Process for producing pvc recyclate

Abstract

For producing a PVC recyclate (6) from PVC-based plastic particles (2) contaminated with phthalates (8), lead compounds, antimony compounds and / or barium compounds (9), the particle size of the plastic particles (2) is adjusted to a range of 1.0 mm to 10 mm and the plastic particles (2) having this particle size are treated with a solvent (5) consisting of at least 75 % by weight of acetone, isopropyl alcohol and / or ethoxypropanol and containing a basic solubilizing aid. By treating with the solvent (5), phthalates (8), lead compounds, antimony compounds and / or barium compounds (9) are extracted from the plastic particles (2) having the stated particle size in an extraction time of not more than 6.0 hours and an extraction temperature of not more than 50 °C, wherein the PVC recyclate (6) remains in the plastic particles (2) after extraction.

Description

[0001] Technical Field of the Invention This invention relates to a method for producing recycled PVC material from PVC-based plastic pellets contaminated with phthalates, lead compounds, antimony compounds, and / or barium compounds.

[0002] Phthalates have long been added to PVC-based plastics as plasticizers in the production of many products, along with lead, antimony, and / or barium compounds as stabilizers or for other purposes. Under the EU REACH regulation, these additives are no longer permitted. This has led to difficulties in the recycling of PVC plastics, specifically in the production of recycled PVC materials based on PVC-based plastic pellets contaminated with phthalates, lead, antimony, and / or barium compounds. This problem will likely persist, at least because many products imported from outside the EU will continue to contain PVC-based plastics containing additives that are effectively prohibited in the EU.

[0003] Existing technology A method for separating and recovering a target polymer and its additives from a polymer-containing material is known from WO 2002 / 014413 A1, the method having the features described in the preamble of independent claim 1. In this method, the polymer-containing material is pulverized and subsequently treated with a first solvent, wherein the target polymer and the additives are dissolved together in the first solvent. The dissolved target polymer and the additives present in the same solution are mixed with a second non-aqueous solvent such that the target polymer precipitates while the additives remain in dissolved form, the second non-aqueous solvent being miscible with the first solvent and the target polymer being insoluble therein. The precipitated target polymer and at least one additive present in the liquid phase are then separated from each other. In this known method, the first solvent for dissolving the target polymer and the additives is selected from low molecular weight alcohols (C1-C5), cyclic ethers (e.g., tetrahydrofuran), aliphatic ketones (e.g., acetone, methyl ethyl ketone), and cyclic ketones (e.g., cyclohexanone), basic ether mixtures (e.g., DBE), or mixtures thereof. The second solvent is a low molecular weight alcohol. When separating plasticizers from flexible PVC, the solvent used to dissolve the target polymer and the additives is tetrahydrofuran or amyl acetate / xylene. In this case, the additional solvent is ethanol, or (only when used in conjunction with THF) hexane. The known method can replace the second solvent with a solvent system comprising water and a third solvent forming a two-phase system with water. The target polymer is then precipitated in the phase formed by the third solvent, while the additive remains dissolved in that phase. The third solvent is an aliphatic hydrocarbon, such as n-hexane, or an aromatic hydrocarbon, such as toluene. This known method 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 pulverized, with a particle size of approximately 2 mm specified for this purpose. However, even when the solvent temperature is increased, the known method remains time-consuming. Furthermore, it requires the circulation of large quantities of solvent, and different solvents must be separated and purified from each other. Additionally, during the dissolution of the target polymer, insoluble filler separates from the target polymer, and this filler must be reintroduced when the target polymer is reused. In summary, the known method is therefore so complex that it has not yet been implemented on an industrial scale.

[0004] JP 2022 093305 A discloses a method for producing recycled PVC. While stirring, PVC-based plastic granules with a particle size <5 mm are treated with isopropanol at 25°C or 50°C for 15 to 60 minutes. These PVC-based plastic granules contain phthalates as plasticizers and fillers in addition to PVC, particularly barium sulfate. The liquid-to-solid ratio (volume / weight) is 3 to 10.

[0005] KR 2023 0142157 A discloses a method for producing recycled PVC material, wherein PVC waste containing lead stabilizers and phthalates as plasticizers is crushed and treated at 50°C for 1 hour while being stirred.

[0006] The purpose of this invention The object of the present invention is to provide a method having the features of the preamble of independent claim 1, by which PVC recycled material, which can also be used in the EU, is obtained in a cost-effective manner from PVC-based plastic pellets contaminated with phthalates, lead compounds, antimony compounds and / or barium compounds.

[0007] Solution The object of the present invention is achieved by a method having the features of claim 1. Preferred embodiments of the method according to the invention are defined in the dependent claims.

[0008] Description of the present invention In the method according to the invention for producing recycled PVC from plastic particles contaminated with phthalates, lead compounds, antimony compounds, and / or barium compounds, the particle size of the plastic particles is adjusted to a range between 1.0 mm and 10 mm. The plastic particles having the adjusted particle size are treated with a solvent, wherein the solvent consists of at least 75% by weight of acetone, isopropanol, and / or ethoxypropanol. By solvent treatment, phthalates, lead compounds, antimony compounds, and / or barium compounds are extracted from the plastic particles having said particle size at an extraction time not exceeding 6.0 hours and an extraction temperature not exceeding 50°C, wherein the recycled PVC remains in the extracted plastic particles.

[0009] Although the method according to the invention uses solvents similar to or even the same as those used in the methods known in WO 2002 / 014413 A1, unlike that method, these solvents are not used to dissolve the target polymer. Instead, the extraction conditions are adjusted such that the resulting recycled PVC material remains in the solvent-treated plastic particles. These conditions include an extraction time of up to 6 hours and an extraction temperature of up to 50°C. In this way, in the method according to the invention, 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 similar slightly soluble additives remain in the plastic particles, and therefore in the recycled material, which would otherwise have to be added back when the PVC is reused.

[0010] Surprisingly, using solvents essentially the same as those described in WO 2002 / 014413 A1—in which the solvent is used not only to dissolve the additives but also the target polymer—phthalates, lead compounds, antimony compounds, and / or barium compounds (collectively referred to as contaminants below) can be selectively dissolved from plastic pellets without dissolving large amounts of PVC. Furthermore, surprisingly, single-stage solvent extraction of the plastic pellets is sufficient to extract all of the aforementioned contaminants, making the PVC recyclable material remaining in the pellets at least sufficiently free of these contaminants for use in the production of new products, compared to recyclable material that can also be used within the EU (i.e., compliant with REACH regulations).

[0011] The solvent includes a basic solubilizing agent. The basic solubilizing agent can be, in particular, sodium hydroxide, but can also be, for example, potassium hydroxide. The extraction time can be significantly shortened by the dissociation of hydroxide ions (OH-) in the solvent. Starting from a pH of approximately 9 or from a corresponding pOH value of approximately 5 (pOH is defined as the negative common logarithm of the concentration of dissociated hydroxide ions, where pH + pOH = 14 in aqueous solution), the hydrolysis of phthalates and the improvement of the solubility of lead and antimony compounds occur. Therefore, it is advantageous to adjust the pH of the solvent used for extraction to be greater than 9.0, or more precisely, not greater than 5.0, by using a basic solubilizing agent. More preferably, the pOH value of the solvent is adjusted during treatment to not more than 3.0, even more preferably to not more than 1.0, and most preferably to 0. It should be taken into consideration that the higher the concentration of hydroxide ions (OH-) in the solution, the lower the pOH value. A pOH value of 0 corresponds to a sodium hydroxide concentration of 4% by weight when all present hydroxide ions (OH-) are dissociated. Typically, the solvent contains up to 5% by weight of basic solubilizing agent.

[0012] Preferably, the solvent used in the extraction according to the method of the invention consists of at least 80% by weight acetone, isopropanol, or ethoxypropanol. Particularly preferably, it consists of at least 80% by weight acetone. The above solvents are easy and safe to manage, and at the same time have limited environmental hazard potential and are relatively inexpensive.

[0013] The solvent used in the extraction according to the method of the invention may contain up to 20% by weight of a co-solvent, which may consist of water, ethanol, and / or other hydrocarbon compounds. Other hydrocarbon compounds may be, in particular, aliphatic hydrocarbon compounds. Preferably, these contain six to nine carbon atoms. By means of a co-solvent, the polarity of the solvent can be adjusted, making the extraction of relevant contaminants particularly efficient. For example, higher solvent polarity increases the extraction rate of lead and barium salts, while lower polarity increases the extraction rate of phthalates.

[0014] The particle size adjusted for the plastic particles determines their relative surface area (on which extraction occurs) and the length of the diffusion path to be overcome during extraction. Therefore, smaller plastic particles can be extracted in a shorter time compared to larger ones. However, the risk of PVC loss, i.e., PVC dissolution during extraction, increases with decreasing particle size. Therefore, it is preferable to adjust the particle size to at least 2.0 mm, more preferably at least 3.0 mm, more preferably no more than 6.0 mm, and even more preferably no more than 5.0 mm. Particularly preferred is that all plastic particles have the most uniform particle size possible, as the further process conditions for extraction can then be precisely matched to this particle size. Therefore, it is advantageous to adjust the particle size with a maximum tolerance of + / - 1.5 mm. Preferably, the particle size is adjusted with a maximum tolerance of + / - 1.0 mm, and even more preferably with a maximum tolerance of + / - 0.5 mm.

[0015] In the method according to the invention, the extraction time is preferably no more than 5.0 hours, more preferably no more than 4.0 hours, and most preferably no more than 3.0 hours. Typically, it is about 2 hours. The extraction temperature is preferably at least 0°C, more preferably at least 10°C. Preferably, the extraction temperature is at most 40°C, more preferably at most 30°C. At this relatively low extraction temperature, the extraction is carried out in a controlled manner, i.e., limited to the contaminants to be removed and without significant loss of PVC.

[0016] During the treatment, i.e., during extraction, the weight ratio of plastic particles to solvent is typically no greater than 1:4, preferably no greater than 1:9. In other words, in the suspension of plastic particles in the solvent, the plastic particles account for at most 20% by weight, preferably at most 10% by weight. Simultaneously, the weight ratio of plastic particles to solvent is typically no less than 1:99, preferably no less than 1:60. In other words, the plastic particles account for at least 1% by weight of the suspension, preferably at least 1.7% by weight. In any case, a significant excess of solvent relative to the plastic particles is used to effectively extract the contaminant. To maintain the highest possible concentration gradient of the contaminant between the plastic particles and the solvent, the solvent can be stirred together with the plastic particles during extraction. As an alternative or supplementary method, the solvent can be replaced at least once during extraction, using a fresh solvent of the same or different composition, or the solvent can be passed through the reactor countercurrently to the plastic particles. The concentration gradient constitutes the driving force acting on the contaminant in the direction away from the plastic particles.

[0017] If, after solvent treatment, the plastic particles are subjected to a pressure reduction of at least 500 hPa relative to atmospheric pressure, the solvent can be completely evaporated and thus completely removed from the plastic particles. Contaminants can be separated again from the solvent by filtration with activated carbon and / or by distillation under reduced pressure and / or increased temperature. The solvent, retreated in this way, can then be reused to extract contaminants from the plastic particles.

[0018] The method according to the invention is carried out in a manner in which contaminants are removed from plastic particles solely by solvent treatment to such an extent that the PVC recycled material remaining in the plastic particles contains less than 0.1% by weight of phthalates, less than 0.1% by weight of lead compounds, less than 0.1% by weight of antimony compounds, and less than 0.1% by weight of barium compounds. Therefore, the PVC recycled material can be used in the EU according to REACH regulations for the production of new products made from PVC.

[0019] Specifically, plastic particles from which contaminants have been extracted by extraction according to the invention can be used directly (optionally combined with aggregates) as starting materials for new products. However, the extracted plastic particles can also be further pre-treated to obtain recycled PVC with even more improved properties.

[0020] Further advantageous improvements to the invention will be apparent from the patent claims, specification, and drawings.

[0021] The advantages of the features and combinations of features mentioned in the specification are merely exemplary and may take effect alternatively or cumulatively, and these advantages need not be realized by means of embodiments according to the invention.

[0022] Regarding the disclosure (but not the scope of protection) of the original application documents and patents, the following applies: Other features are apparent from the accompanying drawings, particularly from the geometry shown and the relative dimensions of the various components relative to each other, and from their relative arrangement and operational connections. Features of different embodiments of the invention or combinations of features from different patent claims may also deviate from the selected dependency of the patent claims, and are hereby indicated. This also applies to such features shown in separate drawings or mentioned in their description. These features may also be combined with features from different patent claims. Similarly, features listed in patent claims may be omitted for other embodiments of the invention; however, these features do not apply to the independent claims of granted patents.

[0023] The features specified in a patent claim may be supplemented by further features, or may constitute the unique feature of the subject matter of the corresponding patent claim.

[0024] The reference numerals included in the patent claims do not constitute a limitation on the scope of the subject matter protected by the patent claims. They are used solely for the purpose of making the patent claims easier to understand.

[0025] Brief description of the attached figures The invention will now be explained and described in more detail with reference to the preferred embodiments shown in the figures.

[0026] Figure 1 This is a flowchart illustrating the sequence of the method according to the present invention.

[0027] Description of the attached figures Figure 1 The method shown in the flowchart is used to process PVC waste 1 in the form of PVC-based plastic pellets 2. The PVC-based plastic pellets contain fillers and other additives that can be recycled, and also contain contaminants that must be removed before recycling. These contaminants include, in particular, phthalates used as plasticizers in PVC compounds, and lead, antimony, and barium compounds used as stabilizers in PVC plastics. To remove these contaminants, the particle size 3 of the plastic pellets 2 is first adjusted by crushing and / or sieving. The aim is to make all plastic pellets as uniform as possible in the preferred range of 2.0 mm to 6.0 mm, and the preferred deviation of the particle size from the average particle size is no more than + / - 1.0 mm. In extraction 4, the plastic pellets 2 with the adjusted particle size are treated with solvent 5 to extract the aforementioned contaminants. Extraction 4 is carried out in such a way that the PVC recycled material 6 intended for reuse remains in the extracted plastic pellets, while the contaminants are dissolved in solvent 5 and can be separated from the plastic pellets 2 together with solvent 5. The PVC recycled material 6 contains fillers and other additives in addition to PVC, which not only do not hinder the reuse of the PVC recycled material 6, but are even useful for such reuse. During the reprocessing 7 of solvent 5, phthalates 8 and lead, antimony and barium compounds 9 are separated from solvent 5 by fractionation, after which the solvent is returned to extraction 4.

[0028] In the embodiments described below, plastic particles, each adjusted to a particle size of 2 to 5 mm, were suspended in their respective solvents at a weight ratio of 1:19 and extracted with the solvent while stirring. The contaminant-laden solvent was continuously discharged, purified, and returned to the extraction. After a specified extraction time at a specified extraction temperature, all contaminants had been removed from the plastic particles to less than 0.1% by weight, leaving reusable recycled PVC material in the plastic particles.

[0029] Comparative Examples 1 and 2, related to Examples 1 and 2, show that by adding 1% by weight of sodium hydroxide as an alkaline solubilizer, a pOH value of less than 1.0 can be established in the solvent, and the extraction time can be significantly reduced by one-eighth without deteriorating the extraction. In Examples 3 and 4, the addition of 4% by weight of sodium hydroxide as a solubilizer resulted in a pOH value of 0 in the solvent.

[0030] Example 1: Materials: PVC waste from cable recycling, abrasive, particle size 2-5mm Concentration: 5% by weight in solvent Initial contaminant content: 22.2 wt% phthalates, 3.2 wt% lead stearate Solvents: 79.2 wt% ethoxypropanol, 19.8 wt% hexane Alkaline solubilizing agent: 1% sodium hydroxide Extraction temperature: 40℃ Extraction time: 105 minutes Residual contaminant content: <0.1% by weight phthalates, <0.1% by weight lead stearate Comparative Example 1: Materials: PVC waste from cable recycling, abrasive, particle size 2-5mm Concentration: 5% by weight in solvent Initial contaminant content: 22.2 wt% phthalates, 3.2 wt% lead stearate Solvents: 80% wt% ethoxypropanol, 20% wt% hexane Extraction temperature: 40℃ Extraction time: 120 minutes Residual contaminant content: <0.1% by weight phthalates, <0.1% by weight lead stearate Example 2: Materials: Defiberized PVC waste from waterproof tarpaulins, abrasive, 2-5mm particle size. Concentration: 5% by weight in solvent Initial contaminant content: 32.1 wt% phthalates, 1.8 wt% lead stearate 0.9 wt% lead oxide, 1.9 wt% antimony oxide Solvents: 89.1% wt acetone, 9.9% wt ethanol Alkaline solubilizing agent: 1% sodium hydroxide Extraction temperature: 30℃ Extraction time: 135 minutes Residual contaminant content: <0.1% by weight phthalates, <0.1% by weight lead stearate <0.1% by weight lead oxide, <0.1% by weight antimony oxide Comparative Example 2: Materials: Defiberized PVC waste from waterproof tarpaulins, abrasive, 2-5mm particle size. Concentration: 5% by weight in solvent Initial contaminant content: 32.1 wt% phthalates, 1.8 wt% lead stearate 0.9 wt% lead oxide, 1.9 wt% antimony oxide Solvents: 90% wt acetone, 10% wt ethanol Extraction temperature: 30℃ Extraction time: 150 minutes Residual contaminant content: <0.1% by weight phthalates, <0.1% by weight lead stearate <0.1% by weight lead oxide, <0.1% by weight antimony oxide Example 3: Materials: PVC waste from floor coverings, abrasive, 2-5mm grit. Concentration: 5% by weight in solvent Initial contaminant content: 36.2 wt% phthalates, 1.9 wt% lead stearate 2.6% by weight antimony oxide Solvent: 96% by weight isopropanol Alkaline solubilizing agent: 4% sodium hydroxide by weight Extraction temperature: 20℃ Extraction time: 180 minutes Residual contaminant content: <0.1% by weight phthalates, <0.1% by weight lead stearate <0.1% by weight of antimony oxide Example 4: Materials: PVC waste from hoses with PET-reinforced fabric, abrasive, 2-5mm grit. Concentration: 5% by weight in solvent Initial contaminant content: 48.0 wt% phthalates, 0.6 wt% lead stearate Solvent: 96% wt% ethoxypropanol Alkaline solubilizing agent: 4% sodium hydroxide by weight Extraction temperature: 50℃ Extraction time: 150 minutes Residual contaminant content: <0.1% by weight phthalates, <0.1% by weight lead stearate Figure Labels

Claims

1. A method for producing recycled PVC material (6) from PVC-based plastic pellets (2) contaminated with phthalates (8), lead compounds, antimony compounds and / or barium compounds (9), - The particle size of the plastic granules (2) is adjusted to the range of 1.0 mm to 10 mm. - Plastic particles (2) having an adjusted particle size are treated with a solvent (5) comprising at least 75% by weight of acetone, isopropanol and / or ethoxypropanol and containing an alkaline solubilizing agent, and wherein phthalates (8), lead compounds, antimony compounds and / or barium compounds (9) are extracted from the plastic particles (2) having the particle size by treatment with the solvent (5) for an extraction time not exceeding 6.0 h and an extraction temperature not exceeding 50 °C, wherein recycled PVC material (6) remains in the extracted plastic particles (2).

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

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

4. The method of claim 3, wherein the other hydrocarbon compound is an aliphatic hydrocarbon compound and preferably contains 6-9 carbon atoms.

5. The method of claim 3 or 4, wherein the solvent (5) comprises at least 1.0% by weight and preferably at least 5% by weight of a co-solvent.

6. The method according to any one of the preceding claims, wherein the alkaline solubilizing agent is sodium hydroxide.

7. The method according to any one of the preceding claims, wherein, With the aid of the alkaline solubilizing agent, the pH of the solvent (5) is adjusted to be greater than 9.0 during the treatment.

8. The method according to any one of the preceding claims, wherein, With the aid of the alkaline solubilizing agent, the pOH value of the solvent (5) is adjusted to be no greater than 5.0 during the treatment.

9. The method according to claim 8, wherein, With the aid of the alkaline solubilizing agent, the pOH value of the solvent (5) is adjusted to no more than 3.0, preferably no more than 1.0, and most preferably 0 during the treatment.

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

11. The method according to any one of the preceding claims, - Wherein the particle size is adjusted to at least 2.0 mm, preferably at least 3.0 mm and / or no more than 6.0 mm, preferably no more than 5.0 mm, and / or - The particle size is adjusted with a maximum tolerance of + / -1.5 mm, preferably + / -1.0 mm, or even more preferably + / -0.5 mm.

12. The method according to any one of the preceding claims, wherein the extraction time does not exceed 5.0 h, preferably not more than 4.0 h, and most preferably not more than 3.0 h.

13. The method according to any 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. The method according to any one of the preceding claims, wherein the weight ratio of the plastic particles (2) to 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. The method according to any one of the preceding claims, wherein, During the process, the solvent (5) is stirred together with the plastic particles (2) and / or the solvent (5) is directed in a countercurrent manner to the plastic particles (2).

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

17. The method according to any one of the preceding claims, wherein after the treatment, the solvent (5) is reprocessed to remove the phthalates (8), antimony compounds and / or barium compounds (9) contained therein, before being used in the treatment.

18. The method according to any one of the preceding claims, wherein the phthalate (8), lead compound, antimony compound and / or barium compound (9) are separated from the solvent (5) again by means of: - Filter with activated carbon and / or - Distillation under reduced pressure and / or increased temperature.

19. The method according to any one of the preceding claims, wherein the phthalate (8), lead compound, antimony compound and / or barium compound (9) are removed from the plastic particles (2) by treatment with the solvent (5) alone, wherein the PVC recycled material (6) is obtained having less than 0.1% by weight of phthalate (8), less than 0.1% by weight of lead compound, less than 0.1% by weight of antimony compound and less than 0.1% by weight of barium compound (9).

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