Method for producing laurolactam, synthesis apparatus therefor, laurolactam composition produced thereby, and method for producing polylaurolactam using the same

Abstract

The present invention relates to a method for producing laurolactam, the method comprising the steps of: a) synthesizing laurolactam by Beckmann rearrangement of cyclododecanone oxime in the presence of a catalyst; b) mixing the laurolactam synthesized in step a) with a good solvent to remove the catalyst; and c) mixing the laurolactam from which the catalyst has been removed in step b) with an empty solvent to recrystallize it; an apparatus for the synthesis; a laurolactam composition produced thereby; and a method for producing polylaurolactam using the laurolactam composition.

Description

[Technical Field]

[0001] The present invention relates to a method for producing laurolactam, an apparatus for synthesizing the same, a laurolactam composition produced thereby, and a method for producing polylaurolactam using the same.

[0002] The present invention provides a new method for producing laurolactam that takes into consideration the drawback that a mixed catalyst of TCT (cyanuric chloride, trichlorotriazine) and ZnCl2, which has been used as a catalyst and co-catalyst in the conventional production of laurolactam, is difficult to remove from laurolactam. [Background technology]

[0003] Generally, cyclic amide monomers, such as laurolactam, are synthesized by Beckmann rearrangement of cyclododecanone oxime.

[0004] Such polyamide polymeric substances such as polylaurolactam can be synthesized by anionic polymerization, and the purity of the laurolactam monomer has a significant effect on the polymerization reaction activity, so the purity of the monomer is a very important factor in the polymerization reaction.

[0005] Laurolactam monomers produced by conventional Beckmann potential reaction are purified by distilling off the solvent after the reaction is complete, followed by Heavies removal in solid and / or liquid phases. However, this method still leaves traces of catalyst remaining in the final laurolactam product, which rapidly reduces the activity of the anionic polymerization reaction.

[0006] Therefore, there is a demand for a method for easily removing the catalyst remaining after the Beckmann potential reaction to purify high-purity laurolactam and to enhance the anionic polymerization activity of laurolactam monomers and the like.

[0007] One such method, filed by the applicant in 2019-161182, involves synthesizing cyclododecanone oxime into laurolactam through a Beckmann rearrangement in the presence of TCT and ZnCl2 catalysts, then adding a good solvent such as ethanol to remove the catalyst, and then adding a poor solvent such as water to recrystallize the product, recovering the monomer from which the catalyst has been removed to some extent.

[0008] However, in the above patent, when a poor solvent is added to a good solvent for recrystallization, sticky catalyst material still remains at the interface, and even after recrystallization, the catalyst still exists in the monomer at 90 ppm or more. This damages the anion reaction sites during anion polymerization of the recrystallized monomer, resulting in a problem that the degree of polymerization cannot be increased or the conversion rate is low. Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to provide a novel method for purifying laurolactam, which comprises producing laurolactam from cyclododecanone oxime via the Beckmann potential reaction, and recrystallizing the synthesized laurolactam without sticky substances during the treatment with a good solvent and a poor solvent, thereby maintaining the residual amount of catalyst at 20 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less.

[0010] Also provided is the synthesis value of laurolactam for said purification method.

[0011] Another object of the present invention is to provide laurolactam synthesized by the above method for producing laurolactam, in which the catalyst component content is maintained at 10 ppm or less.

[0012] Also provided is a method for producing polylaurolactam at a high conversion rate by anionic polymerization of the synthesized laurolactam. [Means for solving the problem]

[0013] One embodiment provides a method for producing laurolactam, comprising: a) synthesizing laurolactam from cyclododecanone oxime via a Beckmann rearrangement in the presence of a TCT catalyst without using a co-catalyst; b) mixing the laurolactam synthesized in step a) with a good solvent to remove the catalyst; and c) mixing the laurolactam from which the catalyst has been removed in step b) with a poor solvent to recrystallize it.

[0014] The Beckmann potential reaction in step a) can synthesize cyclododecanone oxime to laurolactam using only cyanuric chloride (TCT) in a solvent containing isopropylcyclohexane (IPCH), without using a catalyst that does not contain zinc chloride (ZnCl), the co-catalyst used in Korean Patent Application No. 2019-161823 filed by the applicant and not published as of the filing date of this application.

[0015] The step a) may further include distilling the synthesized laurolactam to remove the solvent.

[0016] In the step b), the catalyst can be removed by utilizing the difference in solubility between the catalyst and a good solvent for laurolactam.

[0017] The good solvent may be a C1 to C4 hydrocarbon organic solvent containing one or more functional groups selected from the group consisting of a hydroxyl group, an amine group, and a thiol group.

[0018] In the step c), laurolactam can be recrystallized by utilizing the difference in solubility of laurolactam in a good solvent and a poor solvent.

[0019] The good solvent and the poor solvent may be miscible.

[0020] The anti-solvent can be distilled water or deionized water.

[0021] The good solvent and poor solvent may be added in a weight ratio of 1:1.5 to 1:3.

[0022] The method may further comprise evaporating the recrystallized laurolactam to remove polymeric substances (Heavies) as a liquid phase and / or a solid phase, and isolating laurolactam as a gas phase.

[0023] Another embodiment provides a method for synthesizing laurolactam, including: a first reactor for synthesizing laurolactam from cyclododecanone oxime by a Beckmann potential reaction in the presence of a TCT catalyst; an evaporator for removing the solvent from the laurolactam synthesized in the first reactor; a second reactor for mixing the laurolactam from which the solvent has been removed in the evaporator with a good solvent and removing the catalyst; and a third reactor for mixing the laurolactam from which the catalyst has been removed in the second reactor with an empty solvent for recrystallization.

[0024] The second reactor may further include a filter for removing catalyst deposited therein.

[0025] The method may further include a film evaporator to separate Heavies from the recrystallized laurolactam.

[0026] Another embodiment provides a laurolactam composition synthesized by the method for producing laurolactam.

[0027] The laurolactam composition may contain 5% by weight or less of the catalyst used in the Beckmann potential reaction based on the total weight of the laurolactam composition.

[0028] Another embodiment provides a method for producing polylaurolactam, which comprises anionically polymerizing the laurolactam composition in the presence of an anionic initiator to produce polylaurolactam.

[0029] The anionic initiator may include one or more selected from the group consisting of NaH, n-BuLi, KH, and LiH.

[0030] The anionic polymerization can proceed at 250 to 350° C. for 10 to 60 minutes.

[0031] The polymerized polylaurolactam may have a weight average molecular weight of greater than 6,000. [Effects of the Invention]

[0032] After synthesizing laurolactam by the Beckmann potential reaction, the catalyst and solvent remaining in the reaction product can be effectively removed by a simplified process.

[0033] The purified laurolactam monomer can be utilized to carry out anionic polymerization reactions with high conversion rates. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will be described in detail below. Terms used in this specification should be interpreted as generally understood by a person of ordinary skill in the art unless otherwise defined. The drawings and examples in this specification are intended to enable a person of ordinary skill in the art to easily understand and practice the present invention. Contents that are detrimental to the gist of the present invention may be omitted from the drawings and examples, and the present invention is not limited to the drawings and examples.

[0035] As used herein, the singular forms of terms can be construed to include the plural forms as well, unless otherwise specified.

[0036] In the context of this invention, catalyst refers to a catalyst system that uses only TCT catalyst and does not contain any co-catalyst.

[0037] Hereinafter, a method for producing laurolactam according to one embodiment will be described.

[0038] The method for producing laurolactam includes the steps of: a) synthesizing laurolactam from cyclododecanone oxime by Beckmann potential reaction in the presence of a TCT catalyst; b) mixing the laurolactam synthesized in step a) with a good solvent and removing the catalyst; and c) mixing the laurolactam from which the catalyst has been removed in step b) with an empty solvent and recrystallizing it.

[0039] Step a) is a step of synthesizing cyclododecanone oxime to laurolactam using a Beckmann potential reaction in the presence of a TCT catalyst, and the Beckmann potential reaction can synthesize cyclododecanone oxime to laurolactam via a cyanuric chloride (TCT) catalyst in a solvent.

[0040] Specifically, the Beckmann potential reaction in step a) can proceed at a temperature of 70 to 130°C, preferably 90 to 110°C, and more preferably 95 to 100°C. The reaction time can be 1 to 20 minutes, preferably 5 to 20 minutes, and more preferably 5 to 15 minutes. If the reaction temperature is too high, a large amount of by-products such as polymeric substances (Heavies) is produced. If the reaction temperature is too low, the reaction rate is not fast enough, making it difficult to apply to commercial processes. Furthermore, if the reaction time is less than 1 minute, cyclododecanone oxime cannot be sufficiently rearranged to laurolactam, and if it exceeds 20 minutes, excessive side reactions occur, which is undesirable.

[0041] Meanwhile, the Beckmann potential reaction refers to a potential reaction in which a ketoxime is converted to an acid amide, and particularly in the present invention, it can refer to a reaction in which the cyclododecanone oxime is converted to laurolactam.

[0042] The catalyst is cyanuric chloride (TCT). Specifically, the catalyst may be contained in an amount of 0.1 to 10 parts by weight, preferably 0.1 to 5 parts by weight, and more preferably 0.5 to 2 parts by weight, per 100 parts by weight of cyclododecanone oxime. If the catalyst content is too low, the Beckmann potential reaction cannot proceed sufficiently. If the catalyst content is too high, a high content of catalytic material remains in the reaction product after completion of the reaction, making it difficult to effectively remove it during the purification step.

[0043] More specifically, the catalyst may contain cyanuric chloride and zinc chloride in a weight ratio of 2:1 to 1:1, preferably 1.5:1 to 1:1, and more preferably 1.3:1 to 1:1, thereby effectively synthesizing laurolactam by suppressing the decrease in conversion rate due to the water content, which is a limiting factor in the Beckmann potential reaction, and after the reaction is completed, the catalyst remaining in the reaction product can be easily removed by a simplified process.

[0044] The solvent is preferably an organic solvent containing, for example, isopropylcyclohexane (IPCH). Due to its strong non-polarity, this solvent can be used to successfully convert cyclododecanone oxime to laurolactam using the Beckmann potential reaction. Furthermore, due to its large difference in boiling point from the reaction product, the solvent can be easily removed by distilling the reaction product. Therefore, high-purity laurolactam can be effectively produced.

[0045] The organic solvent containing IPCH can be used in an amount of 30 to 50 parts by weight per 100 parts by weight of cyclododecanone oxime. When the amount is within this range, the Beckmann potential reaction of cyclododecanone oxime is facilitated, and the solvent can be easily removed by distilling the reaction product. Therefore, high-purity laurolactam can be effectively produced.

[0046] Subsequently, in step b), the laurolactam synthesized in step a) is mixed with a good solvent, and the catalyst is removed. The good solvent can be a C1-C4 hydrocarbon organic solvent, preferably a C1-C4 hydrocarbon organic solvent containing one or more functional groups selected from the group consisting of a hydroxy group, an amine group, and a thiol group, more preferably a C1-C4 hydrocarbon containing a hydroxy group, or a C1-C4 alcohol.

[0047] When the good solvent is added, the catalyst can be removed by taking advantage of the difference in solubility between the catalyst and laurolactam. Specifically, the catalyst does not dissolve in the good solvent and precipitates as solid particles, whereas laurolactam has high solubility in the good solvent and may be substantially completely dissolved in the good solvent and not precipitate. The catalyst precipitated as particles can then be easily removed using a filter. If too little good solvent is added, some of the laurolactam may not dissolve and remain as a solid, being removed through the filter along with the remaining catalyst, reducing the yield of laurolactam. Furthermore, some of the laurolactam not dissolved in the good solvent may aggregate with the remaining catalyst and pass through the filter, remaining. Conversely, if too much good solvent is added, recrystallization of laurolactam in the subsequent step c) may be difficult. Therefore, the laurolactam synthesized in step a) and the good solvent can be mixed in a weight ratio of 1:4 to 1:7, preferably 1:5 to 1:7, and more preferably 1:6 to 1:7.

[0048] Meanwhile, in the specification of the present invention, a good solvent means a solvent that has a high affinity for laurolactam and can dissolve it well, and a poor solvent means a solvent that has a low affinity for laurolactam and cannot dissolve it well.

[0049] In step c), the laurolactam from which the catalyst has been removed in step b) is mixed with a poor solvent to recrystallize it. The poor solvent can be a substance miscible with the good solvent, specifically distilled water or deionized water. When the poor solvent is added, the laurolactam can be recrystallized by utilizing the difference in solubility between the good solvent and the poor solvent. Specifically, laurolactam has high solubility in a good solvent and low solubility in a poor solvent. When the poor solvent is added to the good solvent in step b), the solubility of laurolactam decreases as the concentration of the good solvent decreases, resulting in the recrystallization of laurolactam and precipitation as a solid.

[0050] The good solvent and poor solvent can be added in a weight ratio of, for example, 1:1.5 to 1:3, preferably 1:2 to 1:3, and more preferably 1:2 to 1:2.5. Adding an excess amount of the good solvent relative to the poor solvent is undesirable because a portion of the laurolactam may not precipitate as a solid but may remain dissolved in the good solvent, potentially resulting in a low yield of purified laurolactam.

[0051] Subsequently, the recrystallized laurolactam can be evaporated to remove polymeric substances (Heavies) in the liquid and / or solid phases, and the laurolactam can be separated in the gas phase, which is preferable because it can result in the purification of highly pure laurolactam.

[0052] The evaporation can be carried out, for example, in a film evaporator, although the invention is not limited thereto.

[0053] Meanwhile, a film evaporator is an evaporation device used to obtain a desired substance with high purity from a mixed substance (liquid) through a distillation reaction. That is, it forms a thin film from the liquid mixture using physical force, maximizing the surface area of ​​the mixture and increasing the evaporation rate, allowing for separation of substances with high purity.

[0054] The present invention also provides an apparatus for synthesizing laurolactam according to the method for producing laurolactam. In this case, since the technical concept is substantially the same as that described in the method for producing laurolactam, it goes without saying that the materials used, reaction conditions, etc. are interpreted as being substantially the same as those described above.

[0055] Another embodiment of the apparatus for synthesizing laurolactam will now be described.

[0056] The laurolactam synthesis apparatus according to the present invention comprises a first reactor for synthesizing laurolactam from cyclododecanone oxime by a Beckmann potential reaction in the presence of a catalyst, an evaporator for removing the solvent from the laurolactam synthesized in the first reactor, a second reactor for mixing the laurolactam from which the solvent has been removed in the evaporator with a good solvent and removing the catalyst, and a third reactor for mixing the laurolactam from which the catalyst has been removed in the second reactor with an empty solvent for recrystallization.

[0057] The laurolactam synthesis apparatus may further include a filter for removing solid catalyst precipitated in the second reactor.

[0058] The laurolactam synthesis apparatus may further include a film evaporator for separating polymeric substances (Heavies) from the recrystallized laurolactam.

[0059] The "reactor," "(film) evaporator," and "filter" of the present invention may be any of various known reactors, (film) evaporators, and filters, and their specifications and sizes are not limited and can be appropriately adjusted depending on the scale and environment of the process. Furthermore, various inlet and outlet pipes for allowing materials to flow in and out of each reactor, (film) evaporator, and filter are provided, and the use of various devices for adjusting the inflow and outflow rates and controlling these devices is within the skill of a person skilled in the art.

[0060] Hereinafter, a laurolactam composition synthesized by the method for producing laurolactam according to another embodiment will be provided.

[0061] The laurolactam composition may have a conversion rate of cyclododecanone oxime of 98 to 99%, preferably 99 to 99.5%, and more preferably 99.5 to 99.9%, and a selectivity for laurolactam of 97 to 98%, preferably 98 to 99%, and more preferably 99 to 99.5%.

[0062] In addition, the laurolactam composition may contain a catalyst used in the Beckmann potential reaction in an amount of 5% by weight or less, preferably less than 5% by weight, more preferably 3% by weight or less, and most preferably 1% by weight or less or 0.5% by weight or less, based on the total weight of the laurolactam composition. If the catalyst content exceeds this range, the activity of the anionic initiator used in the anionic polymerization is significantly reduced, making it difficult for the polymerization reaction to proceed.

[0063] Meanwhile, the content of the catalyst contained in the laurolactam composition can be measured using an ICP (Inductively Coupled Plasma Spectrometer) analyzer.

[0064] Hereinafter, another embodiment provides a method for producing polylaurolactam, which may include anionically polymerizing the laurolactam composition in the presence of an anionic initiator.

[0065] Polymerization of purified laurolactam and any novel monomer (comonomer) can be carried out for 10 to 60 minutes at 200 to 350° C. Specifically, the polymerization reaction can be carried out at 200 to 300° C., preferably 220 to 250° C., for 10 to 60 minutes, preferably 10 to 50 minutes, and more preferably 20 to 40 minutes.

[0066] The polymerized polylaurolactam can be a laurolactam-containing polymer, such as a copolyamide or a polyether-block amide, preferably polyamide 12 (nylon 12).

[0067] The anionic initiator may specifically include one or more selected from the group consisting of NaH, LiH, KH, and n-BuLi. It is known that the catalytic material used in the Beckmann potential reaction according to one embodiment of the present invention significantly reduces the activity of the anionic initiator. However, the method for producing laurolactam according to one embodiment of the present invention and the laurolactam composition produced thereby can effectively remove the catalytic material, thereby enabling anionic polymerization of laurolactam monomer with a high degree of polymerization in the presence of the anionic initiator.

[0068] The anionic polymerization can be carried out in a batch reactor or a continuous reactor (CSTR, PFR, or PBR), preferably in a continuous reactor, although the present invention is not limited thereto.

[0069] The weight average molecular weight of the polymerized polylaurolactam is more than 6,000, and can be preferably 6,500 to 14,000, and more preferably 8,000 to 12,000 or 9,000 to 11,000.

[0070] The present invention will be described in detail below with reference to examples. However, these examples are for the purpose of explaining the present invention in more detail, and the scope of the present invention is not limited to the following examples.

[0071] Example 1 A 100ml round flask was charged with 3g of cyclododecanone oxime, 12g of isopropylcyclohexane, and 0.045g of cyanuric chloride. The temperature was adjusted to 95°C using a heating mantle, and the reaction was carried out with stirring at 200 rpm or higher. The reaction was completed in 5 minutes, with a conversion rate of cyclododecanone oxime of over 99% and a selectivity to laurolactam of over 99%.

[0072] 100 g of the product was poured into an evaporator and distilled at 150°C, with IPCH being removed from the top of the evaporator. The resulting brown solid (laurolactam before purification) was dissolved in 700 g of ethanol in a flask. The floating solid (catalyst) was removed using a 0.22 μm filter, and 1,600 g of water was poured into the ethanol-dissolved laurolactam (LL) to recrystallize the laurolactam solid. The recrystallized laurolactam was separated using a filter, and the Heavies were removed from the bottom using a film evaporator, and laurolactam was separated from the top. The residual catalyst content and laurolactam yield were measured and are listed in Table 1 below. During the crystallization, there was no adhesion or separation between the interfaces.

[0073] Thereafter, 50 g of the produced laurolactam and a catalyst were added to a 100 ml round flask in a weight ratio of laurolactam:NaH:EBS (ethylene bis stearamide):TEOS (tetraethyl orthosilicate):CO2 = 100:0.6:0.36:0.15:0.15, and an anionic polymerization reaction was carried out at 240°C for 30 minutes to produce polyamide 12. The degree of polymerization of polyamide 12 is shown in Table 1 below.

[0074] Example 2 Laurolactam was separated in the same manner as in Example 1 except that 300 g of ethanol was added, and the residual catalyst content and laurolactam yield were measured, and the results are shown in Table 1 below.

[0075] Subsequently, an anionic polymerization reaction was carried out in the same manner as in Example 1 to produce polyamide 12, and the polymerization degree of polyamide 12 is shown in Table 1 below.

[0076] Example 3 Laurolactam was separated in the same manner as in Example 1, except that 700 g of water was added to the laurolactam dissolved in ethanol, and the residual catalyst content and LL yield were measured, and the results are shown in Table 1 below.

[0077] Subsequently, an anionic polymerization reaction was carried out in the same manner as in Example 1 to produce polyamide 12. The polymerization degree of polyamide 12 is shown in Table 1 below.

[0078] Comparative Example 1 100 g of the product of Preparation Example 1 was poured into an evaporator and distilled at 150°C to remove IPCH at the top of the evaporator. The brown solid produced was separated into Heavies at the bottom using a film evaporator, and laurolactam was separated from the top. The residual catalyst content and laurolactam yield are shown in Table 1 below.

[0079] Subsequently, an anionic polymerization reaction was carried out in the same manner as in Example 1 to produce polyamide 12. The polymerization degree of polyamide 12 is shown in Table 1 below.

[0080] Comparative Example 2 Laurolactam was separated in the same manner as in Example 1, except that water was not added to the laurolactam dissolved in ethanol, and the residual catalyst content and laurolactam yield are shown in Table 1 below.

[0081] Subsequently, an anionic polymerization reaction was carried out in the same manner as in Example 1 to produce polyamide 12. The polymerization degree of polyamide 12 is shown in Table 1 below.

[0082] Comparative Example 3 The same procedure was carried out as in Example 1, except that 0.045 g of cyanuric chloride and 0.03 g of zinc chloride were added as catalysts for the reaction. The results are shown in Table 1.

[0083] Subsequently, an anionic polymerization reaction was carried out in the same manner as in Example 1 to produce polyamide 12, and the polymerization degree of polyamide 12 is shown in Table 1 below.

[0084] *Residual catalyst content measurement method Laurolactam is a solid at room temperature and therefore indistinguishable from the solid catalyst used in its synthesis, but when melted at 150°C, the catalyst remains as a black solid, making it possible to confirm whether or not a solid catalyst remains. The catalyst remaining in the laurolactam produced in Preparation Example 1 can be separated as a solid at high temperature and weighed, or its content can be measured using a solvent that can dissolve laurolactam.

[0085] *Laurolactam yield measurement method 100 g of the product of Preparation Example 1 was measured by GC to calculate the laurolactam content (L1), and the laurolactam content (L2) obtained from the top of the film evaporator of Example 1 was measured to calculate the laurolactam yield (L / L 21 *100, % was calculated.

[0086] *Method for measuring the molecular weight (degree of polymerization) of PA12 After the anionic polymerization reaction was completed, the agitator torque value was calculated from the polymerization reactor, and the weight average molecular weight of PA12 was calculated by back-calculating the calculated torque value.

[0087] *Residual catalyst analysis method The content of Cl anions, a residual catalyst component, was analyzed using Combustion IC (Combustion Ion Chromatography). Chlorine compounds were burned with Ar / O2 gas and the ions generated by absorption into the H2O2 solution were separated using an ion exchange column in the ion chromatograph, and then quantitatively analyzed using a suppressor detector.

[0088] [Table 1]

[0089] Referring to Table 1, in Examples 1 to 3, the residual catalyst was substantially removed, and anionic polymerization was carried out using purified laurolactam, resulting in the production of PA12. However, in Comparative Example 3, in which a cocatalyst was used as a catalyst component in Example 1, a large amount of catalyst component (94 ppm) still remained, and the molecular weight after anionic polymerization was also lower than that of the present invention.

[0090] As described above, the present invention has been described using specific details and limited examples, but these are provided to facilitate a more comprehensive understanding of the present invention, and the present invention is not limited to the above examples, and those skilled in the art will appreciate that various modifications and variations can be made from these descriptions. Therefore, the spirit of the present invention should not be limited to the described examples, and all aspects equivalent to or equivalent to the scope of the claims, as well as the following claims, are considered to fall within the spirit of the present invention.

Claims

1. a) synthesizing cyclododecanone oxime to laurolactam by Beckmann rearrangement in the presence of cyanuric chloride (TCT) as a catalyst in a solvent containing isopropylcyclohexane (IPCH); a-1) distilling the synthesized laurolactam to remove the solvent; b) mixing the laurolactam from which the solvent has been removed in step a-1) with a good solvent, and removing the catalyst; c) mixing the laurolactam from which the catalyst has been removed in step b) with a poor solvent to recrystallize it; Including, The catalyst is a mixture of cyanuric chloride (TCT) and zinc chloride (ZnCl ２ ) rather than a mixed catalyst, the good solvent has a higher solubility for laurolactam than the poor solvent, the good solvent is ethanol, and the poor solvent is distilled water or deionized water; the laurolactam from which the solvent has been removed in step a-1) and the good solvent are mixed in a weight ratio of 1:3 to 1:7, and the good solvent and the poor solvent are injected in a weight ratio of 1:1 to 1:5.3; Method for producing laurolactam.

2. 2. The method for producing laurolactam according to claim 1, wherein step b) comprises removing the catalyst by utilizing a difference in solubility between the catalyst and a good solvent for laurolactam.

3. 2. The method for producing laurolactam according to claim 1, wherein step c) comprises recrystallizing laurolactam by utilizing the difference in solubility of laurolactam in a good solvent and a poor solvent.

4. The method for producing laurolactam according to claim 1, wherein the good solvent and the poor solvent are miscible with each other.

5. 2. The method for producing laurolactam according to claim 1, further comprising the step of evaporating the recrystallized laurolactam to remove polymeric substances (heavies) in the liquid phase and / or solid phase, and isolating laurolactam in the gas phase.

6. a first reactor for synthesizing laurolactam from cyclododecanone oxime by Beckmann rearrangement in the presence of a cyanuric chloride (TCT) catalyst and a solvent containing isopropylcyclohexane (IPCH); an evaporator for removing the solvent from the laurolactam synthesized in the first reactor; and a second reactor for mixing the laurolactam from which the solvent has been removed in the evaporator with a good solvent and removing the catalyst; a third reactor in which the laurolactam from which the catalyst has been removed in the second reactor is mixed with a poor solvent to be recrystallized; Including, The catalyst is a mixture of cyanuric chloride (TCT) and zinc chloride (ZnCl ２ ) rather than a mixed catalyst, the good solvent has a higher solubility for laurolactam than the poor solvent, the good solvent is ethanol, and the poor solvent is distilled water or deionized water; the laurolactam from which the solvent has been removed by the evaporator and the good solvent are mixed in a weight ratio of 1:3 to 1:7; and the good solvent and the poor solvent are injected in a weight ratio of 1:1 to 1:5.

3. Laurolactam synthesis unit.

7. 7. The apparatus for synthesizing laurolactam according to claim 6, further comprising a filter for removing catalyst precipitated in the second reactor.

8. 7. The laurolactam synthesis apparatus according to claim 6, further comprising a film evaporator for separating heavy substances (heavies) from the recrystallized laurolactam.

9. (S1) synthesizing laurolactam from cyclododecanone oxime by Beckmann rearrangement in the presence of cyanuric chloride (TCT) as a catalyst and in a solvent containing isopropylcyclohexane (IPCH); (S2) distilling the synthesized laurolactam to remove the solvent; (S3) mixing the laurolactam from which the solvent has been removed in the step (S2) with a good solvent to remove the catalyst; (S4) mixing the laurolactam from which the catalyst has been removed in the step (S3) with a poor solvent to recrystallize it; (S5) anionically polymerizing the recrystallized laurolactam in the presence of an anionic initiator to prepare polylaurolactam; Including, The catalyst is a mixture of cyanuric chloride (TCT) and zinc chloride (ZnCl ２ ) rather than a mixed catalyst, the good solvent has a higher solubility for laurolactam than the poor solvent, the good solvent is ethanol, and the poor solvent is distilled water or deionized water; the laurolactam from which the solvent has been removed in step (S2) and the good solvent are mixed in a weight ratio of 1:3 to 1:7; and the good solvent and the poor solvent are injected in a weight ratio of 1:1 to 1:5.

3. Method for producing polylaurolactam.

10. The method for producing polylaurolactam according to claim 9, wherein the anionic initiator comprises one or more selected from the group consisting of NaH, n-BuLi, KH, and LiH.

11. 10. The method for producing polylaurolactam according to claim 9, wherein the anionic polymerization is carried out at 200 to 350° C. for 10 to 60 minutes.

12. The method for producing polylaurolactam according to claim 9, wherein the weight average molecular weight of the polymerized polylaurolactam exceeds 6,000.

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