Preparation method of laurolactam and synthesis device thereof, and preparation method of polylaurolactam

Abstract

The present invention relates to a method for preparing laurolactam and a synthesis device thereof, a laurolactam composition prepared by the synthesis device and a method for preparing polylaurolactam using the laurolactam composition. The method for preparing laurolactam comprises: step a), synthesizing cyclododecanone oxime into laurolactam by Beckmann rearrangement reaction under a catalyst system; step b), mixing the laurolactam synthesized in the step a) into a good solvent and removing the catalyst system; and step c), mixing the laurolactam from which the catalyst system is removed in the step b) into a poor solvent for recrystallization.

Description

Technical Field

[0001] The invention relates to a method for preparing laurolactam and a synthesis device thereof, a laurolactam composition prepared by the method, and a method for preparing polylaurolactam using the laurolactam composition. Background Art

[0002] Typically, the method for preparing industrial amine compounds utilizes the Beckmann rearrangement reaction to convert the corresponding oxime compound. For example, cyclododecanone oxime can be synthesized into lauryl lactam by the Beckmann rearrangement reaction. However, the process of the Beckmann rearrangement reaction is a rather complicated process, and concentrated sulfuric acid and oleum will be used as catalysts, which are strong acids and require high contents, so a large amount of ammonium sulfate by-products will be produced during neutralization, and there is a limitation that equipment for treatment is required. In addition, since the Beckmann rearrangement reaction will be carried out on a solvent, the above-mentioned solvent needs to have a high solubility of cyclododecanone oxime and should not react with the concentrated sulfuric acid and oleum as the above-mentioned catalysts, so the selection is limited.

[0003] On the other hand, the macromolecular substances of aliphatic carbonate macromolecules, polylaurolactam, etc. can be synthesized by anion polymerization of laurolactam monomers, etc., but the purity of the above-mentioned laurolactam monomers will have a great influence on the activity of the polymerization reaction. In the past, the reaction product containing laurolactam was prepared by Beckmann rearrangement reaction and the macromolecular substance (Heavies) was removed with solid phase and / or liquid phase after the solvent used was distilled to purify laurolactam, but there was a problem that the activity of the anion polymerization reaction dropped sharply due to the residual trace catalyst in the final laurolactam product. Therefore, it is necessary to purify the high-purity laurolactam and improve the anion polymerization activity of the laurolactam monomers, etc. by removing the catalyst remaining after the Beckmann rearrangement reaction through a simple process. Summary of the invention

[0004] Technical issues

[0005] The object of the present invention is to provide a method for preparing laurolactam, that is, preparing cyclododecanone oxime into laurolactam through Beckmann rearrangement reaction, purifying the synthesized laurolactam through a simple process, thereby removing residual catalyst and preparing high-purity laurolactam.

[0006] Furthermore, the present invention provides a synthesis device for the laurolactam.

[0007] Furthermore, the present invention provides a laurolactam composition synthesized by the laurolactam preparation method.

[0008] Furthermore, the present invention provides a method for preparing polylaurolactam at a high conversion rate by utilizing anionic polymerization reaction on synthesized laurolactam.

[0009] Technical Solution

[0010] According to one embodiment, the present invention provides a method for preparing laurolactam, comprising: step a), synthesizing cyclododecanone oxime into laurolactam by Beckmann rearrangement reaction in the presence of a catalyst system; step b), mixing the laurolactam synthesized in the above step a) with a good solvent and removing the above catalyst system; and step c), mixing the laurolactam from which the above catalyst system is removed in the above step b) with a poor solvent for recrystallization.

[0011] In the Beckmann rearrangement reaction of step a), cyclododecanone oxime may be synthesized into laurolactam by a catalyst system comprising cyanuric chloride (TCT) and zinc chloride (ZnCl 2 ) in a solvent comprising isopropylcyclohexane (IPCH).

[0012] The step a) may further include the following step: removing the solvent by distilling the synthesized laurolactam.

[0013] In the above step b), the catalyst system may be removed by utilizing the difference in solubility between the above catalyst system and the good solvent for laurolactam.

[0014] 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.

[0015] In the step c), the laurolactam may be recrystallized by utilizing the difference between the solubility of the laurolactam in a good solvent and the solubility of the laurolactam in a poor solvent.

[0016] The good solvent and the poor solvent may be miscible.

[0017] The poor solvent may be distilled water or deionized water.

[0018] The good solvent and the poor solvent may be injected at a weight ratio of 1:1.5 to 1:3.

[0019] The present invention may further include the following step: removing high molecular weight substances (Heavies) in a liquid phase and / or a solid phase by evaporating the recrystallized laurolactam, and separating the laurolactam in a gas phase.

[0020] According to another example, the present invention provides a laurolactam synthesis device, which includes: a first reactor, in the presence of a catalyst system, cyclododecanone oxime is synthesized into laurolactam by Beckmann rearrangement reaction; an evaporator, removing the solvent of the laurolactam synthesized in the above-mentioned first reactor; a second reactor, mixing the laurolactam from which the solvent is removed in the above-mentioned evaporator with a good solvent and removing the above-mentioned catalyst system; and a third reactor, mixing the laurolactam from which the catalyst system is removed in the above-mentioned second reactor with a poor solvent for recrystallization.

[0021] The present invention may further include a filter for removing the catalyst system precipitated in the second reactor.

[0022] The present invention may further include a film evaporator for separating high molecular weight substances (Heavies) from the recrystallized laurolactam.

[0023] According to another embodiment, the present invention provides a laurolactam composition synthesized by the above-mentioned preparation method of laurolactam.

[0024] According to the present invention, the laurolactam composition comprises less than 5 weight percent of the catalyst system for Beckmann rearrangement reaction relative to the total weight of the laurolactam composition.

[0025] According to another example, the present invention provides a method for preparing polylaurolactam, wherein the polylaurolactam is prepared by anion polymerization of the laurolactam composition in the presence of a negative ion initiator.

[0026] The anion initiator may include one or more selected from the group consisting of NaH, n-BuLi, KH, and LiH.

[0027] The anionic polymerization may be performed at a temperature of 250° C. to 350° C. for 10 minutes to 60 minutes.

[0028] The weight average molecular weight of the polymerized polylaurolactam may be greater than 6,000.

[0029] Effects of the Invention

[0030] After the synthesis of laurolactam by the Beckmann rearrangement reaction, the catalyst system and the solvent remaining in the reaction product can be effectively removed by only a simple step.

[0031] Purified laurolactam monomers can be used to perform anionic polymerization reactions with high conversion rates. DETAILED DESCRIPTION

[0032] The present invention is described in detail below. Unless otherwise defined, the terms used in this specification should be interpreted as commonly understood by those skilled in the art. The drawings and embodiments in this specification are intended to make it easy for those skilled in the art to understand and implement the present invention. Contents that may obscure the subject matter of the invention may be omitted in the drawings and embodiments, and the present invention is not limited to the drawings and embodiments.

[0033] Unless otherwise specified, the singular form of the terms used in the present invention may be construed as also including the plural form.

[0034] In the present specification, the catalyst system means a composite catalyst system (Catalyst system) including two or more compounds, for example, it may refer to a catalyst system including a main catalyst and a sub-catalyst.

[0035] Hereinafter, a method for preparing laurolactam according to an example will be described.

[0036] The preparation method of laurolactam comprises: step a), synthesizing cyclododecanone oxime into laurolactam by Beckmann rearrangement reaction in the presence of a catalyst system; step b), mixing the laurolactam synthesized in the step a) with a good solvent and removing the catalyst system; and step c), mixing the laurolactam from which the catalyst system is removed in the step b) with a poor solvent for recrystallization.

[0037] The above step a) is a step of synthesizing cyclododecanone oxime into laurolactam by Beckmann rearrangement reaction under a catalyst system. In the above Beckmann rearrangement reaction, cyclododecanone oxime is synthesized into laurolactam by a catalyst containing cyanuric chloride (TCT) and zinc chloride (ZnCl2) in a solvent.

[0038] Specifically, in the above step a), the Beckmann rearrangement reaction is carried out at a temperature of 70°C to 130°C, preferably 90°C to 110°C, and more preferably 95°C to 100°C for 1 minute to 20 minutes, preferably 5 minutes to 20 minutes, and more preferably 5 minutes to 15 minutes. If the reaction temperature in the above reaction is too high, a lot of by-products such as high molecular weight substances (Heavies) will be produced. If the reaction temperature is too low, the reaction speed is not fast enough, so it is difficult to use in commercial processes. In addition, if the reaction time is less than 1 minute, cyclododecanone oxime may not be fully rearranged to lauryl lactam. If the reaction time is greater than 20 minutes, excessive side reactions will be produced, which is not preferred.

[0039] On the other hand, the Beckmann rearrangement reaction means a rearrangement reaction of converting a ketone oxime into an acid amine, and particularly, in the present invention, may refer to a reaction of rearranging the above-mentioned cyclododecanone oxime into laurolactam.

[0040] The catalyst system may include cyanuric chloride (TCT) and zinc chloride (ZnCl2), and cyanuric chloride or the like may be used as a main catalyst, and zinc chloride or the like may be used as a secondary catalyst, and may be used together with the main catalyst. Specifically, relative to 100 parts by weight of cyclododecanone oxime, 0.1 to 10 parts by weight of the main catalyst and secondary catalyst may be included, preferably 0.1 to 5 parts by weight, and more preferably 0.5 to 2 parts by weight. If the content of the catalyst system is too low, the Beckmann rearrangement reaction cannot be fully carried out. If the content of the catalyst system is too high, a high content of the catalyst system substance will remain in the reaction product after the reaction is completed, and it is difficult to effectively remove it in the purification step.

[0041] More specifically, in the above catalyst system, cyanuric chloride and zinc chloride may be included in a weight ratio of 2:1 to 1:1, preferably in a weight ratio of 1.5:1 to 1:1, and more preferably in a weight ratio of 1.3:1 to 1:1. In this way, laurolactam can be efficiently synthesized by suppressing the phenomenon of reduced conversion rate due to limited water content in the Beckmann rearrangement reaction, and the catalyst system remaining in the reaction product can be easily removed through a simple process after the reaction is completed.

[0042] In terms of the above-mentioned solvent, an organic solvent containing isopropylcyclohexane (IPCH) is preferred. The above-mentioned solvent can be used to successfully prepare cyclododecanone oxime into laurolactam by Beckmann rearrangement reaction by virtue of its strong non-polarity. There is a large boiling point difference between the above-mentioned solvent and the reaction product, so the solvent can be easily removed by distilling the reaction product. Therefore, high-purity laurolactam can be effectively prepared.

[0043] The organic solvent containing isopropylcyclohexane (IPCH) can be used in an amount of 30 to 50 parts by weight relative to 100 parts by weight of cyclododecanone oxime. If the content is within the above content range, the Beckmann rearrangement reaction of cyclododecanone oxime can be easily performed, and the solvent can be easily removed by distilling the reaction product. Therefore, high-purity laurolactam can be effectively prepared.

[0044] Next, the step b) is a step of mixing the laurolactam synthesized in the step a) with a good solvent and removing the catalyst system. The good solvent may be a C1 to C4 hydrocarbon organic solvent, preferably a C1 to C4 hydrocarbon organic solvent containing one or more functional groups selected from the group consisting of hydroxyl, amine and thiol groups, more preferably a C1 to C4 hydrocarbon containing a hydroxyl group or a C1 to C4 ethanol.

[0045] In the case of mixing the above-mentioned good solvent, the solubility difference of the good solvent for the above-mentioned catalyst system and laurolactam can be used to remove the catalyst system. Specifically, the above-mentioned catalyst system is insoluble in the good solvent, but is precipitated in the form of solid particles, while the solubility of laurolactam in the good solvent is very high, so it can actually be completely dissolved in the good solvent without being precipitated. Afterwards, the catalyst system precipitated in the form of particles can be easily removed by a filter. In this case, if the injection amount of the good solvent is too small, part of the laurolactam will not be dissolved, but will exist in a solid form and be removed by the filter together with the residual catalyst, which will cause the yield of laurolactam to decrease, and part of the laurolactam that is not dissolved in the good solvent may agglomerate with the catalyst system and remain after passing through the filter. On the contrary, if an excessive amount of good solvent is injected, it may be difficult to achieve recrystallization of laurolactam in the subsequent step c). Therefore, the laurolactam synthesized in step a) and the above-mentioned good solvent can be mixed in a weight ratio of 1:4 to 1:7, preferably a weight ratio of 1:5 to 1:7, and more preferably a weight ratio of 1:6 to 1:7.

[0046] On the other hand, a good solvent in the specification of the present invention may mean a solvent that can well dissolve laurolactam due to its high affinity for laurolactam, and a poor solvent may mean a solvent that cannot well dissolve laurolactam due to its low affinity for laurolactam.

[0047] Next, the above step c) is a step of mixing the laurolactam from which the above catalyst system is removed in the above step b) into a poor solvent for recrystallization. The above poor solvent can be a substance miscible with the above good solvent, specifically distilled water or deionized water. When the above poor solvent is mixed, the laurolactam is recrystallized by utilizing the difference between the solubility of the above laurolactam in the good solvent and the solubility in the poor solvent. Specifically, the above laurolactam has the characteristics of high solubility in the good solvent and low solubility in the poor solvent. When the above poor solvent is mixed into the good solvent that dissolves the laurolactam in the above step b), as the concentration of the good solvent decreases, the solubility of the laurolactam will decrease, and finally, the laurolactam can be recrystallized and precipitated in a solid form.

[0048] The good solvent and the poor solvent may be injected at a weight ratio of 1:1.5 to 1:3, preferably at a weight ratio of 1:2 to 1:3, and more preferably at a weight ratio of 1:2 to 1:2.5. If too much good solvent is injected relative to the poor solvent, part of the laurolactam may not be precipitated in a solid form, but may exist in a state dissolved in the good solvent, which may reduce the yield of the purified laurolactam, and is therefore not preferred.

[0049] Next, the following step may be performed, that is, the recrystallized laurolactam may be evaporated to remove high molecular weight substances (Heavies) in the liquid phase and / or solid phase, and the laurolactam may be separated in the gas phase. Finally, high-purity laurolactam may be purified, which is preferred.

[0050] The evaporation may be performed in a film evaporator, but the present invention is not limited thereto.

[0051] On the other hand, a thin film evaporator is an evaporation device used in the process of obtaining a high-purity desired substance from a mixed substance (liquid) through a distillation reaction. That is, by forming a liquid mixture into a very thin film (film) through physical force, the surface area of ​​the mixture is maximized, thereby increasing the evaporation rate and separating substances with high purity.

[0052] Furthermore, the present invention can provide a laurolactam synthesis device for executing the above-mentioned method for preparing laurolactam. In this case, the substances, reaction conditions, etc. used due to the technical concept that is substantially the same as that mentioned in the above-mentioned method for preparing laurolactam should be interpreted as being substantially the same as the above-mentioned content.

[0053] Hereinafter, another example of the laurolactam synthesis apparatus will be described.

[0054] The laurolactam synthesis device of the present invention comprises: a first reactor, in the presence of a catalyst system, cyclododecanone oxime is synthesized into laurolactam by Beckmann rearrangement reaction; an evaporator, removing the solvent of the laurolactam synthesized in the first reactor; a second reactor, mixing the laurolactam from which the solvent is removed in the evaporator with a good solvent and removing the catalyst system; and a third reactor, mixing the laurolactam from which the catalyst system is removed in the second reactor with a poor solvent for recrystallization.

[0055] The laurolactam synthesis device may further include a filter for removing the solid catalyst system precipitated in the second reactor.

[0056] The laurolactam synthesis device may further include a film evaporator for separating high molecular weight substances (Heavies) from the recrystallized laurolactam.

[0057] The "reactor", "(film) evaporator" and "filter" mentioned in the present invention may use various known reactors, (film) evaporators and filters, and their specifications and sizes may be appropriately adjusted according to the scale and environment of the process, and are therefore not limited. In addition, various inlet pipes, outlet pipes, etc. may be provided for allowing substances to flow in or out of each reactor, (film) evaporator and filter, and various devices for adjusting the inflow and outflow amounts and various devices for controlling the use of various devices are matters that can be appropriately adjusted by a person skilled in the art of the present invention.

[0058] Hereinafter, another example is provided to provide a laurolactam composition synthesized by the above-mentioned preparation method of laurolactam.

[0059] The laurolactam composition can achieve a conversion rate of cyclododecanone oxime of 98% to 99%, preferably 99% to 99.5%, more preferably 99.5% to 99.9%, and a selectivity of laurolactam of 97% to 98%, preferably 98% to 99%, more preferably 99% to 99.5%.

[0060] Furthermore, the laurolactam composition may contain a catalyst system for Beckmann rearrangement reaction in an amount of 5 weight percent or less, preferably less than 5 weight percent, more preferably less than 3 weight percent, and most preferably less than 1 weight percent or less than 0.5 weight percent, relative to the total weight of the laurolactam composition. If the amount of the catalyst system exceeds the content range, the activity of the anion initiator used in the anion polymerization will be significantly reduced, and thus the polymerization reaction will not be easy to proceed.

[0061] On the other hand, the content of the catalyst system contained in the laurolactam composition can be measured by an inductively coupled plasma emission spectrometer (ICP, Inductively Coupled Plasma Spectrometer) analyzer.

[0062] Hereinafter, another example of the present invention provides a method for preparing polylaurolactam, and the preparation method may include the following steps: performing anionic polymerization on the laurolactam composition in the presence of an anionic initiator.

[0063] The polymerization of the purified laurolactam and any new monomer (comonomer) can be carried out at a temperature of 200° C. to 350° C. for 10 to 60 minutes. Specifically, the polymerization reaction is carried out at a temperature of 200° C. to 300° C., preferably at a temperature of 220° C. to 250° C., for 10 to 60 minutes, preferably 10 to 50 minutes, and more preferably 20 to 40 minutes.

[0064] The polymerized polylaurolactam may be a polymer containing laurolactam, for example, may be a copolyamide or a polyether-block amine, and preferably, may be polylaurolactam 12 (nylon 12).

[0065] The anion initiator may include one or more selected from the group consisting of NaH, LiH, KH and n-BuLi. The catalyst system material for Beckmann rearrangement reaction of one embodiment of the present invention can significantly reduce the activity of the anion initiator, but the preparation method of laurolactam according to one embodiment of the present invention and the laurolactam composition prepared thereby can effectively remove the catalyst system material, so that the laurolactam monomer can be anion polymerized with a high degree of polymerization under the anion initiator.

[0066] The anionic polymerization may be performed in a batch reactor or a continuous reactor (CSTR, PFR or PBR), preferably in a continuous reactor, but the present invention is not limited thereto.

[0067] The weight average molecular weight of the polymerized polylaurolactam may be greater than 6,000, preferably 6,500 to 14,000, more preferably 8,000 to 12,000 or 9,000 to 11,000.

[0068] Hereinafter, the present invention will be described in detail by way of examples. However, this is for the purpose of describing the present invention in more detail, and the scope of protection claimed by the present invention is not limited to the following examples.

[0069] Example

[0070] Preparation Example 1

[0071] 3 g of cyclododecanone oxime, 12 g of isopropylcyclohexane, 0.045 g of cyanuric chloride, and 0.03 g of zinc chloride were placed in a 100 ml round-bottom flask. The temperature was adjusted to 95° C. using a heating mantle, and the reaction was stirred at 200 rpm or more. The reaction was completed in 5 minutes, the conversion rate of cyclododecanone oxime was 99% or more, and the selectivity of lauryl lactam was 99% or more.

[0072] Example 1

[0073] 100g of the product prepared by Preparation Example 1 was injected into the evaporator, and isopropylcyclohexane (IPCH) was removed from the top of the evaporator by distillation at 150°C. 700g of ethanol was injected into the generated brown solid (pre-purification laurolactam) to dissolve it in a flask. The floating solid (catalyst) was removed by a 0.22μm filter, and 1600g of water was injected into the laurolactam (LL) dissolved in ethanol to recrystallize into a laurolactam (LL) solid. The recrystallized laurolactam (LL) solid was separated using a filter, and a film evaporator was used to remove high molecular weight substances (Heavies) at the bottom, and laurolactam (LL) was separated at the top, and the residual catalyst content and the laurolactam (LL) yield were measured and recorded in Table 1.

[0074] Next, using the prepared laurolactam (LL), 50 g of laurolactam (LL) and a catalyst were added into a 100 ml round-bottom flask at a weight ratio of LL: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 a temperature of 240° C. for 30 minutes to prepare polylaurolactam 12 (PA12). The degree of polymerization of polylaurolactam 12 (PA12) is recorded in Table 1.

[0075] Example 2

[0076] Except for injecting 300 g of ethanol, the same method as in Example 1 was carried out to separate laurolactam (LL), and the residual catalyst content and the laurolactam (LL) yield were measured and recorded in Table 1, respectively.

[0077] Next, anionic polymerization was carried out in the same manner as in Example 1 to prepare polylaurolactam 12 (PA12). Table 1 shows the degree of polymerization of polylaurolactam 12 (PA12).

[0078] Example 3

[0079] Except that 700 g of water was injected into the laurolactam (LL) dissolved in ethanol, the laurolactam (LL) was separated in the same manner as in Example 1, and the residual catalyst content and the laurolactam (LL) yield were measured and recorded in Table 1, respectively.

[0080] Next, anionic polymerization was carried out in the same manner as in Example 1 to prepare polylaurolactam 12 (PA12). Table 1 shows the degree of polymerization of polylaurolactam 12 (PA12).

[0081] Comparative Example 1

[0082] 100 g of the product of Preparation Example 1 was injected into the evaporator, and isopropylcyclohexane (IPCH) was removed from the top of the evaporator by distillation at a temperature of 150° C. The generated brown solid was removed from the bottom by using a thin film evaporator to remove high molecular weight substances (Heavies), and laurolactam (LL) was separated from the top. The residual catalyst content and the yield of laurolactam (LL) were measured and recorded in Table 1.

[0083] Next, anionic polymerization was carried out in the same manner as in Example 1 to prepare polylaurolactam 12 (PA12). Table 1 shows the degree of polymerization of polylaurolactam 12 (PA12).

[0084] Comparative Example 2

[0085] Except that water was not injected into the laurolactam (LL) dissolved in ethanol, laurolactam (LL) was separated in the same manner as in Example 1, and the residual catalyst content and the laurolactam (LL) yield were measured and recorded in Table 1, respectively.

[0086] Next, anionic polymerization was carried out in the same manner as in Example 1 to prepare polylaurolactam 12 (PA12). Table 1 shows the degree of polymerization of polylaurolactam 12 (PA12).

[0087] *Residual catalyst content determination method

[0088] Since laurolactam is solid at room temperature, it is no different from the solid catalyst used in the synthesis, but when melted at 150°C, the catalyst will remain as a black solid, so it can be confirmed whether the solid catalyst remains. The catalyst remaining in the laurolactam prepared in Preparation Example 1 is measured by weight by separating it into a solid at high temperature, or by using a solvent that can dissolve laurolactam.

[0089] * Determination method of yield of laurolactam

[0090] The content (L1) of laurolactam was calculated by measuring 100 g of the product prepared in Preparation Example 1 by gas chromatography (GC), and the content (L2) of laurolactam obtained at the upper end of the film evaporator in Example 1 was measured to calculate the yield of laurolactam (L2 / L1×100%).

[0091] *Determination method of molecular weight (polymerization degree) of polylaurolactam 12 (PA12)

[0092] In the polymerization reactor where the anionic polymerization reaction was completed, the agitator Torque value was calculated, and the weight average molecular weight of polylaurolactam 12 (PA12) was calculated by inverse calculation of the above value.

[0093] Table 1

[0094]

[0095] Referring to Table 1, in Examples 1 to 3, the residual catalyst was actually removed, and the purified laurolactam was subjected to anionic polymerization reaction to prepare polylaurolactam 12 (PA12). However, compared with Example 3, Example 1, which purified laurolactam (LL) with the preferred good solvent and poor solvent weight ratio of the present invention, further improved the yield of laurolactam (LL). On the other hand, in Example 2, ethanol was added in an amount less than the amount of laurolactam before purification, and the laurolactam (LL) yield decreased as the laurolactam not dissolved in ethanol and the residual solid catalyst were removed together in the filter, and a substance formed by agglomerating laurolactam and a small amount of catalyst (500 ppm) was allowed to remain through the filter, and a low molecular weight (6000) polylaurolactam 12 (PA12) was prepared. In Comparative Example 1, the good solvent and the poor solvent of the present invention were not added, and laurolactam (LL) was purified only by an evaporator, so the activity of the anion initiator (NaH) of the anion polymerization reaction was reduced by the catalyst remaining in a high content in the purified laurolactam (LL) composition, and the polymerization of polylaurolactam 12 (PA12) could not be performed. In addition, in Comparative Example 2, an excess of ethanol was added compared to water, and part of laurolactam (LL) would not be precipitated in a solid form, but existed in a state dissolved in ethanol, and thus was entrained with ethanol in the evaporator, and the yield of laurolactam (LL) was significantly reduced, confirming that it was difficult to apply to commercial processes.

[0096] The present invention has been described above by specific matters and limited embodiments, but this is only used to help fully understand the present invention. The present invention is not limited to the above embodiments, and a person skilled in the art of the present invention can make various modifications and variations based on these descriptions. Therefore, the concept of the present invention is not limited to the described embodiments, and not only the scope of the attached invention claims belongs to the scope of the concept of the present invention, but also the same or equivalent variations as the scope of the invention claims also belong to the scope of the concept of the present invention.

Claims

1. A method for preparing laurolactam, characterized in that: include: Step a), synthesizing cyclododecanone oxime into laurolactam by Beckmann rearrangement reaction in the presence of a catalyst system; Step b), mixing the laurolactam synthesized in the above step a) with a good solvent and removing the above catalyst system; as well as Step c), mixing the laurolactam from which the catalyst system is removed in step b) into a poor solvent for recrystallization, In the Beckmann rearrangement reaction of the above step a), cyclododecanone oxime is synthesized into laurolactam by a catalyst system comprising cyanuric chloride and zinc chloride in a solvent comprising isopropylcyclohexane, and the above step a) further comprises the following steps: removing the above solvent by distilling the synthesized laurolactam, removing the catalyst system by utilizing the solubility difference between the above catalyst system and the good solvent for laurolactam in the above step b), and recrystallizing the laurolactam by utilizing the difference between the solubility of the above laurolactam in the good solvent and the solubility of the above laurolactam in the poor solvent in the above step c), the above good solvent is a C1 to C4 alcohol, and the above poor solvent is distilled water or deionized water, and the above good solvent and the poor solvent are injected at a weight ratio of 1:1.5 to 1:

3.

2. The method for preparing laurolactam according to claim 1, characterized in that: The good solvent and the poor solvent are miscible.

3. The method for preparing laurolactam according to claim 1, characterized in that: The method further comprises the step of removing high molecular weight substances in a liquid phase and / or a solid phase by evaporating the recrystallized laurolactam, and separating the laurolactam in a gas phase.

4. A laurolactam synthesis device, characterized in that: include: In the first reactor, cyclododecanone oxime is synthesized into laurolactam by Beckmann rearrangement reaction under the catalyst system; an evaporator for removing the solvent of laurolactam synthesized in the first reactor; A second reactor is used to mix the laurolactam from which the solvent is removed in the evaporator with a good solvent and remove the catalyst system; as well as In the third reactor, the laurolactam from which the catalyst system has been removed in the second reactor is mixed with a poor solvent for recrystallization. Wherein, the laurolactam is recrystallized by utilizing the difference between the solubility of the laurolactam in a good solvent and the solubility of the laurolactam in a poor solvent. In the first reactor, the Beckmann rearrangement reaction is carried out in a solvent comprising isopropylcyclohexane, and cyclododecanone oxime is synthesized into laurolactam by a catalyst system comprising cyanuric chloride and zinc chloride. The evaporator removes the solvent by distilling the synthesized laurolactam. The second reactor removes the catalyst system by utilizing the difference in solubility of the catalyst system and the good solvent for laurolactam. The good solvent is an alcohol of C1 to C4, and the poor solvent is distilled water or deionized water. The good solvent and the poor solvent are injected at a weight ratio of 1:1.5 to 1:

3.

5. The laurolactam synthesis device according to claim 4, characterized in that: The invention also comprises a filter for removing the catalyst system precipitated in the second reactor.

6. The laurolactam synthesis device according to claim 4, characterized in that: The invention also comprises a thin film evaporator for separating high molecular weight substances from the recrystallized laurolactam.

7. A method for preparing polylaurolactam, characterized in that: Step a), synthesizing cyclododecanone oxime into laurolactam by Beckmann rearrangement reaction in the presence of a catalyst system; Step b), mixing the laurolactam synthesized in the above step a) with a good solvent and removing the above catalyst system; Step c), mixing the laurolactam from which the catalyst system is removed in step b) into a poor solvent for recrystallization; as well as Step d), preparing polylaurolactam by anion polymerization of the recrystallized laurolactam composition in the presence of a negative ion initiator, In the Beckmann rearrangement reaction of the above step a), cyclododecanone oxime is synthesized into laurolactam by a catalyst system comprising cyanuric chloride and zinc chloride in a solvent comprising isopropylcyclohexane, and the above step a) further comprises the following steps: removing the above solvent by distilling the synthesized laurolactam, removing the catalyst system by utilizing the solubility difference between the above catalyst system and the good solvent for laurolactam in the above step b), and recrystallizing the laurolactam by utilizing the difference between the solubility of the above laurolactam in the good solvent and the solubility of the above laurolactam in the poor solvent in the above step c), the above good solvent is a C1 to C4 alcohol, and the above poor solvent is distilled water or deionized water, and the above good solvent and the poor solvent are injected at a weight ratio of 1:1.5 to 1:

3.

8. The method for preparing polylaurolactam according to claim 7, characterized in that: The anion initiator includes one or more selected from the group consisting of NaH, n-BuLi, KH and LiH.

9. The method for preparing polylaurolactam according to claim 7, characterized in that: The anionic polymerization is performed at a temperature of 200° C. to 350° C. for 10 to 60 minutes.

10. The method for preparing polylaurolactam according to claim 7, characterized in that: The weight average molecular weight of the polymerized polylaurolactam is greater than 6,000.

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