during treatment is varied. 22. The method according to claim 20 or 21, characterized in that the Treatment takes place in several stages in several cycles. 23. The method according to claim 20 to 22, characterized in that the Device flows through the supercritical fluid. 24. The method according to any one of claims 20 to 23, characterized in that the temperature of the supercritical fluid is above 80 ° C is set. 25. The method according to any one of claims 20 to 24, characterized in that the working pressure of the supercritical fluid to about 200 to 500 bar, preferably 300 to 440 bar. 26. The method according to any one of claims 20 to 25, characterized in that supercritical carbon dioxide is used as the fluid. 27. The method according to any one of claims 20 to 26, characterized in that supercritical nitrous oxide is used as the fluid.   28. The method according to any one of claims 20 to 27, characterized in that that a mixture of supercritical fluids is used as the fluid. 29. The method according to any one of claims 20 to 28, characterized in that activated carbon is used as the absorbent. 30. The method according to any one of claims 20 to 29, characterized in that that as an absorbent silica gel, diatomaceous earth, molecular sieves or zeolites be used. 31. The method according to any one of claims 20 to 30, characterized in that as absorbent waste plastics, e.g. B. non-crystalline PP, Polyethylene, PES residues or organic complexing agents or a Mixture of aforementioned absorbents can be used. 32. The method according to any one of claims 20 to 31, characterized in that the supercritical fluid moderators, e.g. B. swelling agent Increase in solubility are added. 33. The method according to any one of claims 1 to 32, characterized in that the supercritical fluid after completion of the decolorization process is placed in a container for reuse. 34. The method according to any one of claims 1 to 32, characterized in that the absorbent after the decolorization process is complete thermal treatment or regenerated by rinsing with acetone.