KR102548986B1 - A Recycling Method of Plasticizer - Google Patents

Abstract

The present invention relates to a method for recovering liquid paraffin, which is a plasticizer, from a waste solution discarded in a process of manufacturing a crosslinked polymer film using liquid paraffin as a plasticizer. The method can be separated from liquid paraffin in a simple way by gelating the silane-based monomer for cross-linking with water by hydrolysis and dehydration condensation polymerization.

Description

Recycling Method of Plasticizer {A Recycling Method of Plasticizer}

The present invention relates to a method for recovering liquid paraffin from a waste solution after plasticizer extraction in a wet polymer film manufacturing process produced by a crosslinking method.

As one of the methods for producing a porous polymer film in which a plurality of pores are formed, a wet polymer film manufacturing process is known in which a plasticizer such as liquid paraffin is injected into a polymer resin to form a film, and pores are formed by extracting the plasticizer using a solvent. In addition, as a method for improving physical properties such as penetration strength, a method of crosslinking by further introducing a crosslinking monomer such as a silane compound is used when manufacturing a polymer film.

However, when a polymer film is formed by such a crosslinking method, the waste solution generated after extracting the plasticizer with a solvent contains a solvent, a reaction initiator, a crosslinking monomer, a catalyst, and the like in addition to the plasticizer. Here, the initiator loses its reactivity after the extrusion process of the film and remains in the waste solution without any problem, and the catalyst has a very high boiling point compared to other components, so it can be easily separated by fractional distillation or the like. In addition, since very small amounts of initiator and catalyst are used, there is no problem even if they remain. However, since liquid paraffin, which is mainly used as a crosslinking monomer and a plasticizer, has a similar boiling point, it is difficult to separate by fractional distillation.

The present invention provides a plasticizer recovery method capable of separating a plasticizer such as liquid paraffin from a waste solution generated during the manufacture of a polymer film with high purity. Meanwhile, it will be readily appreciated that the objects and advantages of the present invention can be realized by means or methods described in the claims, and combinations thereof.

The present invention is to solve the above technical problem, and provides a method for recovering a plasticizer.

A first aspect of the present invention relates to the above method, the method comprising the following steps S1) to S3):

S1) removing the low boiling point solvent from the waste solution;

S2) mixing water (H ₂ O) with the product of (S1) from which the low boiling point solvent is removed; and

S3) filtering the product of (S2).

Here, the waste solution includes a low boiling point solvent, a plasticizer and a silane-based monomer, the plasticizer includes liquid paraffin, the boiling point of the low boiling point solvent is lower than the boiling point of the plasticizer, and the removal of the low boiling point solvent in step S1) The method of fractional distillation is used.

In a second aspect of the present invention, according to the first aspect, the silane-based monomer includes an alkoxy silane, an alkenyl alkoxy silane, or two or more thereof.

A third aspect of the present invention according to the first or second aspect, wherein the silane-based monomer is vinyltrimethoxysilane (VTMS), allyltrimethoxysilane (ATMS), 7-octenyltrimethoxysilane (OTMS) ), tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, trimethoxy Silane, triethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, isobutyltriethoxysilane, cyclo Hexyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane allyltriethoxysilane, dimethyldimethoxysilane, dimethyl diethoxysilane , diphenyldimethoxysilane, diphenyldiethoxysilane (bicyclo[2.2.1]hept-5-en-2-yl)trimethoxysilane ((Bicyclo[2.2.1]hept-5-en-2- yl)trimethoxysilane, BCHTMS), vinyltriethoxysilane (VTES), allyltriethoxysilane (ATES), 5-hexenyltriethoxysilane (HTES), 7-octenyltriethoxysilane (OTES), ( Bicyclo[2.2.1]hept-5-en-2-yl)triethoxysilane ((Bicyclo[2.2.1]hept-5-en-2-yl)triethoxysilane (BCHTES) or containing two or more of these do.

In the fourth aspect of the present invention, according to at least one of the first to third aspects, a pretreatment step of lowering the concentration of the low boiling point solvent in the waste solution to 3% by weight or less before performing the step (S1) is further performed will be.

In a fifth aspect of the present invention, in at least one of the first to fourth aspects, the addition of the water (H ₂ O) in the step (S2) is performed by spraying.

In the sixth aspect of the present invention, in the fifth aspect, the step (S2) is performed under conditions in which the product of (S1) is stirred.

In the seventh aspect of the present invention, in at least one of the first to sixth aspects, the low boiling point solvent includes methylene chloride.

In the eighth aspect of the present invention, in at least one of the first to seventh aspects, the step (S3) is performed by centrifugation.

In the ninth aspect of the present invention, in at least one of the first to eighth aspects, the concentration of the plasticizer in the product of the step (S3) is 90% by weight or more.

In the tenth aspect of the present invention, in at least one of the first to ninth aspects, the value of the following (Equation 1) is 15% or less:

(Formula 1) FTIR measured peak intensity of the silane monomer in the plasticizer recovered after step (S3) / FTIR measured peak intensity of the silane monomer in the waste solution before performing (S1)) X 100.

The method according to the present invention can recover the plasticizer by a simple method of hydrolyzing and polycondensing the crosslinking monomer. In addition, the plasticizer (liquid paraffin) recovered by the method according to the present invention has a very low content of impurities such as crosslinking monomers and a high purity of 90% by weight or more.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the present invention serve to further understand the technical idea of the present invention, the present invention is the details described in such drawings should not be construed as limited to On the other hand, the shape, size, scale or ratio of elements in the drawings included in this specification may be exaggerated to emphasize a clearer explanation.
1 is a schematic diagram showing a recovery device and a recovery method using the same according to a specific embodiment of the present invention.
Figure 2 shows a photographic image of a mixture of water and waste solution from which methylene chloride is removed in Example 1.
Figure 3 shows a photographic image of the gelled silane compound remaining on the filter net as a result of filtering the mixture of Figure 2.
Figure 4 shows a photographic image of liquid paraffin, which is a plasticizer recovered from the waste solution in Example 1.

The terms used in this specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventors can properly define the concept of terms in order to explain their invention in the best way. Based on the principle, it should be interpreted as a meaning and concept consistent with the technical idea of the present invention. Therefore, since the configurations shown in the embodiments described herein are only one of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention, various equivalents that can replace them at the time of this application It should be understood that there may be waters and variations.

Throughout the present specification, when a part is said to be "connected" to another part, this includes not only the case where it is "directly connected" but also the case where it is "electrically connected" with another element interposed therebetween. .

Throughout the present specification, when a part "includes" a certain component, it means that it may further include other components without excluding other components unless otherwise stated.

The terms "about," "substantially," and the like used throughout this specification are used in the sense of or close to a value when manufacturing and material tolerances inherent in the stated meaning are given, and are used accurately to aid in understanding the present application. or absolute numbers are used to prevent unfair use by unscrupulous infringers of the stated disclosure.

Throughout the present specification, the term "combination(s) thereof" included in the surface of the Markush form means one or more mixtures or combinations selected from the group consisting of the components described in the expression of the Markush form, It means including one or more selected from the group consisting of the above components.

Throughout the present specification, reference to "A and/or B" means "A or B or both".

As a polymer material for a separator that is generally used, polyolefin such as polyethylene, which is advantageous in forming pores, has excellent chemical resistance, mechanical properties, and electrical insulation properties, but is inexpensive, is mainly used. Polyethylene has low thermal properties and is prepared by cross-linking. As a method of cross-linking polyethylene, a method of introducing a silane-based monomer is mainly used. In addition, as a method of forming pores in a separation membrane, a method of injecting a plasticizer such as liquid paraffin into a polymer material to form a film and extracting the plasticizer using a solvent is mainly applied.

The present invention provides a method for recovering liquid paraffin used as a plasticizer from a waste solution generated in the manufacturing process of such a polyolefin-based porous film.

In one embodiment of the present invention, the method is S1) removing the low boiling point solvent from the waste solution, S2) mixing water (H ₂ O) with the product of S1) from which the low boiling point solvent is removed, and then S3) the above S2) Filtering the product of

First, the low boiling point solvent is removed from the waste solution by fractional distillation (S1).

As described above, the waste solution is generated in the process of manufacturing a polyolefin-based porous film, and includes a solvent used for extracting the plasticizer, a plasticizer used for pore formation, and a silane-based monomer used for the crosslinking reaction. can

In one embodiment of the present invention, the plasticizer is phthalic acid esters such as dibutyl phthalate, dihexyl phthalate, and dioctyl phthalate; aromatic ethers such as diphenyl ether and benzyl ether; fatty acids having 10 to 20 carbon atoms, such as palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid; fatty alcohols having 10 to 20 carbon atoms, such as palmitic acid alcohol, stearic acid alcohol, and oleic acid alcohol; Palmitic acid mono-, di-, or triesters, stearic acid mono-, di-, or triesters. Saturated and unsaturated fatty acids having 4 to 26 carbon atoms in the fatty acid group, such as oleic acid mono-, di-, or triesters, linoleic acid mono-, di-, or triesters, or one unsaturated fatty acid double bond substituted with an epoxy. or fatty acid esters in which two or more fatty acids are ester-bonded with an alcohol having 1 to 8 hydroxyl groups and 1 to 10 carbon atoms; etc., and one or more of them may be included. In the present invention, the plasticizer has a melting point of about -35°C to 0°C and a boiling point of about 180°C to 240°C, and is not limited to a particular type as long as it is used for forming pores in a polymer film. For example, paraffin having a melting point and a boiling point within the above ranges may be used as a plasticizer.

In addition, it is preferable to use a solvent having a low boiling point in order to be easily removed using a fractional distillation method in step S1). In particular, it is preferable that the boiling point of the solvent is lower than that of the plasticizer.

In one embodiment of the present invention, methylene chloride may be used as the low boiling point solvent, for example. Since the boiling point of the methylene chloride is about 40° C., it is very low compared to the boiling point of 180° C. to 240° C. of liquid paraffin, which is mainly used as a plasticizer. In this way, when a low-boiling solvent having a lower boiling point than that of the plasticizer is included, the step (S1) has the advantage of being easily processed using a method of fractional distillation. However, the low boiling point solvent is not particularly limited to methylene chloride, and any solvent having a lower boiling point than that of the plasticizer is possible. In addition, the low boiling point solvent may have a lower boiling point than that of the plasticizer as it can dissolve and elute the plasticizer from the sheet formed during the manufacture of the porous polymer sheet by a wet method.

Meanwhile, in one embodiment of the present invention, the waste solution is preferably further subjected to a pretreatment step of lowering the concentration of the low boiling point solvent to 3% by weight or less before performing step S1). The pretreatment step may use a method such as fractional distillation, and is not limited to a special method as long as the low boiling point solvent can be removed from the waste solution. Alternatively, methylene chloride may be removed from the waste solution by repeating the fractional distillation two or more times in step (S1). In the case of methylene chloride used in the manufacture of a polymer film, it is highly harmful to the human body and the environment, so it is preferable to recover the entire amount with high purity first and reuse it.

In one embodiment of the present invention, the concentration of the low boiling point solvent in the product obtained in the step (S1) is preferably 1% by weight or less.

Next, water (H ₂ O) is mixed with the product of S1) from which the low boiling point solvent is removed (S2). The product of step (S1) contains a plasticizer and a silane-based monomer, and by adding water thereto, hydrolysis and condensation polymerization of the silane-based monomer can be induced to gel them.

In one embodiment of the present invention, the silane-based monomer may be an alkoxy silane, an alkenyl alkoxy silane, etc., and specific examples thereof include vinyltrimethoxysilane (VTMS), vinyltriethoxysilane (VTES), vinyltriiso Propoxysilane (VTPS), Allyltrimethoxysilane (ATMS), 7-Octenyltrimethoxysilane (OTMS), Tetramethoxysilane, Tetraethoxysilane, Tetrapropoxysilane, Tetraisopropoxysilane, Tetramethoxysilane -n-butoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, trimethoxysilane, triethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane , ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, isobutyltriethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane, Vinyltriethoxysilane, allyltrimethoxysilane allyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane (bicyclo[2.2.1]hept-5- En-2-yl)trimethoxysilane ((Bicyclo[2.2.1]hept-5-en-2-yl)trimethoxysilane, BCHTMS), Vinyltriethoxysilane (VTES), Allyltriethoxysilane (ATES) , 5-Hexenyltriethoxysilane (HTES), 7-octenyltriethoxysilane (OTES), (bicyclo[2.2.1]hept-5-en-2-yl)triethoxysilane ((Bicyclo [2.2.1] hept-5-en-2-yl)triethoxysilane, BCHTES) and the like.

On the other hand, in one embodiment of the present invention, the addition of the water (H ₂ O) is preferably carried out in a spray method to increase the contact area between the water and the (S1) product, and the gelled silane In order to precipitate the compound and promote contact between the unreacted silane-based monomer and the sprayed water, the step of adding water (S1) may be performed under conditions in which the product is stirred.

Next, the product of the step (S2) is filtered to remove the gelled silane compound (S3). The filtration may be performed by selecting an appropriate pore such as a sieve or filter. In addition, together with or independently of this, the product of step (S2) can be centrifuged to separate the gelled silane compound, and as a result, the plasticizer can be recovered from the waste solution with high purity. In the present invention, the recovered plasticizer may exhibit a high purity of 90% or more. On the other hand, the concentration of the silane-based monomer in the recovered plasticizer can be confirmed through the peak intensity by FTIR analysis, which is a representative infrared spectroscopy method. In one embodiment of the present invention, the FTIR measurement peak intensity of the specific wavelength band of the silane-based monomer in the plasticizer recovered after step (S3) is the FTIR of the specific wavelength band of the silane-based monomer in the waste solution introduced in step (S1) It is less than 15% of the measured peak intensity. This can be expressed as (Equation 1) below.

(Equation 1) (FTIR measurement peak intensity of a specific wavelength range of the silane-based monomer in the recovered plasticizer / FTIR measurement peak intensity of a specific wavelength range of the silane-based monomer in the first waste solution) X 100

In one embodiment of the present invention, the peak intensity measured by FTIR in (Formula 1) can be confirmed by selecting a specific wavelength band that can represent the silane-based monomer contained in the waste solution and substituting the peak intensity found in the wavelength band there is. In one embodiment of the present invention, when the silane-based monomer is a silane having an alkoxy group, the wavelength of the alkoxy group of each silane-based monomer can be used as a representative wavelength. For example, in the case of VTMS in the waste solution, the concentration can be confirmed by substituting the peak intensity in the wavelength range of 1,090 cm ^-1 into the above formula (Equation 1). In addition, in the case of vinyltriethoxysilane (VTES), at least one peak intensity among peak intensities found at wavelengths of 1100 cm ^-1 and 1075 cm ^-1 may be substituted into (Equation 1). In addition, in the case of VTPS, the peak intensity of 1040 cm ⁻¹ may be substituted into the above (Equation 1). In this way, the 'specific wavelength range of the silane-based monomer' in the above (Formula 1) may be appropriately selected according to the specific chemical structure represented by each silane-based monomer used. In addition, selection of such a specific wavelength range is apparent to those skilled in the art.

If the peak intensity measured by FTIR in the plasticizer recovered after step (S3) exceeds 15% compared to the measurement result in the first waste solution, the recovered plasticizer is moved back to step (S2) and the process steps are repeated. can

Meanwhile, the plasticizer recovery method may be performed as a continuous process through the plasticizer recovery device 10 including the distillation device 100, the water mixing device 200, and the filtering device 300. Each of the above devices may be sequentially connected through pipes. 1 is a schematic diagram showing a plasticizer recovery device and a continuous process therethrough according to an embodiment of the present invention. Next, with reference to FIG. 1, the device and continuous process will be described in detail.

First, the waste solution generated after manufacturing the polymer film is introduced into the distillation apparatus 100 . It is preferable that the distillation device is provided with a heating device (not shown) and a temperature control device (not shown) so that the low boiling point solvent can be distilled by heating the waste solution. In addition, a pipe 110 is provided at the upper end of the distillation apparatus so that the vapor of the vaporized low-boiling point solvent can be discharged, and a discharge pump 120 can be provided to facilitate its discharge. The introduced waste solution is heated by the heating device, and when the temperature of the waste solution is raised above the boiling point of the low boiling point solvent, the low boiling point solvent is vaporized and its vapor is discharged to the outside of the distillation device through the pipe. In one embodiment of the present invention, the heating temperature is preferably adjusted to be maintained above the boiling point of the low boiling point solvent and below the boiling point of the plasticizer and the silane-based monomer. After the low boiling point solvent is removed, the waste solution remaining in the distillation device is then transferred to the water mixing device 200. The concentration of the low boiling point solvent in the remaining waste solution is preferably 1% or less. If the concentration exceeds 1%, step (S1) may be repeated one or more times before performing the next step.

Next, the water mixing device 200 mixes the waste solution transported from the distillation device 100 with water. In one embodiment of the present invention, the water mixing device 200 is provided with a watering device 210 at the top so that water can be evenly sprayed on the surface of the waste solution. On the other hand, the water mixing device may be provided with a stirring device 220 at the bottom to facilitate mixing of the sprayed water and the waste solution. As a result of mixing the waste solution and water in the water mixing device, the silane-based monomer in the waste solution is gelated by reaction with water. Next, the waste solution mixed with water is transferred to the filtration device 300. The filtering device is provided with a filtering net 310 through which the gelled silane-based monomer and plasticizer in the waste solution are separated. The filter net is not particularly limited in structure or shape as long as it has pores of an appropriate size, such as a sieve or filter, and can filter out gelled silane-based monomers in the waste solution. Meanwhile, in the present invention, the device may further include a centrifugal separator to centrifugate the plasticizer recovered from the filtration device 300 to remove residual silane-based monomers that may be included in the plasticizer.

Meanwhile, a step of confirming the concentration of the silane-based monomer through FTIR measurement for the finally recovered plasticizer may be further performed. As described above, this concentration measurement is that the IR peak intensity at a specific wavelength of the silane-based monomer contained in the finally recovered plasticizer is 15% or less compared to the FTIR peak intensity in the waste solution flowing into the distillation apparatus. If the FTIR peak intensity of the recovered plasticizer exceeds 15% compared to the measurement result in the first waste solution, the recovered plasticizer may be transferred to the water mixing device again and the process steps may be repeated.

Next, examples will be described in detail to aid understanding of the present invention. However, the embodiments according to the present invention can be modified in many different forms, and the scope of the present invention is not to be construed as being limited to the following examples. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example 1

After preparing the polymer film, a waste solution sample (sample A) was prepared. The waste solution contained methylene chloride (methyl chloride), vinyltrimethoxysilane and liquid paraffin. The waste solution was heated to 70 °C to remove methylene chloride (methyl chloride) through a method of fractional distillation. The waste solution from which methylene chloride was removed contained 99.5% of liquid paraffin and 0.5% of vinyltrimethoxysilane (weight ratio). 200 g of the above waste solution was sprayed with 20 g of water and mixed with the waste solution to gelate vinyltrimethoxysilane in the waste solution. 2 is a photographic image of a waste solution containing a gelled silane compound. Next, this was filtered using a 300 mesh filter net to remove the gelled silane compound. 3 is a photographic image of the filtered waste solution. Next, the waste solution was put into a centrifuge and centrifuged for 10 minutes to remove vinyltrimethoxysilane, a monomer remaining in the waste solution. Figure 4 is a photographic image of the plasticizer recovered after centrifugation. Finally, the concentration of vinyltrimethoxysilane present in the separated liquid paraffin was quantified through FTIR analysis, and the intensity of the peak compared to the initial peak was reduced to 8% based on a peak of 1,090 cm ^-1 .

Example 2

A waste solution sample (sample B) generated after the polymer film was prepared was prepared. The waste solution contained methylene chloride (methyl chloride), vinyltriethoxysilane (VTES) and liquid paraffin. The waste solution was heated to 70 °C to remove methylene chloride (methyl chloride) through a method of fractional distillation. The waste solution from which methylene chloride was removed contained 99.5% of liquid paraffin and 0.5% of vinyltriethoxysilane (weight ratio). 200 g of the above waste solution was sprayed with 20 g of water and mixed with the waste solution to gelate vinyltriethoxysilane in the waste solution. Next, this was filtered using a 300 mesh filter net to remove the gelled silane compound. Next, the waste solution was put into a centrifuge and centrifuged for 10 minutes to remove vinyltriethoxysilane, a monomer remaining in the waste solution. Finally, the concentration of vinyltriethoxysilane present in the separated liquid paraffin was quantified through FTIR analysis, and the intensity of the peak compared to the initial peak was reduced to 10% based on a peak of 1,075 cm ^-1 .

Claims (10)

(S1) removing the low boiling point solvent from the waste solution;
(S2) mixing water (H ₂ O) with the product of (S1) from which the low boiling point solvent is removed; and
(S3) filtering the result of (S2); including,
The waste solution contains a low boiling point solvent, a plasticizer and a silane-based monomer,
The plasticizer includes liquid paraffin,
The boiling point of the low boiling point solvent is lower than the boiling point of the plasticizer,
The removal of the low boiling point solvent in the step (S1) uses a method of fractional distillation,
A method for recovering plasticizers.
According to claim 1,
Wherein the silane-based monomer comprises an alkoxy silane, an alkenyl alkoxy silane or two or more of them.
According to claim 1,
The silane-based monomer is vinyltrimethoxysilane (VTMS), allyltrimethoxysilane (ATMS), 7-octenyltrimethoxysilane (OTMS), tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, trimethoxysilane, triethoxysilane, methyltrimethoxysilane, methyltriethoxy Silane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, isobutyltriethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane , vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane allyltriethoxysilane, dimethyldimethoxysilane, dimethyl diethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane (bicyclo[2.2 .1]hept-5-en-2-yl)trimethoxysilane ((Bicyclo[2.2.1]hept-5-en-2-yl)trimethoxysilane, BCHTMS), vinyltriethoxysilane (VTES), allyl Triethoxysilane (ATES), 5-hexenyltriethoxysilane (HTES), 7-octenyltriethoxysilane (OTES), (bicyclo[2.2.1]hept-5-en-2-yl) A method for recovering a plasticizer comprising triethoxysilane ((Bicyclo[2.2.1]hept-5-en-2-yl)triethoxysilane, BCHTES) or two or more of them.
According to claim 1,
A method for recovering a plasticizer, wherein a pretreatment step of lowering the concentration of the low-boiling solvent in the waste solution to 3% by weight or less before performing the step (S1) is further performed.
According to claim 1,
In the step (S2), the addition of the water (H ₂ O) is performed in a spray method.
According to claim 5,
The step (S2) is a plasticizer recovery method that is performed under conditions in which the resultant (S1) is stirred.
According to claim 1,
The low-boiling solvent is a plasticizer recovery method comprising methylene chloride (Methylene chloride).
According to claim 1
Wherein the (S3) step is carried out by centrifugation, a plasticizer recovery method.
According to claim 1,
The method for recovering plasticizers in which the concentration of the plasticizer in the product of step (S3) is 90% by weight or more.
According to claim 1,
A method for recovering a plasticizer having a value of 15% or less of the following formula (1):
(Equation 1) (FTIR measured peak intensity of silane monomer in plasticizer recovered after step (S3) / FTIR measured peak intensity of silane monomer in waste solution before performing (S1)) X 100.

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