A method for harmless digestion and recovery of waste foamed polystyrene material containing a fat-containing bromine flame-retardant component

Abstract

The application discloses a harmless digestion and recycling method of waste foamed polystyrene material containing fat bromine flame-retardant components, innovatively combines the phase transfer catalysis technology with the strong alkali debromination process, realizes 100% efficient harmless digestion of the fat bromine flame-retardant components in the foamed polystyrene, then separates the bromine-containing aqueous solution and the polystyrene-containing organic solution generated in the digestion process through efficient water washing, and then respectively carries out bromine extraction treatment and polystyrene recycling and granulation, so that the bromine resources and the polystyrene material are completely recycled and recycled. The regenerated polystyrene material obtained by the application contains less than 0.01% of residual fat bromine compounds, the whole recycling process does not generate harmful waste, and has the characteristics of green and sustainable development.

Description

Technical Field

[0001] This invention relates to a method for the harmless disposal and recycling of waste expanded polystyrene materials containing fatty bromine flame retardant components, belonging to the technical field of waste polystyrene material recycling and reuse. Background Technology

[0002] Expanded polystyrene (EPS) and XPS are commonly used as exterior wall insulation materials in the construction industry due to their excellent thermal insulation properties and low cost. To improve their flame retardant properties, many EPS and XPS insulation materials contain aliphatic bromine flame retardants, such as hexabromocyclododecane (HBCD). HBCD itself, due to its persistence, potential toxicity, and potential harm to the ecological environment and human health, has been listed as a persistent organic pollutant by the Stockholm Convention and is completely banned in my country. However, as of now, a large amount of expanded polystyrene insulation material containing HBCD still exists in existing buildings in my country. In the future, this material will be discarded during building renovation and demolition. If conventional landfill or incineration is used for disposal, it will cause huge pollution to the environment and a great waste of polystyrene resources. Therefore, it is urgent to develop harmless disposal and recycling technologies for waste expanded polystyrene materials containing aliphatic bromine flame retardants, especially those containing HBCD.

[0003] A search of existing patents revealed few reports on the harmless recycling and reuse technology of waste expanded polystyrene materials containing fatty brominated flame retardants. Instead, there were more reports on the separate aspects of expanded polystyrene material recycling and the decomposition treatment of fatty brominated flame retardants, especially HBCD compounds.

[0004] Regarding the recycling and utilization of expanded polystyrene (EPS) materials, Chinese patent CN202410344555.1 describes a method for obtaining recycled EPS granules by washing, crushing, melting, and extruding granulation of recycled EPS; Chinese patent CN201610585197.9 discloses an environmentally friendly method for recycling EPS waste using a dissolution process and a supercritical CO2 extraction process; in addition, related patents (Chinese patents CN201610417697.1 and CN201610417699.0) have reported applications of using recycled polystyrene materials to prepare other composite materials; however, the above patents only report on the recycling of EPS materials and do not mention methods for the recovery and harmless treatment of chemical additives contained in EPS materials.

[0005] Regarding the treatment of HBCD compounds, Chinese patent CN202311859412.6 describes a method for treating soil contaminated with hexabromocyclododecane using thermal decomposition. However, while this method can effectively treat HBCD, it also causes problems such as air pollution and waste of bromine resources. Chinese patent CN202010539693.7 discloses a method for degrading hexabromocyclododecane using graphitic carbon nitride. This method uses graphitic carbon nitride as a catalyst and achieves the harmless degradation of HBCD through ultraviolet photocatalytic degradation in a mixed solvent system. Chinese patent CN201910163737.8 reports a method for degrading hexabromocyclododecane compounds using Pseudomonas aeruginosa HS9, achieving low-cost and low-energy-consumption harmless treatment. Although the above patents can effectively decompose HBCD, none of them can achieve the recovery and reuse of bromine resources in HBCD.

[0006] Normally, harmlessly dissolving HBCD and other aliphatic bromine-containing flame-retardant components in waste flame-retardant expanded polystyrene materials, while simultaneously recovering and extracting bromine and recycling polystyrene materials, is of great significance for developing a resource circular economy. Based on this, this invention innovatively adopts a strong alkali debromination process assisted by phase transfer catalysis technology to achieve 100% efficient and harmless dissolution of aliphatic bromine-containing flame-retardant components in expanded polystyrene. At the same time, through efficient water washing separation technology, the bromine-containing aqueous solution and polystyrene-containing organic solution generated during the dissolution process are rapidly separated. Finally, through bromine extraction treatment and polystyrene recycling granulation, the complete recovery and recycling of bromine resources and polystyrene materials are achieved. Summary of the Invention

[0007] The purpose of this invention is to address the difficulties in simultaneously achieving the harmless decomposition of bromine-containing flame-retardant components in expanded polystyrene (EPS) materials containing aliphatic bromine, and the incomplete recovery of bromine and EPS materials. This invention provides a novel method that simultaneously achieves both goals. Specifically, the EPS material containing aliphatic bromine flame-retardant components is dissolved in an organic solvent. A strong-base debromination process assisted by phase transfer catalysis is employed. The alkaline groups in the inorganic phase are introduced into the organic phase as organic bases under the catalysis of the phase transfer catalyst. This promotes sufficient contact between the alkaline substances and bromides, while simultaneously improving the debromination efficiency of the reaction system, achieving 100% efficient and harmless decomposition of the aliphatic bromine flame-retardant components in the EPS. Subsequently, a high-efficiency water washing separation technology is used to rapidly separate the bromine-containing aqueous solution and the EPS organic solution generated during the decomposition process. The separated bromine-containing aqueous solution undergoes bromine extraction treatment, the EPS organic solution undergoes solvent separation, and the EPS is recycled and granulated. This method can simultaneously achieve the complete recovery and recycling of bromine resources and EPS materials.

[0008] The technical solution adopted in this invention is as follows:

[0009] A method for the harmless disposal and recycling of waste expanded polystyrene material containing aliphatic bromine flame retardant components, the method mainly includes the following steps:

[0010] The first step involves pulverizing the waste expanded polystyrene material containing fatty brominated flame retardant components, dissolving the pulverized material in an organic solvent to obtain an organic solution containing expanded polystyrene; the fatty brominated flame retardant components in the waste expanded polystyrene material containing fatty brominated flame retardant components are one or more of hexabromocyclododecane, octabromoether, methyl octabromoether, and brominated styrene-butadiene-styrene block copolymer.

[0011] The second step is to filter the polystyrene organic solution obtained in the first step to remove the solid insoluble matter.

[0012] The third step is to add a phase transfer catalyst to the filtered polystyrene organic solution, stir for a period of time, add an alkaline solution or solid alkali, and then, under the catalytic action of the phase transfer catalyst, maintain the system temperature and continue stirring for a period of time to debrominate the bromine-based flame retardant components in the polystyrene organic solution.

[0013] Fourth step: Add water to the polystyrene organic solution obtained in the third step, maintain the system temperature, stir and wash, and after standing, separate the organic phase and the aqueous phase. The organic phase yields a purified polystyrene organic solution, and the aqueous phase yields an aqueous solution containing bromide and alkali.

[0014] The fifth step involves distilling the purified polystyrene organic solution under reduced pressure or normal pressure at a certain temperature, or adding it to hot water to remove the organic solvent. Then, the polystyrene-based material after solvent removal is granulated, cooled, and dried to obtain recycled polystyrene granules.

[0015] The sixth step involves neutralizing the aqueous solution containing bromide and alkali with acid and alkali, and then extracting the bromine component.

[0016] Preferably, the mass of the organic solvent in the first step is 0.5-100 times that of the pulverized material.

[0017] Preferably, the organic solvent described in the first step is composed of one or more of toluene, xylene, benzene, chlorobenzene, chloroform, dichloromethane, dichloroethane, acetonitrile, and tetrahydrofuran.

[0018] Preferably, the phase transfer catalyst described in the third step is composed of one or more of the following quaternary or tertiary ammonium salts: tetramethylammonium bromide, tetramethylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride, tetrapropylammonium bromide, tetrapropylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, and triethylamine.

[0019] Preferably, the amount of phase transfer catalyst used in the third step is 0.1%-5% of the mass of the waste expanded polystyrene material containing aliphatic bromine flame retardant components.

[0020] Preferably, the alkali in the alkaline solution described in the third step consists of one or more of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, and ammonia water.

[0021] Preferably, the solid alkali described in the third step is composed of one or more of sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide.

[0022] Preferably, in the third step, the amount of alkali or solid alkali used in the alkaline solution is 0.1%-10% of the mass of the polystyrene organic solution.

[0023] Preferably, in the third step, the system temperature is maintained at 0℃-100℃, and the stirring time for both steps is 0.1-24h.

[0024] Preferably, the mass of the water in the fourth step is 1%-100% of the mass of the polystyrene organic solution.

[0025] Preferably, the fourth step of maintaining the system temperature means maintaining the system temperature at 0℃-100℃.

[0026] Preferably, the reduced pressure or atmospheric pressure distillation temperature described in step five is 50-120°C.

[0027] Preferably, the hot water in step 5 is 60-100℃.

[0028] Compared with existing expanded polystyrene (EPS) material recycling technologies, this invention is characterized by being green, simple, and efficient. Addressing the low efficiency of traditional alkali-based debromination processes, it innovatively employs a strong alkali debromination process assisted by phase transfer catalysis technology. This achieves 100% efficient and harmless decomposition of aliphatic bromine flame-retardant components in waste flame-retardant EPS materials, while simultaneously realizing the complete recovery of bromine and the EPS material. The resulting recycled EPS material contains less than 0.01% residual aliphatic bromine flame-retardant components. The organic solvents and aqueous solutions used in the process can be recycled, and the entire recycling process does not generate harmful waste, embodying the concept of green and sustainable development. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the method of the present invention. Detailed Implementation

[0030] The present invention is further illustrated below with reference to the embodiments; these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention; experimental methods in the following embodiments that do not specify specific conditions are generally performed according to conventional conditions in the art; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from conventional markets and other commercial channels; any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

[0031] Example 1

[0032] The first step is to crush 1 kg of waste expanded polystyrene material containing HBCD, dissolve the crushed material in 2 kg of toluene to obtain a toluene solution containing expanded polystyrene.

[0033] The second step is to filter the polystyrene-toluene solution obtained in the first step to remove the solid insoluble matter.

[0034] The third step involves adding 2g of tetramethylammonium chloride to the filtered polystyrene-toluene solution, stirring for 1 hour, then adding 500g of 20% sodium hydroxide solution. Subsequently, under the catalytic action of a phase transfer catalyst, the system temperature is maintained at 5℃, and stirring is continued for 24 hours to debrominate HBCD in the polystyrene-toluene solution.

[0035] Fourth step: Add 1 kg of water to the polystyrene toluene solution obtained in the third step, keep the system temperature at 25°C, stir and wash, and after standing, separate the organic phase and the aqueous phase. The organic phase is a purified polystyrene toluene solution, and the aqueous phase is an aqueous solution containing sodium bromide and sodium hydroxide.

[0036] The fifth step involves distilling the purified polystyrene toluene solution under reduced pressure at 100°C to remove the organic solvent toluene. The polystyrene-based material after solvent removal is then granulated, cooled, and dried to obtain recycled polystyrene granules.

[0037] The sixth step involves neutralizing the aqueous solution containing sodium bromide and sodium hydroxide with acid and alkali, and then extracting the bromine component.

[0038] The number-average molecular weight (Mn), glass transition temperature (Tg), and residual HBCD content of the recycled polystyrene obtained in this embodiment are shown in Table 1 below.

[0039] Table 1

[0040]

[0041] Example 2

[0042] The first step is to crush 2 kg of waste expanded polystyrene material containing HBCD, dissolve the crushed material in 3 kg of benzene to obtain a benzene solution containing expanded polystyrene.

[0043] The second step is to filter the polystyrene-benzene solution obtained in the first step to remove the solid insoluble matter.

[0044] The third step involves adding 50g of tetrapropylammonium bromide to the filtered polystyrene-benzene solution, stirring for 12 hours, then adding 200g of potassium hydroxide and 100g of sodium hydroxide solid. Subsequently, under the catalytic action of a phase transfer catalyst, the system temperature is maintained at 80℃, and stirring is continued for 18 hours to debrominate HBCD in the polystyrene-benzene solution.

[0045] Fourth step: Add 3 kg of water to the polystyrene benzene solution obtained in the third step, keep the system temperature at 60℃, stir and wash, and after standing, separate the organic phase and the aqueous phase. The organic phase is a purified polystyrene benzene solution, and the aqueous phase is an aqueous solution containing potassium bromide, sodium bromide, potassium hydroxide, and sodium hydroxide.

[0046] The fifth step involves adding the purified polystyrene-benzene solution to hot water at 85°C to remove the organic solvent benzene. The polystyrene-based material after solvent removal is then granulated, cooled, and dried to obtain recycled polystyrene granules.

[0047] The sixth step involves neutralizing the aqueous solution containing potassium bromide, sodium bromide, potassium hydroxide, and sodium hydroxide with acid and alkali, and then extracting the bromine component.

[0048] The number-average molecular weight (Mn), glass transition temperature (Tg), and residual HBCD content of the recycled polystyrene obtained in this embodiment are shown in Table 2 below.

[0049] Table 2

[0050]

[0051] Example 3

[0052] The first step is to crush 5 kg of waste expanded polystyrene material containing HBCD, dissolve the crushed material in 20 kg of dichloroethane to obtain a dichloroethane solution containing expanded polystyrene.

[0053] The second step is to filter the polystyrene dichloroethane solution obtained in the first step to remove the solid insoluble matter.

[0054] The third step involves adding 150g of tetrabutylammonium bromide to the filtered polystyrene dichloroethane solution, stirring for 6 hours, then adding 1kg of sodium carbonate and 1kg of sodium hydroxide solid. Subsequently, under the catalytic action of a phase transfer catalyst, the system temperature is maintained at 50℃, and stirring is continued for 3 hours to debrominate HBCD in the polystyrene dichloroethane solution.

[0055] Fourth step: Add 10 kg of water to the polystyrene dichloroethane solution obtained in the third step, keep the system temperature at 80℃, stir and wash, and after standing, separate the organic phase and the aqueous phase. The organic phase is a purified polystyrene dichloroethane solution, and the aqueous phase is an aqueous solution containing sodium bromide, sodium carbonate and sodium hydroxide.

[0056] The fifth step involves distilling the purified polystyrene solution in dichloroethane at 100°C under normal pressure to remove the organic solvent dichloroethane. The polystyrene-based material after solvent removal is then granulated, cooled, and dried to obtain recycled polystyrene granules.

[0057] The sixth step involves neutralizing the aqueous solution containing sodium bromide, sodium carbonate, and sodium hydroxide with acid and alkali, and then extracting the bromine component.

[0058] The number-average molecular weight (Mn), glass transition temperature (Tg), and residual HBCD content of the recycled polystyrene obtained in this embodiment are shown in Table 3 below.

[0059] Table 3

[0060]

[0061] Example 4

[0062] The first step is to crush 2 kg of waste expanded polystyrene material containing methyl octabromoether, dissolve the crushed material in 10 kg of chlorobenzene solvent, and obtain a chlorobenzene solution containing expanded polystyrene.

[0063] The second step is to filter the polystyrene-chlorobenzene solution obtained in the first step to remove the solid insoluble matter.

[0064] The third step involves adding 25g of tetraethylammonium chloride and 25g of triethylamine to the filtered polystyrene chlorobenzene solution, stirring for 3 hours, then adding 3kg of 30% potassium hydroxide solution. Subsequently, under the catalytic action of a phase transfer catalyst, the system temperature is maintained at 50℃, and stirring is continued for 12 hours to debrominate the methyl octabromoether in the polystyrene chlorobenzene solution.

[0065] Fourth step: Add 6 kg of water to the polystyrene chlorobenzene solution obtained in the third step, keep the system temperature at 50℃, stir and wash, and after standing, separate the organic phase and the aqueous phase. The organic phase is a purified polystyrene chlorobenzene solution, and the aqueous phase is an aqueous solution containing potassium bromide and potassium hydroxide.

[0066] The fifth step involves distilling the purified polystyrene chlorobenzene solution under reduced pressure at 110°C to remove the organic solvent chlorobenzene. The polystyrene-based material after solvent removal is then granulated, cooled, and dried to obtain recycled polystyrene granules.

[0067] The sixth step involves neutralizing the aqueous solution containing potassium bromide and potassium hydroxide with acid and alkali, and then extracting the bromine component.

[0068] The number-average molecular weight (Mn), glass transition temperature (Tg), residual HBCD, and methyl octabromoether content of the recycled polystyrene obtained in this embodiment are shown in Table 4 below.

[0069] Table 4

[0070]

[0071]

[0072] Example 5

[0073] The first step is to crush 1 kg of waste expanded polystyrene material containing octabromoether, dissolve the crushed material in 10 kg of chloroform solvent, and obtain a chloroform solution containing expanded polystyrene.

[0074] The second step is to filter the polystyrene chloroform solution obtained in the first step to remove the solid insoluble matter.

[0075] The third step involves adding 15g of tetramethylammonium bromide to the filtered polystyrene chloroform solution, stirring for 2 hours, then adding 1kg of sodium carbonate solid. Subsequently, under the catalytic action of a phase transfer catalyst, the system temperature is maintained at 30℃, and stirring is continued for 6 hours to debrominate the octabromoether in the polystyrene chloroform solution.

[0076] Fourth step: Add 10 kg of water to the polystyrene chloroform solution obtained in the third step, keep the system temperature at 60℃, stir and wash, and after standing, separate the organic phase and the aqueous phase. The organic phase is a chloroform solution of purified polystyrene, and the aqueous phase is an aqueous solution containing sodium bromide and sodium carbonate.

[0077] The fifth step involves distilling the purified polystyrene chloroform solution at 65°C under normal pressure to remove the organic solvent chloroform. The polystyrene-based material after solvent removal is then granulated, cooled, and dried to obtain recycled polystyrene granules.

[0078] The sixth step involves neutralizing the aqueous solution containing sodium bromide and sodium carbonate with acid and alkali, and then extracting the bromine component.

[0079] The number-average molecular weight (Mn), glass transition temperature (Tg), and residual octabromoether content of the recycled polystyrene obtained in this embodiment are shown in Table 5 below.

[0080] Table 5

[0081]

[0082] Example 6

[0083] The first step involves crushing 5 kg of waste expanded polystyrene material containing brominated styrene-butadiene-styrene block copolymer, dissolving the crushed material in 20 kg of dichloroethane solvent to obtain a dichloroethane solution containing expanded polystyrene.

[0084] The second step is to filter the polystyrene dichloroethane solution obtained in the first step to remove the solid insoluble matter.

[0085] The third step involves adding 100g of tetrabutylammonium bromide to the filtered polystyrene dichloroethane solution, stirring for 5 hours, then adding 1.25kg of sodium hydroxide solid. Subsequently, under the catalytic action of a phase transfer catalyst, the system temperature is maintained at 60℃, and stirring is continued for 10 hours to debrominate the brominated styrene-butadiene-styrene block copolymer in the polystyrene dichloroethane solution.

[0086] Fourth step: Add 20 kg of water to the polystyrene dichloroethane solution obtained in the third step, keep the system temperature at 80℃, stir and wash, and after standing, separate the organic phase and the aqueous phase. The organic phase is a purified polystyrene dichloroethane solution, and the aqueous phase is an aqueous solution containing sodium bromide and sodium hydroxide.

[0087] The fifth step involves distilling the purified polystyrene solution in dichloroethane at 85°C under normal pressure to remove the organic solvent dichloroethane. The polystyrene-based material after solvent removal is then granulated, cooled, and dried to obtain recycled polystyrene granules.

[0088] The sixth step involves neutralizing the aqueous solution containing sodium bromide and sodium hydroxide with acid and alkali, and then extracting the bromine component.

[0089] The number-average molecular weight (Mn), glass transition temperature (Tg), and residual octabromoether content of the recycled polystyrene obtained in this embodiment are shown in Table 6 below.

[0090] Table 6

[0091]

[0092] The embodiments described above are merely some preferred embodiments of the present invention, and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for the harmless disposal and recycling of waste expanded polystyrene material containing fatty brominated flame-retardant components, characterized in that, Includes the following steps: The first step involves pulverizing waste expanded polystyrene material containing aliphatic brominated flame retardant components, dissolving the pulverized material in an organic solvent to obtain an organic solution containing expanded polystyrene. The aliphatic brominated flame retardant component is one or more of hexabromocyclododecane, octabromoether, methyl octabromoether, and brominated styrene-butadiene-styrene block copolymer. The organic solvent is composed of one or more of toluene, xylene, benzene, chlorobenzene, chloroform, dichloromethane, dichloroethane, acetonitrile, and tetrahydrofuran. The mass of the organic solvent is 0.5-100 times that of the pulverized material. The second step is to filter the polystyrene organic solution obtained in the first step to remove the solid insoluble matter. The third step involves adding a phase transfer catalyst to the filtered polystyrene organic solution. After stirring for a period of time, an alkaline solution or solid alkali is added. Subsequently, under the catalytic action of the phase transfer catalyst, the system temperature is maintained and stirring continues for a period of time to debrominate the bromine-containing flame-retardant components in the polystyrene organic solution. The phase transfer catalyst is a quaternary ammonium salt or tertiary ammonium salt compound, composed of one or more of tetramethylammonium bromide, tetramethylammonium chloride, tetraethylammonium bromide, tetraethylammonium chloride, tetrapropylammonium bromide, tetrapropylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, and triethylamine. The amount of the phase transfer catalyst used is 0.1%-5% of the mass of the waste expanded polystyrene material containing aliphatic bromine flame-retardant components. Fourth step: Add water to the polystyrene organic solution obtained in the third step, maintain the system temperature, stir and wash, and after standing, separate the organic phase and the aqueous phase. The organic phase yields a purified polystyrene organic solution, and the aqueous phase yields an aqueous solution containing bromide and alkali. The fifth step involves distilling the purified polystyrene organic solution under reduced pressure or normal pressure, or adding it to hot water to remove the organic solvent. The polystyrene-based material after solvent removal is then granulated, cooled, and dried to obtain recycled polystyrene granules. The sixth step involves neutralizing the aqueous solution containing bromide and alkali with acid and alkali, and then extracting the bromine component.

2. The method according to claim 1, characterized in that, The alkali in the alkaline solution described in the third step is composed of one or more of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, and ammonia water; the solid alkali is composed of one or more of sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide; the amount of alkali or the solid alkali used in the alkaline solution is 0.1%-10% of the mass of the polystyrene organic solution.

3. The method according to claim 1, characterized in that, The third step involves maintaining the system temperature between 0℃ and 100℃, with two stirring times of 0.1-24h each.

4. The method according to claim 1, characterized in that, The mass of water mentioned in step four is 1%-100% of the mass of the polystyrene organic solution.

5. The method according to claim 1, characterized in that, The fourth step, which involves maintaining the system temperature, means keeping the system temperature between 0°C and 100°C.

6. The method according to claim 1, characterized in that, The reduced pressure or atmospheric pressure distillation temperature mentioned in step 5 is 50-120℃; the hot water temperature is 60-100℃.

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