Process for producing PVC recyclate

Abstract

For production of PVC recyclate (6) from PVC-based polymer particles (2) contaminated with phthalates (8), lead compounds, antimony compounds and / or barium compounds (9), a particle size of the polymer particles (2) within a range between 1.0 mm and 10 mm is established, and the polymer particles (2) having that particle size are treated with a solvent (5) consisting to an extent of at least 75% by weight of acetone, isopropanol and / or ethoxypropanol and including an alkaline auxiliary solvent. The treatment with the solvent (5) results in extraction of the phthalates (8), lead compounds, antimony compounds and / or barium compounds (9) over an extraction period of not more than 6.0 h and at an extraction temperature of not more 50°C from the polymer particles (2) having that particle size, leaving the PVC recyclate (6) in the extracted polymer particles (2).

Description

[0001] PROCESS FOR PRODUCING PVC RECYCLE

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The invention relates to a process for producing PVC recyclate from PVC-based plastic particles contaminated with phthalates, lead compounds, antimony compounds and / or barium compounds.

[0004] For a long time, phthalates were added to the plastics as plasticizers during the manufacture of many products made from PVC-based plastics, and lead, antimony, and / or barium compounds were added as stabilizers or for other purposes. Under the EU's REACH regulation, these additives are no longer permitted. This results in difficulties in the recycling of PVC plastics, i.e., in the production of PVC recyclate based on PVC-based plastic particles contaminated with phthalates, lead compounds, antimony compounds, and / or barium compounds. This problem will persist in the future, not least because many products imported into the EU from outside the EU will continue to contain PVC-based plastics containing additives that are actually prohibited in the EU.

[0005] STATE OF THE ART

[0006] A process for separating and recovering target polymers and their additives from a polymer-containing material having the features of the preamble of independent patent claim 1 is known from WO 2002 / 014413 A1. In this process, the polymer-containing material is comminuted and then treated with a first solvent, wherein the target polymer is dissolved together with the additives in the first solvent. The dissolved target polymer and the additives present in the same solution are mixed with a non-aqueous second solvent, which is miscible with the first solvent and in which the target polymer does not dissolve, in such a way that the target polymer is precipitated while the additives remain in dissolved form. The precipitated target polymer and at least one additive present in the liquid phase are then separated from one another.The first solvent, which dissolves the target polymer and the additives, is selected in the known process from the group of low-molecular-weight alcohols (C1-C5), cyclic ethers (e.g., tetrahydrofuran), aliphatic (e.g., acetone, methyl ethyl ketone) and cyclic ketones (e.g., cyclohexanone), basic ether mixtures (e.g., DBE), or a mixture thereof. The second solvent is a low-molecular-weight alcohol. The solvent used to dissolve the target polymer and the additives in plasticizer removal from soft PVC is tetrahydrofuran or amyl acetate-xylene. The additional solvent in this case is ethanol or, only in combination with THF, hexane. Instead of the second solvent, a solvent system consisting of water and a third solvent that forms a two-phase system with water can be used in the known process.The target polymer is then precipitated in the phase formed by the third solvent, while the additive remains dissolved in this phase. The third solvent is an aliphatic hydrocarbon, for example, n-hexane, or an aromatic hydrocarbon, for example, toluene. This known process is very time-consuming because the entire target polymer must first be dissolved in the solvent. To accelerate this dissolution, the polymer-containing material is crushed, for which a particle size of approximately 2 mm is specified. Nevertheless, the known process remains time-consuming, even if the temperature of the solvent is increased. In addition, it requires the recycling of large quantities of solvents, and the different solvents must be separated and purified from one another.In addition, when the target polymer is dissolved, insoluble fillers are separated from the target polymer, which must be added again if the target polymer is reused. Overall, the known process is therefore so complex that it has not yet been implemented on a large scale.

[0007] JP 2022 093305 A discloses a process for producing PVC recyclate. PVC-based plastic particles with a particle size of < 5 mm, which contain phthalates as plasticizers and fillers, including barium sulfate, in addition to PVC, are treated with isopropanol at 25 °C or 50 °C for 15 to 60 minutes while stirring. The liquid to solid ratio (volume / weight) is between 3 and 10. KR 2023 0142157 A discloses a process for producing PVC recyclate in which PVC waste containing lead-containing stabilizers and phthalates as plasticizers is shredded and treated at 50 °C for one hour while stirring.

[0008] OBJECT OF THE INVENTION

[0009] The invention is based on the object of demonstrating a process having the features of the preamble of independent patent claim 1, by means of which a PVC recyclate which can also be used within the EU is obtained in a cost-effective manner from PVC-based plastic particles contaminated with phthalates, lead compounds, antimony compounds and / or barium compounds.

[0010] SOLUTION

[0011] The object of the invention is achieved by a method having the features of patent claim 1. Preferred embodiments of the method according to the invention are defined in the dependent patent claims.

[0012] DESCRIPTION OF THE INVENTION

[0013] In the process according to the invention for producing PVC recyclate from plastic particles contaminated with phthalates, lead compounds, antimony compounds and / or barium compounds, a particle size of the plastic particles is set in a range between 1.0 mm and 10 mm. The plastic particles having the set particle size are treated with a solvent, wherein the solvent consists of at least 75 percent by weight of acetone, isopropanol and / or ethoxypropanol. By treating with the solvent, the phthalates, lead compounds, antimony compounds and / or barium compounds are extracted from the plastic particles having the particle size over an extraction period of not more than 6.0 hours and at an extraction temperature of not more than 50 °C, wherein the PVC recyclate remains in the extracted plastic particles.

[0014] Even if similar or even the same solvents are used in the process according to the invention as in the process known from WO 2002 / 014413 A1, unlike therein, they are not used to dissolve the target polymer. Rather, the extraction conditions are adjusted so that the PVC recyclate to be produced remains in the plastic particles treated with the solvent. These conditions include an extraction period of no more than six hours and an extraction temperature of no more than 50°C. Thus, in the process according to the invention, the interfering phthalates, lead compounds, antimony compounds and / or barium compounds are selectively extracted from the plastic particles, while not only the PVC itself but also fillers and similarly difficult-to-dissolve additives remain in the plastic particles and thus in the recyclate, which would otherwise have to be added again when the PVC is reused.

[0015] It is surprising that, using essentially the same solvents as those described in WO 2002 / 014413 A1 as solvents for dissolving not only the additives but also the target polymer, phthalates, lead compounds, antimony compounds, and / or barium compounds, which are also referred to collectively as impurities below, can be selectively dissolved from the plastic particles without dissolving large amounts of PVC. Furthermore, it is surprising that a single-stage extraction of the plastic particles with the solvent is sufficient to extract all of the impurities mentioned from the plastic particles to such an extent that the PVC recyclate remaining in the plastic particles is at least sufficiently free of these impurities to allow the recyclate to be used for the manufacture of new products within the EU, i.e., in compliance with the REACH Regulation.

[0016] The solvent contains an alkaline solvent. The alkaline solvent can be, in particular, sodium hydroxide, but also, for example, potassium hydroxide. The extraction time can be significantly shortened by dissociating hydroxide ions (OH-) in the solvent. Starting at a pH of approximately 9 or a pOH value (defined as the negative decimal logarithm of the concentration of dissociated hydroxide ions, where pH + pOH = 14 in aqueous solutions) of approximately 5, both hydrolysis of the phthalates and an improvement in the solubility of lead and antimony compounds occur. Therefore, it is advantageous to use the alkaline solvent to adjust the pH of the solvent for extraction to above 9.0, or more precisely, to a pOH value of no more than 5.0.It is even more preferred to adjust the pOH value of the solvent to no more than 3.0, even more preferably no more than 1.0, and most preferably 0, using the alkaline solubilizing agent during treatment. It should be noted that the higher the concentration of hydroxide ions (OH-) in the solution, the lower the pOH value. When all hydroxide ions (OH-) present are dissociated, a pOH value of 0 corresponds to a sodium hydroxide concentration of 4 wt.%. Typically, the solvent contains up to 5 wt.% of the alkaline solubilizing agent.

[0017] The solvent used in the extraction process according to the invention preferably consists of at least 80 percent by weight of acetone, isopropanol, or ethoxypropanol. It particularly preferably consists of at least 80 percent by weight of acetone. These solvents are easy and safe to handle, have limited environmental hazard potential, and are comparatively inexpensive.

[0018] The solvent used in the extraction of the process according to the invention can contain up to 20 percent by weight of a cosolvent, which can consist of water, ethanol, and / or other hydrocarbon compounds. The other hydrocarbon compounds can, in particular, be aliphatic hydrocarbon compounds. These preferably have six to nine carbon atoms. The cosolvent can be used to adjust the polarity of the solvent so that the relevant impurities are extracted particularly well. For example, a higher polarity of the solvent increases the extraction rate of lead and barium salts, while a lower polarity increases the extraction rate of phthalates.

[0019] The particle size of the plastic particles determines their relative surface area over which extraction takes place and the length of the diffusion paths that must be overcome during extraction. Smaller plastic particles can therefore be extracted within shorter extraction times than larger plastic particles. At the same time, however, as the size of the plastic particles decreases, the risk of PVC loss, i.e. of PVC dissolving during extraction, increases. Therefore, the particle size of the plastic particles is preferably set to at least 2.0 mm and even more preferably to at least 3.0 mm and preferably to no more than 6.0 mm and even more preferably to no more than 5.0 mm. It is particularly preferred if all plastic particles have as similar a particle size as possible, because then the further process conditions of the extraction can be precisely tailored to this particle size.It is therefore advantageous to set the particle size of the plastic particles to an accuracy of + / - 1.5 mm. The particle size is preferably set to an accuracy of + / - 1.0 mm and even more preferably to an accuracy of + / - 0.5 mm. The extraction period in the process according to the invention is preferably not more than 5.0 hours, even more preferably not more than 4.0 hours and most preferably not more than 3.0 hours. It is often about 2 hours. The extraction temperature is preferably at least 0 °C and even more preferably at least 10 °C. The maximum extraction temperature is preferably 40 °C and even more preferably 30 °C. At this comparatively low extraction temperature, the extraction takes place in a controlled manner, i.e. limited to the impurities to be removed and without any major loss of PVC.

[0020] The weight ratio of the plastic particles to the solvent during treatment, i.e. extraction, is typically no greater than 1:4 and preferably no greater than 1:9. In other words, the plastic particles make up a maximum of 20 percent by weight and preferably a maximum of 10 percent by weight of the suspension of plastic particles suspended in the solvent. At the same time, the weight ratio of the plastic particles to the solvent is typically no less than 1:99 and preferably no less than 1:60. In other words, the plastic particles make up at least one percent by weight of the suspension and preferably at least 1.7 percent by weight. In any case, the solvent is used in a significant excess to the plastic particles in order to effectively extract the contaminants.To keep the concentration difference of the contaminants between the plastic particles and the solvent as high as possible, the solvent can be stirred with the plastic particles during extraction. Alternatively or additionally, the solvent can be replaced at least once during extraction with fresh solvent of the same or a different composition, or it can be passed through a reactor in countercurrent to the plastic particles. The concentration difference is the driving force acting on the contaminants in the direction out of the plastic particles.

[0021] If the plastic particles are subjected to a pressure reduced by at least 500 hPa compared to normal pressure after treatment with the solvent, the solvent can be completely evaporated and thus completely removed from the plastic particles. The contaminants can be separated from the solvent again by filtration with activated carbon and / or by distillation at reduced pressure and / or elevated temperature. The solvent thus treated can be reused to extract the contaminants from the plastic particles.The process according to the invention is carried out in particular in such a way that the impurities are removed from the plastic particles solely by treatment with the solvent to such an extent that the PVC recyclate remaining in the plastic particles contains less than 0.1 percent by weight of phthalates, less than 0.1 percent by weight of lead compounds, less than 0.1 percent by weight of antimony compounds, and less than 0.1 percent by weight of barium compounds. This makes the PVC recyclate suitable for use in the manufacture of new PVC products within the EU in accordance with the REACH Regulation.

[0022] Specifically, the plastic particles from which the contaminants were extracted using the extraction process according to the invention can be used directly, optionally in combination with additives, as starting material for new products. However, the extracted plastic particles can also be further processed beforehand to obtain a PVC recyclate with even better properties.

[0023] Advantageous further developments of the invention emerge from the patent claims, the description and the drawings.

[0024] The advantages of features and combinations of several features mentioned in the description are merely exemplary and can be effective alternatively or cumulatively, without the advantages necessarily having to be achieved by embodiments according to the invention.

[0025] With regard to the disclosure content – ​​not the scope of protection – of the original application documents and the patent, the following applies: Further features can be found in the drawings – in particular the illustrated geometries and the relative dimensions of several components to one another, as well as their relative arrangement and operative connection. The combination of features of different embodiments of the invention or features of different patent claims is also possible, deviating from the chosen references of the patent claims, and is hereby encouraged. This also applies to features that are illustrated in separate drawings or mentioned in their description. These features can also be combined with features of different patent claims.Likewise, features listed in the patent claims may be omitted for further embodiments of the invention, but this does not apply to the independent claims of the granted patent. The features listed in the patent claims may be supplemented by further features or may be the only features contained in the subject matter of the respective patent claim.

[0026] The reference signs contained in the patent claims do not represent a limitation of the scope of the subject-matter protected by the patent claims. They serve solely to make the patent claims easier to understand.

[0027] BRIEF DESCRIPTION OF THE CHARACTERS

[0028] In the following, the invention is further explained and described with reference to a preferred embodiment shown in the figure.

[0029] Fig. 1 is a flow chart showing the process of the invention.

[0030] FIGURE DESCRIPTION

[0031] The process shown in Fig. 1 in the form of a flow chart is used to process PVC waste 1 in the form of PVC-based plastic particles 2. The PVC-based plastic particles contain fillers and other additives that can be used for recycling, but also impurities that must be removed before recycling. These impurities include in particular phthalates, which were used as plasticizers in PVC compounds, as well as lead compounds, antimony compounds and barium compounds, which were used as stabilizers for PVC plastics. In order to remove these impurities, the particle size of the plastic particles 2 is first adjusted 3 by comminution and / or sieving. The aim is to achieve as uniform a particle size as possible for all plastic particles in a preferred range of 2.0 mm to 6.0 mm and with a preferred particle size deviation of no more than + / - 1.0 mm from an average particle size.In an extraction step 4, the plastic particles 2 with the set particle size are treated with solvent 5 to extract the aforementioned impurities. The extraction step 4 is carried out in such a way that a PVC recyclate 6, which is intended for reuse, remains in the extracted plastic particles, while the impurities dissolve in the solvent 5 and can be separated from the plastic particles 2 with the solvent 5. In addition to PVC, the PVC recyclate 6 contains fillers and other additives that not only do not prevent the reuse of the PVC recyclate 6, but are actually useful for this reuse. During a treatment step 7 of the solvent 5, the phthalates 8 and the lead, antimony, and barium compounds 9 are separated from the solvent 5 by fractional distillation, which is then fed back into the extraction step 4.

[0032] In the examples documented below, the plastic particles, each adjusted to a particle size of 2 to 5 mm, were suspended in the respective solvent at a weight ratio of 1:19 and extracted with the solvent while stirring. The solvent containing the impurities was continuously removed, purified, and returned to the extraction process. After the specified extraction period at the specified extraction temperature, all of the impurities were removed from the plastic particles to less than 0.1 percent by weight, leaving a reusable PVC recyclate in the plastic particles.

[0033] Comparative Examples 1 and 2 demonstrate that by adding 1 wt.% sodium hydroxide as an alkaline solvent, resulting in a pOH value of less than 1.0 in the solvent, the extraction time can be significantly shortened by one-eighth without impairing the extraction. In Examples 3 and 4, the 4 wt.% sodium hydroxide added as a solvent results in a pOH value of 0 for the solvent.

[0034] Example 1 :

[0035] Material: PVC-w made from recycled cable, regrind 2-5 mm

[0036] Concentration: 5 wt% in solvent

[0037] Input content of impurities: 22.2 wt% phthalates, 3.2 wt% lead stearate

[0038] Solvent: 79.2 wt% ethoxypropanol, 19.8 wt% hexane

[0039] Alkaline solvent: 1 wt% sodium hydroxide

[0040] Extraction temperature: 40 °C

[0041] Extraction time: 105 min

[0042] Residual content of impurities: < 0.1 wt% phthalates, < 0.1 wt% lead stearate

[0043] Comparison example 1:

[0044] Material: PVC-w made from recycled cable, regrind 2-5 mm

[0045] Concentration: 5 wt% in solvent Input content of impurities: 22.2 wt% phthalates, 3.2 wt% lead stearate

[0046] Solvent: 80 wt% ethoxypropanol, 20 wt% hexane

[0047] Extraction temperature: 40 °C

[0048] Extraction time: 120 min

[0049] Residual content of impurities: < 0.1 wt% phthalates, < 0.1 wt% lead stearate

[0050] Example 2:

[0051] Material: PVC-w from tarpaulins, defibrated, ground material 2-5 mm

[0052] Concentration: 5 wt% in solvent

[0053] Input content of impurities: 32.1 wt% phthalates, 1.8 wt% lead stearate

[0054] 0.9 wt% lead oxide, 1.9 wt% antimony oxide

[0055] Solvent: 89.1 wt% acetone, 9.9 wt% ethanol

[0056] Alkaline solvent: 1 wt% sodium hydroxide

[0057] Extraction temperature: 30 °C

[0058] Extraction time: 135 min

[0059] Residual content of impurities: < 0.1 wt% phthalates, < 0.1 wt% lead stearate

[0060] < 0.1 wt% lead oxide, < 0.1 wt% antimony oxide

[0061] Comparison example 2:

[0062] Material: PVC-w from tarpaulins, defibrated, ground material 2-5 mm

[0063] Concentration: 5 wt% in solvent

[0064] Input content of impurities: 32.1 wt% phthalates, 1.8 wt% lead stearate

[0065] 0.9 wt% lead oxide, 1.9 wt% antimony oxide

[0066] Solvent: 90 wt% acetone, 10 wt% ethanol

[0067] Extraction temperature: 30 °C

[0068] Extraction time: 150 min

[0069] Residual content of impurities: < 0.1 wt% phthalates, < 0.1 wt% lead stearate

[0070] < 0.1 wt% lead oxide, < 0.1 wt% antimony oxide

[0071] Example 3:

[0072] Material: PVC-w from floor covering, ground material 2-5 mm

[0073] Concentration: 5 wt% in solvent

[0074] Input content of impurities: 36.2 wt% phthalates, 1.9 wt% lead stearate

[0075] 2.6 wt% antimony oxide Solvent: 96 wt% isopropanol

[0076] Alkaline solvent: 4 wt% sodium hydroxide

[0077] Extraction temperature: 20 °C

[0078] Extraction time: 180 min Residual content of impurities: < 0.1 wt.% phthalates, < 0.1 wt.% lead stearate,

[0079] < 0.1 wt% antimony oxide

[0080] Example 4:

[0081] Material: PVC-w made of hoses with PET reinforcement fabric,

[0082] Milling material 2-5 mm Concentration: 5 wt.% in solvent

[0083] Input content of impurities: 48.0 wt% phthalates, 0.6 wt% lead stearate

[0084] Solvent: 96 wt% ethoxypropanol

[0085] Alkaline solvent: 4 wt% sodium hydroxide

[0086] Extraction temperature: 50 °C Extraction time: 150 min

[0087] Residual content of impurities: < 0.1 wt% phthalates, < 0.1 wt% lead stearate

[0088] LIST OF REFERENCE SYMBOLS PVC waste Plastic particles Adjustment Extraction Solvent PVC recyclate Processing Phthalates Lead, antimony and barium compounds

Claims

PATENT CLAIMS 1. A process for producing PVC recyclate (6) from PVC-based plastic particles (2) contaminated with phthalates (8), lead compounds, antimony compounds and / or barium compounds (9), wherein a particle size of the plastic particles (2) is set in a range between 1.0 mm and 10 mm, wherein the plastic particles (2) having the set particle size are treated with a solvent (5), wherein the solvent (5) contains at least 75 wt.-% of acetone, isopropanol and / or ethoxypropanol and has an alkaline solvent, and wherein by treatment with the solvent (5) the phthalates (8), lead compounds, antimony compounds and / or barium compounds (9) are extracted from the plastic particles (2) having the particle size over an extraction period of not more than 6.0 h and at an extraction temperature of not more than 50°C, wherein the PVC recyclate (6) remains in the extracted plastic particles (2).

2. The method according to claim 1, wherein the solvent (5) consists of at least 80% by weight of acetone, isopropanol or ethoxypropanol and preferably of acetone.

3. A process according to any one of the preceding claims, wherein the solvent (5) comprises 0 to 20 wt.% of a cosolvent consisting of water, ethanol and / or other hydrocarbon compounds.

4. The process according to claim 3, wherein the other hydrocarbon compounds are aliphatic hydrocarbon compounds and preferably have 6 to 9 carbon atoms.

5. The method according to claim 3 or 4, wherein the solvent (5) comprises at least 1.0 wt.% and preferably at least 5 wt.% of the cosolvent.

6. A process according to any one of the preceding claims, wherein the alkaline dissolving agent is sodium hydroxide.

7. The method according to any one of the preceding claims, wherein the alkaline dissolving agent is used during the treatment to adjust the pH of the solvent (5) to more than 9.

0.

8. The method according to any one of the preceding claims, wherein the alkaline dissolving agent is used during the treatment to adjust the pOH value of the solvent (5) to not more than 5.

0.

9. The method according to claim 8, wherein the alkaline dissolving agent is used during the treatment to adjust the pOH value of the solvent (5) to not more than 3.0, preferably to not more than 1.0 and most preferably to 0.

10. The method according to any one of the preceding claims, wherein the solvent (5) comprises up to 5% by weight of the alkaline dissolving agent.

11. Method according to one of the preceding claims, wherein the particle size is adjusted to at least 2.0 mm and preferably to at least 3.0 mm and / or to not more than 6.0 mm and preferably to not more than 5.0 mm and / or wherein the particle size is adjusted to a maximum of + / - 1.5 mm, preferably to a maximum of + / - 1.0 mm and even more preferably to a maximum of + / - 0.5 mm.

12. A process according to any one of the preceding claims, wherein the extraction period is not more than 5.0 h, preferably not more than 4.0 h and most preferably not more than 3.0 h.

13. Process according to one of the preceding claims, wherein the extraction temperature is at least 0°C and preferably at least 10°C and / or at most 40°C and preferably at most 30°C.

14. Method according to one of the preceding claims, wherein the weight ratio of the plastic particles (2) and the solvent (5) during the treatment is not greater than 1:4 and preferably not greater than 1:9 and / or not less than 1:99 and preferably not less than 1:

60.

15. Method according to one of the preceding claims, wherein during the treatment the solvent (5) is stirred with the plastic particles (2) and / or the solvent (5) is passed in countercurrent to the plastic particles (2).

16. Method according to one of the preceding claims, wherein the plastic particles (2) are subjected after treatment to a pressure reduced by at least 500 hPa compared to normal pressure in order to completely remove the solvent (5).

17. Method according to one of the preceding claims, wherein the solvent (5) is processed after the treatment in order to remove contained phthalates (8), antimony compounds and / or barium compounds (9) therefrom and is then used again for the treatment.

18. A method according to any one of the preceding claims, wherein the phthalates (8), lead compounds, antimony compounds and / or barium compounds (9) are separated again from the solvent (5) by: Filtration with activated carbon and / or Distillation at reduced pressure and / or elevated temperature.

19. Method according to one of the preceding claims, wherein the phthalates (8), lead compounds, antimony compounds and / or barium compounds (9) are removed from the plastic particles (2) exclusively by treatment with the solvent (5), wherein the PVC recyclate (6) is obtained with less than 0.1 wt.% phthalates (8), less than 0.1 wt.% lead compounds, less than 0.1 wt.% antimony compounds and less than 0.1 wt.% barium compounds (9).

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