A phase separation type organic solvent and a treatment process of marine source polyvinyl chloride foam waste

Abstract

This application relates to the field of marine-source polyvinyl chloride (PVC) waste treatment technology, specifically disclosing a phase-separation type organic solvent and a treatment process for marine-source PVC foam waste. The phase-separation type organic solvent includes a dissolving phase, a desalting phase, and a phase stabilizer. The dissolving phase includes limonene and p-methoxycyclohexanone. The desalting phase is a saturated diol. The phase stabilizer is tributyl phosphate. The dissolving phase is responsible for dissolving the PVC foam, the desalting phase is responsible for adsorbing the water and salt carried in the foam, and the phase stabilizer ensures a clear, non-emulsifying interface between the two phases. The three phases work synergistically to achieve simultaneous dissolution, desalination, and phase separation, and the regenerated PVC has extremely low salt content, eliminating the need for a water washing desalination step, thus reducing the generation and discharge of high-salt wastewater.

Description

Technical Field

[0001] This application relates to the field of marine-source polyvinyl chloride (PVC) waste treatment technology, specifically disclosing a phase-separated organic solvent and a treatment process for marine-source PVC foam waste. Background Technology

[0002] Polyvinyl chloride (PVC) foam buoys and floats, which are widely used in marine aquaculture and shipping operations, are partially abandoned and float on the sea surface due to their closed-cell foam structure, while others sink to the seabed or remain suspended in the water. They become solid wastes that are difficult to degrade in the marine environment and pose a continuous threat to the marine ecosystem.

[0003] Several technical routes for solvent-based recycling of polyvinyl chloride (PVC) waste have been disclosed: First, a two-step dissolution-precipitation method, using solvents such as methyl ethyl ketone (MEK) to dissolve PVC under pressure at 70-140°C, followed by precipitation with steam or alcohols; the solvent can then be recycled. Second, a high-boiling-point single-phase solvent method, using dimethyl sulfoxide (DMSO), N-methylpyrrolidone (N-methylpyrrolidone), etc., to dissolve PVC under high-boiling-point conditions, followed by filtration and the addition of water or alcohols to precipitate the PVC. Third, a supercritical anti-solvent method, relying on supercritical fluids to induce PVC precipitation and regeneration.

[0004] The above methods all use a single organic phase for dissolution. The solvent has poor tolerance to moisture and salt. When processing marine-sourced PVC foam materials with high water and salt content, the following problems are likely to occur: ① The solvent absorbs water and emulsifies, resulting in a sharp drop in dissolution efficiency; ② Salt accumulates and suspends in the organic phase, leading to increased solvent loss; ③ The recycled material has excessive salt content, requiring multi-stage water washing to remove salt and generating high-salt wastewater. Summary of the Invention

[0005] In response to the problems in relevant marine-source PVC foam waste dissolution and recycling technologies, such as solvent pollution and high losses due to water-salt coexistence, excessive salt content in recycled materials, high-salt wastewater generated by multi-stage water washing and desalination, and high treatment costs, this application constructs a phase-separated organic solvent and marine-source PVC foam waste treatment process to achieve marine-source PVC foam waste regeneration without the generation of high-salt wastewater, improve the purity of recycled materials and solvent recovery rate, and adapt to the treatment needs of coastal and offshore platforms.

[0006] In the first aspect, this application proposes a phase-separated organic solvent and adopts the following technical solution.

[0007] A phase-separated organic solvent includes a dissolving phase, a desalting phase, and a phase stabilizer; the dissolving phase includes limonene and p-methoxycyclohexanone; the desalting phase is a saturated diol; and the phase stabilizer is tributyl phosphate.

[0008] By adopting the above technical solution, the dissolving phase is responsible for dissolving the polyvinyl chloride foam, the desalination phase is responsible for adsorbing the moisture and salt carried in the foam, and the phase stabilizer makes the interface between the two phases clear and non-emulsified. The three work together to achieve simultaneous dissolution, desalination, and phase separation, and the recycled polyvinyl chloride has a very low salt content, eliminating the need for a water washing desalination step and reducing the generation and discharge of high-salt wastewater.

[0009] A preferred embodiment of this phase-separated organic solvent is that the desalting phase is ethylene glycol, diethylene glycol, or triethylene glycol.

[0010] By adopting the above technical solutions, these saturated diols are characterized by high polarity, complete miscibility with water, and good solubility for inorganic salts. They are also basically immiscible with the dissolved phase, which can effectively adsorb water and salt in marine foam, thus making the two phases stably separate.

[0011] A preferred embodiment of this phase-separated organic solvent is that the volume ratio of the dissolving phase, the desalting phase, and the phase stabilizer is 100:(80~120):(0.5~1.5).

[0012] By adopting the above technical solution, the volume ratio of each component in the solvent system results in better phase separation and achieves a residual salt content of ≤0.1wt% in the recycled material.

[0013] A preferred embodiment of this phase-separated organic solvent is that the volume ratio of limonene to p-methoxycyclohexanone is (60~80):(20~40).

[0014] By adopting the above technical solution, the polarity complementarity between the strong nonpolar solvent limonene and the strong polar solvent p-methoxycyclohexanone is beneficial to the separation of the desalted phase. On the other hand, limonene permeates the polyvinyl chloride (PVC) to cause the PVC to swell, and p-methoxycyclohexanone dissolves the swollen PVC. Limonene and p-methoxycyclohexanone constitute a composite organic phase with high efficiency in dissolving PVC.

[0015] Secondly, this application proposes a treatment process for marine-sourced polyvinyl chloride foam waste, and adopts the following technical solution.

[0016] A process for treating marine-source polyvinyl chloride (PVC) foam waste, employing the aforementioned phase-separation type organic solvent; the process for treating marine-source PVC foam waste includes: S1, add marine-sourced polyvinyl chloride foam waste to the phase-separation type organic solvent, heat to dissolve, let stand to separate layers, collect the dissolved phase layer and the desalination phase layer respectively, and filter to remove impurities; S2, the dissolved phase layer is evaporated, and the evaporated dissolved phase is recycled to obtain polyvinyl chloride containing the stabilizer; S3, the desalination phase in the desalination phase layer is separated and recycled.

[0017] By employing the above technical solution, S1 involves heating to dissolve polyvinyl chloride (PVC), followed by static stratification to separate the PVC solution, desalination solution, and solid impurities into three phases. S2 involves evaporation to recover the dissolved solvent for recycling, simultaneously yielding recycled PVC containing a phase stabilizer. S3 involves treating the desalination phase to achieve solvent recycling. The entire process generates no high-salt wastewater, and the solvent recovery rate is ≥92%. It should be noted that steps S2 and S3 can be performed simultaneously or sequentially.

[0018] A preferred embodiment of the treatment process for marine-sourced polyvinyl chloride foam waste is that the ratio of the mass of the marine-sourced polyvinyl chloride foam waste to the volume of the phase-separated organic solvent is 1 kg: (8~12) L.

[0019] By adopting the above technical solution, the solid-liquid ratio of foam waste to organic solvent is optimized. Within this ratio range, both the complete dissolution of polyvinyl chloride and the treatment efficiency and economy can be guaranteed.

[0020] A preferred embodiment of the treatment process for marine-sourced polyvinyl chloride foam waste is that the heating temperature in step S1 is 50~70℃, and stirring is performed during heating.

[0021] By adopting the above technical solution, the heating and dissolving conditions are limited to 50~70℃ accompanied by stirring. This temperature can accelerate the movement of PVC molecular chains and solvent penetration, shortening the dissolving time to 10~30 minutes, without causing solvent boiling or PVC thermal degradation. Stirring ensures uniform mixing of materials, avoiding localized excessively high or low concentrations.

[0022] A preferred embodiment of the treatment process for marine-sourced polyvinyl chloride foam waste is as follows: the treatment method in step S2 is as follows: the dissolved phase layer is introduced into a thin-film evaporator and subjected to vacuum distillation at 1kPa~5kPa and 120~160℃. The solvent is first evaporated and then condensed for recovery. The condensed solvent is recycled as the dissolved phase. The unevaporated residue is a mixture of the stabilizer and polyvinyl chloride. The mixture is then regenerated to obtain recycled polyvinyl chloride.

[0023] By employing the above technical solution, a thin-film evaporator is used to treat the dissolved phase layer under reduced pressure. The thin-film evaporator forms a thin layer of material on the heating surface, with a residence time ranging from several seconds to tens of seconds. Combined with high vacuum, this allows for rapid solvent evaporation at temperatures below the boiling point, preventing thermal degradation of PVC due to prolonged heating at high temperatures. The evaporated solvent is condensed and recovered as a recycled dissolved phase. PVC, as a non-volatile solute, remains at the bottom of the evaporator and is discharged in a molten or softened state, allowing for direct granulation to obtain recycled PVC. The high-boiling-point, unevaporated phase stabilizer, tributyl phosphate, is dispersed within the PVC, with a mass percentage of approximately 2% to 6%. Tributyl phosphate acts as a plasticizer and heat stabilizer, enhancing the plasticity and thermal stability of PVC and improving its processing performance. Recycled PVC does not require additional water washing and desalination, resulting in low processing costs.

[0024] A preferred embodiment of the treatment process for marine-sourced polyvinyl chloride foam waste is as follows: the treatment method in step S3 is to introduce the separated desalination phase layer into a vacuum flash evaporation device and perform flash evaporation under conditions of 10kPa~30kPa and 80~120℃ to remove water and precipitate salt. The remaining liquid phase is then recycled as the desalination phase.

[0025] By adopting the above technical solution, the desalination phase layer is preheated to 80~120℃ and then enters the flash tank through a throttling valve. The flash tank maintains a low pressure of 10kPa~30kPa, causing the lower-boiling-point water in the desalination phase layer to rapidly vaporize into water vapor, which is discharged from the top and condensed. The remaining liquid is concentrated, and the dissolved salts, due to water evaporation, exceed saturation and crystallize out, settling at the bottom and being collected through periodic discharge. The diols in the remaining liquid, due to their higher boiling point, are essentially non-volatile and remain at the bottom of the flash tank, which can be recycled back to the dissolution step as a desalination phase. This step simultaneously achieves dehydration, salt precipitation, and desalination phase regeneration, eliminating the need for additional desalination equipment, and allowing for salt crystallization and recovery, avoiding the discharge of high-salt wastewater.

[0026] In summary, the phase-separation type organic solvent and marine-source polyvinyl chloride foam waste treatment process of this application has the following beneficial effects: High purity of recycled materials: The salt residue of recycled polyvinyl chloride is ≤0.1%, which meets the industry standard for recycled granulation and can be directly utilized as a resource. Environmentally friendly and low-waste: No water washing or desalination is required, no high-salt wastewater is generated, salt can be crystallized and recovered, and solid impurities are disposed of in a harmless manner. Cost controllable: The two-phase solvent is recycled with a recovery rate of ≥92%, resulting in low overall operating costs. Attached Figure Description

[0027] Figure 1 This is a reference diagram of the implementation process of Example 1. Detailed Implementation

[0028] The technical solutions in the embodiments are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the following embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Example 1

[0029] A process for treating marine-sourced polyvinyl chloride (PVC) foam waste uses a phase-separation type organic solvent to treat the waste.

[0030] The phase-separated organic solvent consists of a dissolving phase, a desalting phase, and a phase stabilizer in a volume ratio of 100:100:1. The dissolving phase consists of limonene and p-methoxycyclohexanone in a volume ratio of 70:30, the desalting phase is ethylene glycol, and the phase stabilizer is tributyl phosphate.

[0031] Marine-sourced polyvinyl chloride foam waste: Polyvinyl chloride foam floats were taken from coastal aquaculture areas, crushed into fragments with a particle size of ≤5cm by a crusher, and the moisture content was measured to be 35wt% and the salt content was 5wt%.

[0032] refer to Figure 1 The treatment process steps for this marine-sourced polyvinyl chloride foam waste are as follows.

[0033] S1. Following a mass ratio of 1 kg of marine-sourced PVC foam waste to 10 L of phase-separating organic solvent, the waste was added to the solvent and heated to 60°C. The mixture was stirred at 200 rpm for 20 minutes to ensure complete dissolution of the PVC. The mixture was then allowed to settle and separate into two phases. The dissolved phase and the desalinated phase were collected separately and filtered to remove impurities. After settling naturally for 40 minutes, the system separated into two distinct phases: an upper layer of dissolved PVC and a lower layer of ethylene glycol desalinated phase. Both layers were then discharged and filtered through a 200-mesh filter to remove any entrained impurities such as silt and algae.

[0034] In step S2, the dissolved phase layer is introduced into a thin-film evaporator. The scraper rotates at 180 rpm, and vacuum distillation is performed at 3 kPa and 140°C. The solvent is first evaporated and then condensed for recovery, achieving a recovery rate of 93.5% and a water content of 0.03 wt%. The condensed solvent is returned to step S1 for recycling. The unevaporated residue, a molten mixture of stabilizer and PVC, is discharged from the bottom of the evaporator. After cooling, crushing, and granulation, recycled PVC granules are obtained. Testing revealed a salt residue content of 0.06 wt% in the recycled PVC.

[0035] In step S3, the separated desalted phase layer is introduced into a vacuum flash evaporator. Flash evaporation is performed at 20 kPa and 100°C to remove moisture and precipitate salt. The remaining liquid phase, ethylene glycol, is recycled as the desalted phase. Flash evaporation continues until the moisture content of the remaining liquid phase is ≤5 wt%. The evaporated and condensed water is discharged, and the precipitated salt is collected periodically from the bottom of the tank. The remaining liquid phase after flash evaporation is mainly ethylene glycol, with a recovery rate of 96.3% and a purity of 99.2%. This recovered ethylene glycol is then recycled back to step S1 as the desalted phase. Example 2

[0036] A process for treating marine-sourced polyvinyl chloride (PVC) foam waste uses a phase-separation type organic solvent to treat the waste.

[0037] The phase-separated organic solvent consists of a dissolving phase, a desalting phase, and a phase stabilizer in a volume ratio of 100:80:0.5. The dissolving phase consists of limonene and p-methoxycyclohexanone in a volume ratio of 60:40, the desalting phase is diethylene glycol, and the phase stabilizer is tributyl phosphate.

[0038] Marine-sourced polyvinyl chloride foam waste: Polyvinyl chloride foam floats were taken from coastal aquaculture areas, crushed into fragments with a particle size of ≤5cm by a crusher, and the moisture content was measured to be 35wt% and the salt content was 5wt%.

[0039] The treatment process for marine-derived polyvinyl chloride foam waste is as follows.

[0040] S1. Following a mass ratio of 1 kg of marine-sourced PVC foam waste to 8 L of phase-separating organic solvent, the waste was added to the solvent and heated to 50°C. The mixture was stirred at 200 rpm for 20 minutes to ensure complete dissolution of the PVC. The mixture was then allowed to settle and separate into two phases. The dissolved phase and the desalinated phase were collected separately and filtered to remove impurities. After settling naturally for 40 minutes, the system separated into two distinct phases: an upper layer of dissolved PVC and a lower layer of diethylene glycol desalinated phase. Both layers were then discharged and filtered through a 200-mesh filter to remove any entrained impurities such as silt and algae.

[0041] In step S2, the dissolved phase layer is introduced into a thin-film evaporator. The scraper rotates at 180 rpm, and vacuum distillation is performed at 1 kPa and 120°C. The solvent is first evaporated and then condensed for recovery, achieving a recovery rate of 92.8% and a water content of 0.06 wt%. The condensed solvent is returned to step S1 for recycling. The unevaporated residue, a molten mixture of stabilizer and PVC, is discharged from the bottom of the evaporator. After cooling, crushing, and granulation, recycled PVC granules are obtained. Testing revealed a salt residue content of 0.09 wt% in the recycled PVC.

[0042] In step S3, the separated desalted phase layer is introduced into a vacuum flash evaporator and flashed at 10 kPa and 80°C to remove moisture and precipitate salt. The remaining liquid phase, diethylene glycol, is then recycled as the desalted phase. Flash evaporation continues until the moisture content of the remaining liquid phase is ≤5 wt%. The water is evaporated, condensed, and discharged, while the precipitated salt is collected periodically from the bottom of the tank. The remaining liquid phase after flash evaporation is mainly diethylene glycol, with a recovery rate of 95.7% and a purity of 98.1%. This recovered diethylene glycol is then recycled back to step S1 as the desalted phase. Example 3

[0043] A process for treating marine-sourced polyvinyl chloride (PVC) foam waste uses a phase-separation type organic solvent to treat the waste.

[0044] The phase-separated organic solvent consists of a dissolving phase, a desalting phase, and a phase stabilizer in a volume ratio of 100:120:1.5. The dissolving phase consists of limonene and p-methoxycyclohexanone in a volume ratio of 80:20, the desalting phase is triethylene glycol, and the phase stabilizer is tributyl phosphate.

[0045] Marine-sourced polyvinyl chloride foam waste: Polyvinyl chloride foam floats were taken from coastal aquaculture areas, crushed into fragments with a particle size of ≤5cm by a crusher, and the moisture content was measured to be 35wt% and the salt content was 5wt%.

[0046] The treatment process for marine-derived polyvinyl chloride foam waste is as follows.

[0047] S1. Following a mass ratio of 1 kg of marine-sourced PVC foam waste to 12 L of phase-separating organic solvent, the waste was added to the solvent and heated to 70°C. The mixture was stirred at 200 rpm for 20 minutes to ensure complete dissolution of the PVC. The mixture was then allowed to settle and separate into two phases. The dissolved phase and the desalted phase were collected separately and filtered to remove impurities. After settling naturally for 40 minutes, the system separated into two distinct phases: an upper layer of dissolved PVC and a lower layer of triethylene glycol desalted phase. Both layers were then discharged and filtered through a 200-mesh filter to remove entrained impurities such as silt and algae.

[0048] In step S2, the dissolved phase layer is introduced into a thin-film evaporator. The scraper rotates at 180 rpm, and vacuum distillation is performed at 5 kPa and 160°C. The solvent is first evaporated and then condensed for recovery, achieving a recovery rate of 94.1% and a water content of 0.04 wt%. The condensed solvent is returned to step S1 for recycling. The unevaporated residue, a molten mixture of stabilizer and PVC, is discharged from the bottom of the evaporator. After cooling, crushing, and granulation, recycled PVC granules are obtained. Testing revealed a salt residue content of 0.07 wt% in the recycled PVC.

[0049] In step S3, the separated desalted phase layer is introduced into a vacuum flash evaporator and flashed at 30 kPa and 120°C to remove moisture and precipitate salt. The remaining liquid phase, triethylene glycol, is recycled as the desalted phase. Flash evaporation continues until the moisture content of the remaining liquid phase is ≤5 wt%. The water is evaporated, condensed, and discharged, while the precipitated salt is collected periodically from the bottom of the tank. The remaining liquid phase after flash evaporation is mainly triethylene glycol, with a recovery rate of 96.1% and a purity of 98.5%. This recovered triethylene glycol is then recycled back to step S1 as the desalted phase.

[0050] Comparative Example 1 A treatment process for marine-sourced polyvinyl chloride (PVC) foam waste is disclosed. In this comparative example, compared to Example 1, p-methoxycyclohexanone is replaced with an equal volume of cyclohexanone, while other experimental conditions remain the same. This results in the formation of an emulsion layer between the two phases in step S1 due to the stronger polarity of cyclohexanone, leading to increased solubility between the two phases. The two phases are collected, while the emulsion layer is discarded. In step S2, the solvent recovery rate is 88.3%, the water content is 1.69 wt%, and the salt content of the recycled PVC increases to 0.74 wt%. In step S3, the desalination phase recovery rate is 90.4%, and the purity is 92.3%.

[0051] Comparative Example 2 A process for treating marine-sourced polyvinyl chloride (PVC) foam waste is described in this comparative example. Compared to Example 1, the solution phase is changed from a mixture of limonene and p-methoxycyclohexanone to pure limonene with the same total volume. Other experimental conditions remain the same, except for step S1. Step S1 can only swell the PVC but cannot completely dissolve it.

[0052] Comparative Example 3 A treatment process for marine-derived polyvinyl chloride (PVC) foam waste is disclosed in this comparative example. Compared to Example 1, the solution phase is changed from a mixture of limonene and p-methoxycyclohexanone to pure methoxycyclohexanone with the same total volume. Other experimental conditions remain the same, except for steps S1 and S2. In step S1, the solvent cannot separate into two phases but remains a single turbid phase. Salt and water are mixed in the organic liquid containing PVC, leading to direct vacuum distillation of the single turbid phase in step S2. The solvent recovery rate is 84.6%, the water content is 3.1 wt%, and the salt residue in the recycled PVC reaches 2.45 wt%.

[0053] Comparative Example 4 A treatment process for marine-derived polyvinyl chloride (PVC) foam waste is disclosed. Compared to Example 1, this comparative example removes the phase stabilizer tributyl phosphate, while other experimental conditions remain the same. This results in extremely slow phase separation. After natural settling for 3 hours, an emulsion layer forms between the two phases in step S1. Both phases are collected, while the emulsion layer is discarded. The solvent recovery rate in step S2 is 75.6%, and the water content is 1.93 wt%. The salt content of the recycled PVC in step S2 increases to 1.82 wt%. The desalination phase recovery rate in step S3 is 81.5%, and the purity is 86.4%.

[0054] Experimental Example 1 The recycled polyvinyl chloride prepared in Examples 1-3 and Comparative Examples 1, 3, and 4, as well as the waste polyvinyl chloride foam floats used in each example and comparative example (hereinafter referred to as "waste material") and commercially available new polyvinyl chloride foam floats (hereinafter referred to as "new material") were heated to 180°C in the same manner to melt and form samples, and the following mechanical property tests were performed.

[0055] Tensile strength and elongation at break were determined according to GB / T 1040.2-2022 "Determination of Tensile Properties of Plastics". Impact strength was determined according to GB / T 1043.1-2008 "Determination of Impact Properties of Simply Supported Beams of Plastics". Test data are shown in Table 1.

[0056] Table 1 Mechanical property testing of polyvinyl chloride Tensile strength (MPa) Elongation at break % Impact strength kJ / m 2 ]] Example 1 43.7 48 4.3 Example 2 42.5 45 4.2 Example 3 41.2 47 4.4 Comparative Example 1 37.9 40 3.9 Comparative Example 3 34.8 36 3.5 Comparative Example 4 35.4 38 3.7 waste 26.3 29 2.8 New materials 44.1 50 4.5 Table 1 shows that the mechanical properties of the recycled PVC prepared in Examples 1-3 are close to those of virgin material, recovering about 95% of the mechanical properties of virgin material, and are significantly better than those of waste material. In Comparative Example 1, replacing p-methoxycyclohexanone with cyclohexanone increased the salt content of the recycled PVC, and the mechanical properties decreased compared to Examples 1-3. In Comparative Example 3, changing the solution phase from a mixture of limonene and p-methoxycyclohexanone to pure methoxycyclohexanone significantly increased the salt content of the recycled PVC, and the mechanical properties decreased significantly compared to Examples 1-3. In Comparative Example 4, removing the phase stabilizer tributyl phosphate significantly increased the salt content of the recycled PVC, and the mechanical properties decreased significantly compared to Examples 1-3.

[0057] In Comparative Example 1, cyclohexanone was used instead of p-methoxycyclohexanone. Since cyclohexanone is a strongly polar ketone solvent, its miscibility with ethylene glycol is significantly higher than that of p-methoxycyclohexanone with ethylene glycol. After heating and stirring, a thicker emulsion layer is formed. Some ethylene glycol enters the dissolving phase, and some cyclohexanone enters the desalting phase. The interface between the two phases is blurred. Because the emulsion layer encapsulates the salt, it is discarded, resulting in a decrease in solvent recovery rate and an increase in loss.

[0058] Comparative Example 2 shows that pure limonene cannot effectively dissolve polyvinyl chloride; it can only cause the surface to swell but cannot regenerate the polyvinyl chloride.

[0059] Comparative Example 3 uses cyclohexanone, which is miscible with ethylene glycol. Under stirring and heating conditions, it forms a stable emulsion that fails to separate upon standing. This results in salts not being carried away by the separated phase and remaining almost entirely in the recycled PVC, severely reducing the mechanical properties of the recycled PVC. Furthermore, the solvent recovery rate is low, the water content is high, and losses are significant, increasing production costs. This indicates that phase separation followed by desalination is a necessary path to achieve the technical effects of this application.

[0060] Tributyl phosphate has extremely low surface tension and thus possesses demulsifying properties, causing a clear separation between the dissolved phase and the desalted phase. In Comparative Example 4, the removal of the phase stabilizer tributyl phosphate made separation between the dissolved and desalted phases difficult, resulting in the formation of an emulsion layer between them. This increased solvent loss, led to an increase in the salt content of the recycled PVC, and reduced the mechanical properties of the recycled PVC.

[0061] Examples 1-3 used limonene and p-methoxycyclohexanone in a volume ratio of (60-80):(20-40), achieving sufficient solubility and stable phase equilibrium. Single-component limonene or p-methoxycyclohexanone, or simply replacing p-methoxycyclohexanone with cyclohexanone, cannot simultaneously achieve both sufficient solubility and stable phase equilibrium. This application uses saturated diol as the desalting phase and tributyl phosphate as a phase stabilizer to achieve the separation of polyvinyl chloride from salts and moisture. The recycled polyvinyl chloride product has fewer impurities, better performance, higher solvent recovery rate, and higher purity, improving the utilization rate of organic solvents. The recycled polyvinyl chloride solution of this application meets the requirements of economy and greenness and has industrial promotion value.

[0062] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A phase-separated organic solvent, characterized in that, It includes a dissolving phase, a desalting phase, and a phase stabilizer; the dissolving phase includes limonene and p-methoxycyclohexanone; the desalting phase is a saturated diol; and the phase stabilizer is tributyl phosphate.

2. The phase-separated organic solvent according to claim 1, characterized in that, The desalting phase is ethylene glycol, diethylene glycol, or triethylene glycol.

3. The phase-separated organic solvent according to claim 1, characterized in that, The volume ratio of the dissolved phase, the desalted phase, and the phase stabilizer is 100:(80~120):(0.5~1.5).

4. The phase-separated organic solvent according to claim 1, characterized in that, The volume ratio of limonene to p-methoxycyclohexanone is (60~80):(20~40).

5. A treatment process for marine-sourced polyvinyl chloride foam waste, characterized in that, The phase-separation type organic solvent according to any one of claims 1 to 4 is used to treat marine-source polyvinyl chloride foam waste; The treatment process for marine-sourced polyvinyl chloride foam waste includes: S1, add marine-sourced polyvinyl chloride foam waste to the phase-separation type organic solvent, heat to dissolve, let stand to separate layers, collect the dissolved phase layer and the desalination phase layer respectively, and filter to remove impurities; S2, the dissolved phase layer is evaporated, and the evaporated dissolved phase is recycled to obtain polyvinyl chloride containing the stabilizer; S3, the desalination phase in the desalination phase layer is separated and recycled.

6. The treatment process for marine-sourced polyvinyl chloride foam waste according to claim 5, characterized in that, The ratio of the mass of marine-sourced polyvinyl chloride foam waste to the volume of the phase-separated organic solvent is 1 kg: (8~12) L.

7. The treatment process for marine-sourced polyvinyl chloride foam waste according to claim 5, characterized in that, The heating temperature in step S1 is 50~70℃, and stirring is performed while heating.

8. The treatment process for marine-sourced polyvinyl chloride foam waste according to claim 5, characterized in that, The processing method of step S2 is as follows: the dissolved phase layer is introduced into a thin film evaporator and subjected to vacuum distillation at 1kPa~5kPa and 120~160℃. The solvent is evaporated first and then condensed and recovered. The condensed solvent is recycled as the dissolved phase. The unevaporated residue is a mixture of the stabilizer and polyvinyl chloride. The mixture is regenerated to obtain recycled polyvinyl chloride.

9. The treatment process for marine-sourced polyvinyl chloride foam waste according to claim 5, characterized in that, The processing method in step S3 is as follows: the desalted phase layer obtained by separation is introduced into a vacuum flash evaporation device, and flash evaporation is carried out under the conditions of 10kPa~30kPa and 80~120℃ to remove water and precipitate salt. The remaining liquid phase is recycled as the desalted phase again.

Images