KR102425240B1 - Eco-friendly Recycling Method of Waste Polystyrene - Google Patents

Abstract

The present invention relates to a recycling method of waste polystyrene, and more particularly, by dissolving and precipitating waste polystyrene using an eco-friendly solvent and water, and then performing foaming without the use of an additional blowing agent, thereby preventing environmental pollution and reducing polystyrene itself. The present invention relates to a method for recycling waste polystyrene that can be recycled into high-quality polystyrene without changing physical properties, and can be industrially usefully treated and regenerated polystyrene because of a high solvent recovery rate.

Description

Eco-friendly Recycling Method of Waste Polystyrene

The present invention relates to an eco-friendly recycling method of waste polystyrene, and more particularly, by recycling waste polystyrene using an eco-friendly solvent and water, while preventing environmental pollution and fire, and without changing the physical properties of polystyrene itself, It relates to a method or process for recycling waste polystyrene that can be recycled into high-quality polystyrene.

Polystyrene is a high molecular compound made by synthesizing ethylbenzene from benzene and ethylene and polymerizing dehydrogenation. It is used for various purposes, from containers to exteriors of home appliances. It is also widely used as expanded polystyrene by foaming it, which is a foamable plastic product in which hydrocarbon gas such as pentane or butane is injected into polystyrene resin and inflated with steam. Better known as 'Styropor', it is widely used as a packaging material, insulation material, cushioning material, and soundproofing material in each industrial field.

With the recent development of industry, more than several thousand tons of waste polystyrene is generated annually in Korea alone, and about half of these are recycled, but the other half is landfilled or incinerated, causing various environmental problems. .

Therefore, efforts to increase the recycling rate of waste polystyrene have been attempted in various ways, but the recovery rate is not yet high. In particular, since waste expanded polystyrene has a very large volume and it is difficult to collect and transport it, it is difficult to reduce the volume of waste expanded polystyrene and improve recycling efficiency. are being developed in various ways.

As a typical solution reduction method, a method of melting waste expanded polystyrene using a chemical as a solvent, and a method of reducing the volume physically by extrusion by applying heat to the waste expanded polystyrene are used.

As an example, Korean Patent Application Laid-Open No. 2000-59032 discloses a method for reducing the volume of waste expanded polystyrene by heating and melting it. This reduction method produces a strong odor due to the generation of gas by heating, pollutes the atmosphere by toxic gas generated during heating, and continuously heats and extrudes the heat of fusion, increasing the cost of energy use by continuous heating. , the physical properties of the resin reduced by heat deteriorated, and it was not easy to remove foreign substances attached to the waste expanded polystyrene, so there was a problem in that it was impossible to use waste polystyrene in a state in which foreign substances were fixed, such as waste materials for construction or rich people in fishing villages. .

In addition, Korea Utility Model Registration No. 20-21594 discloses a method of compressing and reducing waste expanded polystyrene by mechanical means, but this method has low reduction efficiency due to the strong characteristics of expanded polystyrene material and consumes a lot of energy. There was a problem with consumption.

And, the method for reducing the volume using a solvent, which is a chemical, is to liquefy the waste expanded polystyrene using a solution such as toluene, acetone, or methyl chloride to melt, and to precipitate the liquefied material using alcohol such as methanol, heating method Although the generation of toxic gas is prevented, the solvent and precipitant itself are harmful substances, and the risk of fire is high due to the flammability of petroleum solutions, as well as environmental pollution due to evaporation of solvents, loss of solvents, and reduction of use Later, there was a problem in that the physical properties of the waste expanded polystyrene were changed due to the extraction of the solvent, so that the range of use according to recycling was reduced.

Accordingly, in Korean Patent Laid-Open No. 2003-0032486, distilled water was mixed with a petroleum solution to reduce the risk of fire, but the use of a solvent, which is a toxic substance, limits reuse due to the toxicity of the solvent and changes in physical properties by extraction. there was a problem with

Korean Patent Publication No. 2000-59032 (published date: 10.05.2000) Korea Patent Publication No. 2003-003248 (published on: April 26, 2003)

The main object of the present invention is to solve the above problems, and it is possible to fundamentally block the generation of harmful gases, etc. in the workplace, and at the same time prevent the occurrence of a fire and at the same time do not change the physical properties of polystyrene itself, and regenerate it into high-quality polystyrene An object of the present invention is to provide a recycling method of waste polystyrene that can be industrially usefully treated with a high recovery rate of a solvent and a precipitant, and can regenerate polystyrene into a foam shape.

In order to achieve the above object, one embodiment of the present invention comprises the steps of: (a) adding methyltetrahydrofuran to waste polystyrene to obtain a mixture in which polystyrene is dissolved; (b) adding water to the polystyrene-dissolved mixture to obtain a polystyrene-precipitated precipitate; and (c) separating the polystyrene from the mixture by filtering the precipitate.

The mass ratio of waste polystyrene: methyltetrahydrofuran: water in the total sum of the masses of waste polystyrene, methyltetrahydrofuran and water in step (b) is 5 wt% to 20 wt%: 5 wt% to 30 wt%: 50 wt% to 90wt%, in the section where the content of waste polystyrene is 5 wt% or more and less than 7 wt%, the mass ratio of methyltetrahydrofuran/water is 0.05 to 0.30, and in the section where the content of waste polystyrene exceeds 7wt% and less than 10wt%, methyltetrahydrofuran/ The mass ratio of water is 0.10 to 0.32, and in the section where the content of waste polystyrene exceeds 10 wt% and less than 15 wt%, the mass ratio of methyltetrahydrofuran/water is 0.15 to 0.44, and the content of waste polystyrene exceeds 15 wt% and less than 20 wt% in the section It can be characterized in that the mass ratio of methyltetrahydrofuran/water is in the range of 0.26 to 0.50.

In a preferred embodiment of the present invention, the method for recycling waste polystyrene further comprises recovering methyltetrahydrofuran and water by distilling the filtrate from which polystyrene is separated in step (c) after step (c), respectively. It may be characterized in that, the distillation may be characterized in that it is carried out at 50 ℃ ~ 80 ℃.

In a preferred embodiment of the present invention, the method for recycling waste polystyrene may further include vacuum foaming the polystyrene precipitate separated in step (c) to obtain polystyrene, wherein the vacuum foaming is 0.0 It may be characterized in that it is carried out at 80 ℃ ~ 120 ℃ under a pressure of MPa ~ 0.1 MPa.

In a preferred embodiment of the present invention, the steps (a) and (b) may be characterized in that they are performed at room temperature and under normal pressure.

Another embodiment of the present invention, (i) adding a solvent selected from the group consisting of tetrahydrofuran, methyltetrahydrofuran and mixtures thereof to waste polystyrene to obtain a polystyrene dissolved mixture; (ii) adding water to the polystyrene-dissolved mixture to obtain a polystyrene-precipitated precipitate; (iii) filtering the precipitate to separate polystyrene from the mixture; and (iv) vacuum foaming the polystyrene precipitate separated in step (iii) to obtain polystyrene.

In another preferred embodiment of the present invention, the solvent is tetrahydrofuran, and the mass ratio of waste polystyrene: tetrahydrofuran: water in the total sum of the masses of waste polystyrene, tetrahydrofuran, and water in step (ii) is 5 to 30 wt% : 5 to 40 wt%: 35 to 90 wt%, and the mass ratio of tetrahydrofuran/water in the section where the ratio of waste polystyrene is 5 wt% or more and 7 wt% or less is 0.05 to 0.33, and 0.10 to 0.55 in the section exceeding 7 wt% and less than 10 wt% is 0.15 to 0.78 in the section exceeding 10 wt% and less than or equal to 15 wt%, 0.26 to 1.0 in the section exceeding 15 wt% and less than or equal to 20 wt%, and 0.45 to 1.05 in the section exceeding 20 wt% and less than or equal to 25 wt%, and 0.70 in the section exceeding 25 wt% and less than or equal to 30 wt% It may be in the range of ~ 1.25.

In another preferred embodiment of the present invention, the solvent is methyltetrahydrofuran, and the mass ratio of waste polystyrene: methyltetrahydrofuran: water in the total sum of the masses of waste polystyrene, methyltetrahydrofuran and water in step (ii) is 5 ~ 20 wt%: 5 ~ 30 wt%: 50 ~ 90 wt%, in the section where the content of waste polystyrene is 5 wt% or more and less than 7 wt%, the mass ratio of methyltetrahydrofuran/water is 0.05 to 0.30, and the content of waste polystyrene is 7 The mass ratio of methyltetrahydrofuran/water is 0.10 to 0.32 in the section exceeding 10 wt% and less than 10 wt%, and the mass ratio of methyltetrahydrofuran/water is 0.15 to 0.44 in the section in which the content of waste polystyrene exceeds 10 wt% and less than or equal to 15 wt%, In the section where the content of waste polystyrene exceeds 15 wt% and less than 20 wt%, it may be characterized in that the mass ratio of methyltetrahydrofuran/water is 0.26 to 0.50.

In another preferred embodiment of the present invention, the vacuum foaming of step (iv) may be characterized in that it is performed at 80 °C to 120 °C under a pressure of 0.0 MPa to 0.1 MPa.

In another preferred embodiment of the present invention, the method for recycling waste polystyrene further comprises recovering a solvent and water by distilling the filtrate from which polystyrene is separated in step (iii) after step (iii), respectively. It can be, and the distillation may be characterized in that it is carried out at 50 ℃ ~ 80 ℃.

In another preferred embodiment of the present invention, the steps (i) and (ii) may be characterized in that they are performed at room temperature and under normal pressure.

According to the present invention, by regenerating waste polystyrene using an eco-friendly solvent and water, it is possible to prevent environmental pollution caused by the use of toxic organic solvents, and at the same time, without changing the physical properties of polystyrene itself, it can be regenerated into high-quality polystyrene, solvent And since the recovery rate of water is high, there is an effect of industrially usefully treating waste polystyrene, and regenerating polystyrene into a foam shape.

1 is a schematic process diagram showing a method for recycling waste polystyrene according to an embodiment of the present invention.
2 is a schematic process diagram showing a recycling method of waste polystyrene according to another embodiment of the present invention.
3 is a photograph taken of the precipitates obtained in Examples and Comparative Examples of the present invention, (a) is the precipitate of Comparative Example 5, (b) is the precipitate of Example 4, (c) is Example 1 of the precipitate, and (d) is the precipitate of Example 5.
4 is a graph of the GPC measurement result of polystyrene regenerated in an embodiment of the present invention.
5 is a graph showing the results of thermogravimetric analysis of polystyrene regenerated in Example 1 of the present invention.
6 is a graph showing the result of the volume expansion rate according to the foaming pressure of the polystyrene regenerated in Example 1 of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is those well known and commonly used in the art.

In the present specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

As used herein, 'waste polystyrene' includes all polystyrene discarded after being used in various industrial fields, and may be applied regardless of their shape, use, and the like.

As used herein, 'room temperature' is the normal atmospheric temperature and may be 20 ± 10 °C, and 'normal pressure' means normal atmospheric pressure.

As used herein, terms such as “comprises”, “comprises” or “has” refer to the presence of, and refer to, a feature, number, step, action, component, part, or combination thereof described in the specification. It does not exclude the possibility that other features, figures, steps, acts, components, parts, or combinations thereof may exist or may be added, unless otherwise noted.

In one aspect, the present invention comprises the steps of: (a) adding methyltetrahydrofuran to waste polystyrene to obtain a mixture in which polystyrene is dissolved; (b) adding water to the polystyrene-dissolved mixture to obtain a polystyrene-precipitated precipitate; and (c) separating the polystyrene from the mixture by filtering the precipitate.

More specifically, in the recycling method of waste polystyrene according to an embodiment of the present invention, waste polystyrene is dissolved using methyltetrahydrofuran, an eco-friendly solvent derived from biomass, and then precipitated using water during precipitation. It is free from environmental pollution problems and can be regenerated into high-quality polystyrene without changing the physical properties of polystyrene itself, and the recovery rate of methyltetrahydrofuran and water is high, so waste polystyrene can be effectively treated industrially.

Hereinafter, a preferred embodiment of a method for recycling waste polystyrene according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic process diagram illustrating a method for recycling waste polystyrene according to an embodiment of the present invention, and FIG. 2 is a schematic process diagram illustrating a method for recycling waste polystyrene according to another embodiment of the present invention.

Referring to FIG. 1 , in the method of recycling waste polystyrene according to an embodiment of the present invention, methyltetrahydrofuran is first added to waste polystyrene at room temperature and under normal pressure, and stirred to obtain a polystyrene-dissolved mixture [step (a)) ].

In the present invention, the methyltetrahydrofuran (methyltetrahydrofuran) is used as a solvent for dissolving waste polystyrene.

The methyltetrahydrofuran has a Hildebrand Solubility parameter (HSP) of 16.9 MPa ^1/2 , which has high solubility in polystyrene, but has low solubility in other synthetic resins such as polypropylene and polyethylene, and does not ignite and vaporize at the same time It has a high point and is very eco-friendly as it is manufactured from biomass. In addition, tetrahydrofuran, toluene, etc. may be used as solvents for polystyrene, but these are highly toxic to the human body, so there may be problems from an environmental point of view. In addition, tetrahydrofuran has a high volatilization rate, which may adversely affect the environment in the workplace when treating sediments, and has a problem that it is not easy to separate due to its high compatibility with a precipitant in the future. In spite of this low level, the precipitation of dissolved polystyrene hardly occurs even when an excessive amount of the precipitating agent is used. On the other hand, methyltetrahydrofuran is an eco-friendly material derived from biomass, and has low volatility and solubility in water as a precipitant, making it easy to separate and recover the solvent after use.

Therefore, in the present invention, by dissolving waste polystyrene using methyltetrahydrofuran, polystyrene can be completely dissolved in a short time even at room temperature and normal pressure, thereby improving the water volume reduction efficiency. Contamination, loss of solvent, etc. can be prevented, and the easiness of a work process such as solvent recovery can be improved.

As such, the mixture to which methyltetrahydrofuran is added may be stirred at room temperature and atmospheric pressure so that waste polystyrene is dissolved. At this time, when the waste polystyrene is completely dissolved in the solvent, it is temporarily left to settle foreign substances such as flame retardants, binders, and coating agents other than polystyrene contained in the waste polystyrene, and the sedimented foreign substances can be removed from the mixture by filtering.

On the other hand, in the recycling method of waste polystyrene according to an embodiment of the present invention, vinyl, paper, wood chips, food waste, small stones, etc. attached to waste polystyrene by washing the waste polystyrene before step (a), etc. The method may further include removing impurities from the waste polystyrene and pulverizing the waste polystyrene to a size suitable for dissolution.

In this case, the pulverized waste polystyrene may be pulverized to have an average particle size of 1.0 cm to 10 cm, which is a suitable size for dissolution.

Thereafter, the mixture in which waste polystyrene is dissolved is obtained by adding water at room temperature and under normal pressure to obtain a polystyrene precipitated precipitate [step (b)].

The water serves to precipitate only polystyrene in a mixture in which waste polystyrene is dissolved, and may be used without limitation as long as it is purified water.

In the present invention, by applying the water as a precipitant, it is harmless to the human body, environmentally friendly, and preferable in terms of price, as well as being easily separated from the solvent after recovery of polystyrene compared to conventional precipitants such as alcohol. There is an advantage.

The proportion of waste polystyrene in the total sum of the masses of waste polystyrene, methyltetrahydrofuran and water may be in the range of 5 wt% to 20 wt%. When the proportion of waste polystyrene is less than 5 wt%, excessive energy is used for recovery of the solvent and precipitant, and when it exceeds 20 wt%, the dissolution of waste polystyrene may be insufficient.

In addition, the ratio of the methyltetrahydrofuran may be 5 wt% to 30 wt%. If the proportion of methyltetrahydrofuran is less than 5 wt%, dissolution of waste polystyrene may be insufficient, and when it exceeds 30 wt%, precipitation of waste polystyrene may not occur even if water is added.

The proportion of the water may be 50 wt% to 90 wt%. If the proportion of water is less than 50 wt%, precipitation may not occur, and if it exceeds 90 wt%, excessive energy may be used for the recovery and separation of the solvent and the precipitant in the future.

The mass ratio of methyltetrahydrofuran/water in the section where the content of waste polystyrene is 5 wt% or more and 7 wt% or less is 0.05 to 0.35, and the mass ratio of methyltetrahydrofuran/water in the section where the content of waste polystyrene exceeds 7 wt% and less than 10 wt% is 0.10 to 0.32, and the mass ratio of methyltetrahydrofuran/water is 0.15 to 0.44 in the section where the content of waste polystyrene exceeds 10 wt% and 15 wt% or less, and the content of waste polystyrene exceeds 15 wt% and 20 wt% or less In the section, methyltetrahydrofuran/ The mass ratio of water may be in the range of 0.26 to 0.50. For precipitation according to the present invention, the smaller the ratio of waste polystyrene, the smaller the mass ratio of methyltetrahydrofuran/water is required for precipitation to occur.

As described above, when polystyrene is precipitated in a lysate in which polystyrene is dissolved by methyltetrahydrofuran by addition of water as described above, the precipitate is filtered to separate and recover polystyrene from a mixture containing methyltetrahydrofuran and water [(c) ) step].

The filtration may be applied without limitation as long as it is a method commonly applied in the art, and may preferably be a separatory funnel, a filter method, a shaker method, a centrifugal separation method, and the like.

Thereafter, when polystyrene is separated and recovered from the precipitate, the separated polystyrene is dried under normal pressure or vacuum to obtain a polystyrene ingot.

In addition, the mixture containing methyltetrahydrofuran and water remaining after the polystyrene is separated in step (c) may be distilled for reuse to separate and recover water and methyltetrahydrofuran.

The distillation may be performed at 50° C. to 80° C. under vacuum or atmospheric pressure using a conventional distiller.

In another aspect, the present invention provides a method comprising: (i) adding a solvent selected from the group consisting of tetrahydrofuran, methyltetrahydrofuran, and mixtures thereof to waste polystyrene to obtain a mixture in which polystyrene is dissolved; (ii) adding water to the polystyrene-dissolved mixture to obtain a polystyrene-precipitated precipitate; (iii) filtering the precipitate to separate polystyrene from the mixture; and (iv) vacuum foaming the polystyrene precipitate separated in step (iii) to obtain polystyrene.

More specifically, in the recycling method of waste polystyrene according to another embodiment of the present invention, after dissolving and precipitating waste polystyrene using a solvent and water containing tetrahydrofuran and/or methyltetrahydrofuran, respectively, an additional blowing agent is used. By vacuum foaming without use, it is possible to prevent environmental pollution and fire, and at the same time, without changing the physical properties of polystyrene itself, it can be regenerated into high-quality polystyrene, and the recovery rate of solvent is high, so waste polystyrene can be effectively treated industrially. . In addition, when polystyrene produced by regeneration is used again as polystyrene, it is possible to regenerate the polystyrene in the form of foam by directly foaming it in the regeneration step without using a separate foaming agent, so the process can be simplified, and in terms of cost. There are far more advantages.

Referring to FIG. 2 , in the method of recycling waste polystyrene according to another embodiment of the present invention, a solvent is first added to waste polystyrene at room temperature and under normal pressure and stirred to obtain a mixture in which polystyrene is dissolved [step (i)].

The solvent may be selected from the group consisting of tetrahydrofuran, methyltetrahydrofuran, and mixtures thereof.

In the above embodiment according to the present invention, the reduction and simultaneous foaming are performed in one process, and the recovery of the solvent, including the process, is made in the closed circulation system. Therefore, even when tetrahydrofuran is used as a solvent, it is possible to prevent environmental problems in the workplace and a decrease in solvent recovery rate due to solvent volatilization. There is an advantage that

Therefore, in the present invention, by dissolving and foaming waste polystyrene using tetrahydrofuran, methyltetrahydrofuran, and a mixture thereof, polystyrene is completely dissolved in a short time even at room temperature and normal pressure to improve the reduction efficiency. and foaming can be performed without an additional blowing agent, so that it can be regenerated into high-quality polystyrene foam.

The solvent-added mixture may be stirred at room temperature and pressure to completely dissolve waste polystyrene. At this time, when the waste polystyrene is completely dissolved in the solvent, it is temporarily left to settle foreign substances such as flame retardants, binders, and coating agents other than polystyrene contained in the waste polystyrene, and the sedimented foreign substances can be removed from the mixture by filtering.

On the other hand, in the recycling method of waste polystyrene according to another embodiment of the present invention, vinyl, paper, wood chips, food scraps, small stones, etc. attached to waste polystyrene by washing the waste polystyrene before step (i), etc. The method may further include removing impurities from the waste polystyrene and pulverizing the waste polystyrene to a size suitable for dissolution. In this case, the pulverized waste polystyrene may be pulverized to have an average particle size of 1.0 cm to 10 cm, which is a suitable size for dissolution.

Thereafter, the mixture in which the waste polystyrene is dissolved is added to water at room temperature and under normal pressure to obtain a precipitate in which polystyrene is precipitated [step (ii)].

The water serves to precipitate only polystyrene in a mixture in which waste polystyrene is dissolved, and may be used without limitation as long as it is purified water.

In the present invention, by applying the water as a precipitant, it is harmless to the human body, environmentally friendly, and preferable in terms of price, as well as a difference in vaporization point with the solvent after recovery of polystyrene compared to conventional precipitants such as alcohol. There is an advantage that can be easily separated and recovered from.

When the solvent in step (ii) is methyltetrahydrofuran, the mass ratio of waste polystyrene:methyltetrahydrofuran:water in step (ii) is 5 wt% to 20 wt%: 5 wt% to 30 wt% : It may be 50 wt% ~ 90 wt%.

The mass ratio of methyltetrahydrofuran/water in the section in which the content of the waste polystyrene is 5 wt% or more to 7 wt% or less is 0.05 to 0.30, and in the section more than 7 wt% to 10 wt% or less, 0.10 to 0.32, more than 10 wt% It may be in the range of 0.15 to 0.44 in the range of 15 wt% or less, and may be in the range of 0.26 to 0.50 in the range of more than 15 wt% and less than 20 wt%.

When the solvent is tetrahydrofuran in step (ii), the mass ratio of waste polystyrene: tetrahydrofuran: water in the total sum of the masses of waste polystyrene, tetrahydrofuran, and water is 5 wt% to 30 wt%: 5 wt% to 40 wt%: It may be 35 wt% to 90 wt%.

The mass ratio of tetrahydrofuran/water in the section where the content of the waste polystyrene is 5 wt% or more and 7 wt% or less is 0.05 to 0.33, and the mass ratio of tetrahydrofuran/water in the section where the content of the waste polystyrene exceeds 7 wt% and 10 wt% or less is 0.10 to 0.55, the mass ratio of tetrahydrofuran/water is 0.15 to 0.78 in the section in which the content of waste polystyrene exceeds 10 wt% and less than 15 wt%, and in the section where the content of waste polystyrene exceeds 15 wt% and less than 20 wt%, tetrahydrofuran The mass ratio of furan/water is 0.26 to 1.0, the mass ratio of tetrahydrofuran/water is 0.45 to 1.05 in the section where the content of waste polystyrene exceeds 20 wt% and less than 2 5 wt%, and the content of waste polystyrene exceeds 25 wt% and less than 30 wt% In the section, the mass ratio of tetrahydrofuran/water may be in the range of 0.70 to 1.25.

As described above, when polystyrene is precipitated in a melt in which polystyrene is dissolved by a solvent by the addition of water, the precipitate is filtered to separate polystyrene from the mixture containing the solvent and water [(iii) step].

The filtration may be applied without limitation as long as it is a method commonly applied in the art, and may preferably be a separatory funnel, a filter method, a shaker method, a centrifugal separation method, and the like.

Thereafter, the separated polystyrene precipitate is vacuum-foamed into separated polystyrene without addition of a blowing agent to obtain a foamed polystyrene foam [(iv) step].

The vacuum foaming is performed at 80 °C to 120 °C under a pressure of 0.0 MPa to 0.1 MPa using a conventional vacuum foaming device. Since it does not come out, a problem that foaming is not complete may occur.

In addition, when the temperature at the time of vacuum foaming is less than 80 ℃, it is lower than the glass transition temperature of polystyrene, so foaming is difficult to occur, and when it exceeds 120 ℃, the structure of the polystyrene collapses or vaporization occurs. There may be problems in that foaming does not occur or the recovery rate is lowered.

Meanwhile, it is possible to perform foaming after mixing necessary additives such as a flame retardant according to the intended use of the regenerated expanded polystyrene within the limit of not changing the physical properties of the expanded polystyrene in the polystyrene separated before vacuum foaming.

In the vacuum-foamed expanded polystyrene, the amount of residual solvent or precipitant is maintained at 1 wt % or less, so that material properties of expanded polystyrene, for example, properties such as tensile strength and heat resistance, can be maintained at optimum values even after regeneration.

When polystyrene is separated from the precipitate containing the solvent and water as described above, the solvent and water may be recovered by distilling the mixture of the solvent and water remaining after the polystyrene is separated for reuse.

The distillation may be carried out under normal pressure or vacuum using a conventional distiller, and preferably at 50°C to 80°C.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are only examples to help the understanding of the present invention, and the scope of the present invention is not limited thereto.

<Example 1>

5 g of the pulverized waste expanded polystyrene was put into a reactor that can be opened and closed at room temperature, 10 g of 2-methyltetrahydrofuran was added thereto, and stirred for 5 minutes to dissolve the waste expanded polystyrene. 30 g of water as a precipitant was added to the mixture in which the waste expanded polystyrene was dissolved to precipitate polystyrene, and the precipitated polystyrene was filtered using a separatory funnel. Thereafter, the filtered polystyrene was vacuum-foamed at 100° C. under a pressure of 0.05 MPa using a vacuum foaming device to regenerate the expanded polystyrene. In addition, a mixture of 2-methyltetrahydrofuran and water remaining after polystyrene was filtered was distilled to recover water and 2-methyltetrahydrofuran, respectively.

<Examples 2 to 5>

In the same manner as in Example 1, the waste expanded polystyrene was regenerated, and the solvent and the precipitant were respectively recovered, but the waste expanded polystyrene was regenerated under the conditions described in Table 1, and the solvent and the precipitant were respectively recovered.

<Comparative Examples 1 to 7>

In the same manner as in Example 1, the waste expanded polystyrene was regenerated, and the solvent and the precipitant were respectively recovered, but the waste expanded polystyrene was regenerated under the conditions described in Table 1, and the solvent and the precipitant were respectively recovered.

[Table 1]

<Experimental Example 1: Measurement of polystyrene precipitation and foaming>

Precipitation and foaming of the polystyrene obtained in Examples 1 to 5 and Comparative Examples 1 to 7 were measured, and the results are shown in Tables 2 and 3 below.

[Table 2]

As shown in Tables 2 and 3, in the case of Examples 1 to 5, polystyrene was precipitated and foamed, and the recovery rates of the solvent and the precipitant after foaming were 96%, respectively, whereas in Comparative Examples 1 to 7, Precipitation and foaming of polystyrene did not occur. In particular, when toluene was used as a solvent as in Comparative Examples 1 and 2, no precipitation occurred even with an excess of precipitating agent, and as in Comparative Example 5, the smaller the ratio of waste polystyrene compared to the precipitating agent, the more an excess of precipitating agent is required. could check

<Experimental Example 2: Measurement of physical properties of regenerated expanded polystyrene>

The polymer properties of the expanded polystyrene regenerated in Examples 1 and 3 and the polymer properties of the spent expanded polystyrene before regeneration, the column is HR 0.5, 1, 2, 3, 4, 4E, 5, 6 (THF), and the eluent (Eluent) is Tetrahydrofuran (THF), and the detector is an RI detector, GPC (Gel permeation chromatography, Waters Alliance e2695). The results are shown in FIG. 4 .

As shown in FIG. 4 , it was confirmed that the polymer properties of the expanded polystyrene polymer regenerated in Examples 1 and 3 and the waste polystyrene prior to regeneration were similar.

Accordingly, in the recycling method of waste polystyrene according to the present invention, waste polystyrene is dissolved and precipitated using tetrahydrofuran and/or methyltetrahydrofuran and water, and then foaming is performed without the use of an additional blowing agent, thereby reducing environmental pollution and fire. It was confirmed that high-quality expanded polystyrene can be regenerated without changing the physical properties of polystyrene itself.

<Experimental Example 3: Thermogravimetric measurement of regenerated expanded polystyrene>

Thermogravimetric analysis (TGA N-1000, SCINCO) of the filtered expanded styrene precipitate after precipitation in Example 1 was measured, and the measurement results are shown in FIG. 5 .

As shown in Fig. 5, the weight loss below 100 °C is due to the residual solvent, the weight loss above 100 °C is due to residual water, and the weight loss near 380 °C is due to the vaporization of polystyrene, It was confirmed that the precipitate obtained in Example 1 contained 20% of the solvent and water.

<Experimental Example 4: Measurement of the foaming effect according to the present invention>

In the foaming step of the polystyrene precipitate obtained after precipitation in Example 1, the volume expansion rate according to the foaming pressure of the polystyrene was measured while changing the foaming pressure, and the results are shown in FIG. 6 . At this time, the volume expansion rate was measured by the water displacement method.

As shown in FIG. 6 , it can be confirmed that sufficient foaming is achieved even by the foaming process according to the present invention.

Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and this is also the present invention. It is natural to fall within the scope of

Claims (10)

delete delete delete delete delete (i) adding a solvent selected from the group consisting of tetrahydrofuran, methyltetrahydrofuran, and mixtures thereof to waste expanded polystyrene to obtain a mixture in which waste expanded polystyrene is dissolved;
(ii) adding water to the mixture in which the waste expanded polystyrene is dissolved to obtain a polystyrene precipitated precipitate;
(iii) filtering the precipitate to separate polystyrene from the mixture; and
(iv) foaming the polystyrene precipitate separated in step (iii) at 80° C. to 120° C. under a pressure of 0.0 MPa to 0.1 MPa to obtain expanded polystyrene;
delete delete 7. The method of claim 6,
The solvent is tetrahydrofuran,
In the total sum of the masses of waste expanded polystyrene, tetrahydrofuran and water in step (ii), the mass ratio of waste expanded polystyrene: tetrahydrofuran: water is 5 wt% to 30 wt%: 5 wt% to 40 wt%: 35 wt% ~ 90wt%, the mass ratio of tetrahydrofuran/water in the section in which the content of waste expanded polystyrene is 5 wt% or more and 7 wt% or less is 0.05 to 0.33, and in the section where the content of waste expanded polystyrene exceeds 7 wt% and 10 wt% or less The mass ratio of tetrahydrofuran/water is 0.10 to 0.55, the mass ratio of tetrahydrofuran/water is 0.15 to 0.78 in the section where the content of waste expanded polystyrene exceeds 10 wt% and 15 wt% or less, and the content of waste expanded polystyrene exceeds 15 wt% In the section of 20 wt% or less, the mass ratio of tetrahydrofuran/water is 0.26 to 1.0, and in the section where the content of waste expanded polystyrene is more than 20 wt% and less than 25 wt%, the mass ratio of tetrahydrofuran/water is 0.45 to 1.05, In the section where the content is more than 25 wt% and less than 30 wt%, the mass ratio of tetrahydrofuran/water is 0.70 to 1.25.
7. The method of claim 6,
The solvent is methyltetrahydrofuran,
In the total sum of the mass of waste expanded polystyrene, methyltetrahydrofuran and water in step (ii), the mass ratio of waste expanded polystyrene: methyltetrahydrofuran: water is 5 wt% to 20 wt%: 5 wt% to 30 wt%: 50 It is wt% to 90 wt%, and in the section where the content of waste expanded polystyrene is 5 wt% or more and less than 7 wt%, the mass ratio of methyltetrahydrofuran/water is 0.05 to 0.30, and the content of waste expanded polystyrene exceeds 7 wt% and 10 wt% In the section below, the mass ratio of methyltetrahydrofuran/water is 0.10 to 0.32, and in the section where the content of waste expanded polystyrene exceeds 10 wt% and below 15 wt%, the mass ratio of methyltetrahydrofuran/water is 0.15 to 0.44, and the content of waste expanded polystyrene In this section of more than 15 wt% and less than 20 wt%, the mass ratio of methyltetrahydrofuran/water is 0.26 to 0.50.

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