Preparation method of isocyanate composition and isocyanate composition

Abstract

The invention provides a preparation method of a high-purity isocyanate composition and the isocyanate composition.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on and claims the priority of Korean Patent Application Nos. 10-2022-0100078 and 10-2023-0104263 filed on August 10, 2022 and August 9, 2023, respectively, the disclosures of which are incorporated herein by reference in their entirety.

[0003] The invention relates to a preparation method of a high-purity isocyanate composition and the isocyanate composition. Prior art

[0004] Isocyanate compounds are high-value compounds that are used not only in the chemical and resin industries but also as raw materials for fine chemicals (including optical materials). A representative example of isocyanate compounds is xylylene diisocyanate (hereinafter referred to as XDI), which is a raw material for high-end optical lenses and is in increasing demand as a high value-added chemical material.

[0005] Generally, isocyanates are prepared by a phosgenation method in which a raw material amine reacts with phosgene. At this time, the phosgenation reaction to form an aromatic isocyanate is an endothermic reaction, so it is necessary to continue heating and maintain a high temperature during the reaction to increase the yield of the desired product.

[0006] However, since isocyanates such as XDI generally have high reactivity with amino groups, side reactions occur in many cases, and impurities formed by the side reactions make it difficult to use isocyanates for fine chemicals in the field of optical materials requiring high purity.

[0007] Therefore, after the reaction, a purification process must be performed to obtain a highly purified desired product. However, in the purification step, additional by-products will be produced as the exposure time at high temperature increases, which leads to the problem of a decrease in the yield of the desired product. Therefore, it is necessary to study a purification method for improving the yield of the desired product. Summary of the invention

[0008] Technical issues

[0009] The invention provides a preparation method of a high-purity isocyanate composition and the isocyanate composition. In the preparation method, when phosgene is used to prepare isocyanate, a stabilizer is added in the purification step.

[0010] Technical Solution

[0011] The present invention provides a method for preparing an isocyanate composition, which comprises: a reaction step of preparing an isocyanate-containing composition by reacting an amine-based compound or a salt thereof with phosgene; and a purification step of separating the isocyanate from the composition, wherein the purification step is carried out in the presence of a stabilizer.

[0012] In addition, the present invention provides an isocyanate composition comprising isocyanate, an isocyanate oligomer and a stabilizer.

[0013] In addition, the present invention provides a polyisocyanate composition comprising a polyisocyanate formed by a polymerization reaction of the isocyanate composition of the present invention and a polyvalent thiol.

[0014] Furthermore, the present invention provides an optical article comprising the polyisocyanate composition of the present invention.

[0015] In the present invention, the terms "first", "second", etc. are used to describe various components, and these terms are used only to distinguish one component from other components.

[0016] Furthermore, the terms used in the present specification are only used to explain the exemplary embodiments and are not intended to limit the present invention.

[0017] Unless the context clearly means otherwise, a singular expression includes a plural expression.

[0018] It should be understood that the terms "comprising", "having" or "having" in this specification are only used to indicate the existence of implemented features, numbers, steps, components or their combinations, and do not exclude more than one different features, numbers, steps, components, their combinations or their additional possibilities.

[0019] Since the present invention can be variously modified and can have various forms, specific embodiments are specifically illustrated and described below. However, this is not intended to limit the invention to the specific disclosed form. On the contrary, it is intended to include all changes, equivalents or substitutes within the scope of the concept and technology of the present invention.

[0020] In the present specification, the isocyanate-containing composition refers to a mixture containing isocyanate prepared by reacting an amine-based compound or a salt thereof with phosgene, unreacted raw materials, by-products, other stabilizers, and the like.

[0021] The present invention provides a method for preparing an isocyanate composition, the method comprising: a reaction step of preparing an isocyanate-containing composition by reacting an amine-based compound or a salt thereof with phosgene; and a purification step of separating the isocyanate from the composition, wherein the purification step is carried out in the presence of a stabilizer.

[0022] Generally, the preparation of isocyanates by phosgenation is carried out by reacting amines with phosgene, in which case monoisocyanates and the like are produced as by-products.

[0023] For example, in the case of xylene diisocyanate (XDI) as the isocyanate, when xylene diamine and phosgene are subjected to a phosgenation reaction, the phosgene reacts with the amino group of the amine to release hydrogen chloride and form carbamoyl chloride.

[0024] The carbamoyl groups in the carbamoyl chloride formed react to form isocyanate groups while further releasing hydrogen chloride, thereby forming xylene diisocyanate.

[0025] After the reaction is complete, the hydrogen chloride produced and the remaining phosgene are generally removed by distillation together with an inert gas, whereby they are separated from the xylene diisocyanate produced.

[0026] At this time, since the amino group in the amine, ie, xylene diamine, has high reactivity, it causes a side reaction during synthesis. In particular, byproducts including monoisocyanates such as ethylbenzyl isocyanate (EBI) and chloromethylbenzyl isocyanate (CMBI) are generated by the side reaction.

[0027] There is no significant difference in boiling point and other physical properties between monoisocyanates and aromatic isocyanates (including xylene diisocyanate), and therefore, the purification step requires severe conditions, reduced pressure, and high-temperature distillation.

[0028] In addition, as the exposure time to high temperature increases in the purification step, various by-products such as dimers, trimers, etc. are further generated, which reduces the yield of the aromatic isocyanate.

[0029] Therefore, the present invention can prepare a high-purity isocyanate composition even if a high-temperature distillation step is performed under reduced pressure by suppressing the generation of by-products in the purification step.

[0030] The amine-based compound used in the present invention is not particularly limited as long as it is a compound with an amino group in the molecule. Specifically, it can be a compound containing a ring structure and an amino group in the molecule, and more specifically, it can be an amine with a 2-functional or more ring structure containing more than 2 amino groups in the molecule. The specific example of the amine-based compound can include one or more selected from phenylenediamine, 1,2-xylene diamine (o-xylene diamine), 1,3-xylene diamine (m-xylene diamine), 1,4-xylene diamine (p-xylene diamine), α, α, α', α'-tetramethylxylene diamine, toluene diamine, diphenylmethane diamine, 1,2-bis (aminomethyl) cyclohexane, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, 1,4-tetramethylene diamine, 1,5-pentamethylene diamine, 1,6-hexamethylene diamine, and isophorone diamine.

[0031] Among the amine-based compounds, xylene diamine (XDA) or its salt can show more excellent effect when applied to the isocyanate preparation method. Preferably, the amine-based compound or its salt can include one or more selected from m-xylene diamine, p-xylene diamine, o-xylene diamine and its salt. More specifically, it can be m-xylene diamine, p-xylene diamine or o-xylene diamine and XDA hydrochloride or XDA carbonate, and one or more compounds in these compounds can be used.

[0032] Meanwhile, in a method including a reaction step of one embodiment, a salt of an amine-based compound may be used to suppress a violent reaction with phosgene. The salt of the amine-based compound may be prepared in advance by a neutralization reaction of reacting the amine-based compound with anhydrous hydrochloric acid or carbonic acid before the above-mentioned reaction step. The neutralization reaction for forming the salt may be performed at a temperature corresponding to or lower than that of the reaction step. For example, the neutralization reaction may be performed at a temperature of 20° C. to 80° C.

[0033] In addition, according to one embodiment of the present invention, the above-mentioned reaction step may further comprise an organic solvent selected from a halogenated hydrocarbon-based organic solvent, an ester-based organic solvent, and a mixture thereof. The organic solvent may have a boiling point of 120° C. or more, more specifically, a boiling point of 120° C. to 250° C. When the reaction is carried out in a solvent having such a high boiling point, a high-purity isocyanate can be prepared in a high yield.

[0034] The halogenated hydrocarbon-based organic solvent may specifically be an aromatic halogenated hydrocarbon-based organic solvent, such as monochlorobenzene, 1,2-dichlorobenzene or 1,2,4-trichlorobenzene.

[0035] In addition, the ester-based organic solvent can be specifically a fatty acid ester, such as amyl formate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, methyl isoamyl acetate, methoxybutyl acetate, secondary hexyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, benzyl acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, ethyl acetate, butyl stearate, butyl lactate or amyl lactate, etc.; and aromatic carboxylic acid esters, such as methyl salicylate, dimethyl phthalate or methyl benzoate, etc.

[0036] More specifically, among the above-mentioned halogenated hydrocarbon-based organic solvent and ester-based organic solvent, the organic solvent may include at least one of an aromatic halogenated hydrocarbon-based organic solvent and an ester-based organic solvent having a boiling point of 120° C. or more or 120° C. to 250° C.

[0037] When the phosgenation reaction is carried out in an organic solvent as described above, the amine-based compound or its salt may be used at a concentration of 20% by volume or less. If the concentration of the amine-based compound or its salt is greater than 20% by volume, there is a risk of precipitation of a large amount of amine hydrochloride.

[0038] Meanwhile, according to one embodiment of the present invention, the reaction step may be performed at 100° C. to 200° C., preferably 120° C. to 150° C. When the reaction step is performed at a temperature below 100° C., the heat required for the reaction may be insufficiently supplied, and thus the reaction may not proceed or may proceed very slowly, and when the reaction is performed at a temperature above 200° C., the process stability may decrease due to the rapid reaction progress, and the generation rate of by-products may increase due to excessive side reactions.

[0039] At the same time, as mentioned above, in addition to isocyanate, the composition prepared by the above reaction steps also contains EBI, CMBI and other by-products, so an additional purification process is required to obtain the desired product isocyanate. Therefore, the present invention includes a purification step for separating isocyanate from the composition. The purification step can be, for example, distillation, but is not limited thereto, as long as it is a possible purification method.

[0040] Meanwhile, the distillation of isocyanate is usually carried out at high temperature, and the boiling points of isocyanate and its byproducts are similar, and there is a high possibility of generating additional byproducts during distillation at high temperature. In addition, as the exposure time to high temperature increases in the purification step, various byproducts such as dimers, trimers, etc. are further generated, which reduces the yield of isocyanate.

[0041] Therefore, during the long distillation process, there may be problems such as the generation of additional by-products due to the decomposition and side reactions of isocyanates, and discoloration such as coloration and white turbidity, etc. In addition, the higher the content of such by-products, the more discoloration occurs when manufacturing optical products based thereon.

[0042] According to one embodiment of the present invention, the purification step may be performed in the presence of a stabilizer.

[0043] As described above, when the purification step is performed in the presence of a stabilizer, the generation of additional by-products can be suppressed even if distillation is performed for a long time. The stabilizer is mixed with isocyanate in the purification step, thereby playing a role in suppressing the side reaction of isocyanate at high temperature through a free radical trapping reaction.

[0044] Meanwhile, when a stabilizer or the like is added in the reaction step, it plays a role in suppressing the generation of by-product monoisocyanate by promoting the positive reaction and suppressing the side reaction. In contrast, when the isocyanate purification step is carried out in the presence of a stabilizer after the reaction as in the present invention, it has the following unique effect: even at high temperatures, the reaction between isocyanates and other side reactions are minimized, thereby improving the yield.

[0045] In addition, some stabilizers may be limited in use because they are not easily mixed or dissolved by simply adding the stabilizer to the final product. However, when the stabilizer is included in the purification step as in the present invention, the solubility of the stabilizer increases, thereby allowing the use of various stabilizers, and the corresponding stabilizer remains even after the preparation is completed, thereby improving the storage stability of the finally prepared isocyanate composition.

[0046] As described above, in the present invention, the purification step is carried out in the presence of a stabilizer, thereby making it possible to improve process stability and contribute to improving the efficiency of the entire process by obtaining a high-purity isocyanate composition.

[0047] Meanwhile, according to one embodiment of the present invention, the stabilizer may include one or more selected from the group consisting of a phosphorus-based compound, a piperidine-based compound, and a sulfone-based compound.

[0048] The phosphorus-based compound may include phosphoric acid, phosphorous acid, phosphous acid, phosphonic acid and their esters, etc. Specific examples may include phosphoric acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, dibutyl phosphate, triphenyl phosphite, trinonylphenyl phosphite, phenylphosphinic acid, ethyl phosphate, bis(2-ethylhexyl)phosphate, 1,4-butylene diphosphonic acid, isopropyl phosphate, 3-phosphonopropionic acid, etc., and any one of them or a mixture of two or more thereof may be used.

[0049] The compound based on piperidine refers to a cyclic compound and its derivatives having heteroatoms in the molecular structure. The specific examples of the compound based on piperidine can include 2,2,6,6-tetramethylpiperidine-1-oxyl group (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl group (hereinafter referred to as 4-hydroxy TEMPO), 4-methoxy-2,2,6,6-tetramethylpiperidine 1-oxyl group (4-methoxy-TEMPO), 2,2,6,6-tetramethyl-4-benzyloxypiperidine 1-oxyl group (4-benzyloxy-TEMPO), or 4-acetylamino-2,2,6,6-tetramethylpiperidine 1-oxyl group (hereinafter referred to as 4-acetylamino TEMPO) etc., any one or a mixture of two or more thereof can be used. Specifically, it can be TEMPO, 4-hydroxy TEMPO or 4-acetylamino TEMPO, and any one or a mixture of two or more thereof can be used in these compounds.

[0050] The sulfone-based compound may include 4,4'-biphenyldisulfonic acid, methyl p-toluenesulfonate, dodecylbenzenesulfonic acid, p-toluenesulfonic acid, p-toluenesulfonic acid, p-toluenesulfonamide, benzenesulfonamide, methanesulfonamide, p-toluenesulfonyl isocyanate, and any one thereof or a mixture of two or more thereof may be used.

[0051] Furthermore, in addition to the above-mentioned phosphorus-based compound, piperidine-based compound, and sulfone-based compound, halogenated acetic acid, benzoyl chloride, sulfuric acid, sulfuric acid ester, ion exchange resin, chelating agent, and the like may be further included.

[0052] Meanwhile, the content of the stabilizer may be 50 ppm to 5000 ppm or less, preferably 100 ppm to 3000 ppm, or 300 ppm to 2500 ppm, or 500 ppm to 2000 ppm, based on the weight of the isocyanate composition. When the concentration is 50 ppm or less, it is difficult to determine the effect of the stabilizer, such as inhibiting the generation of by-products, and when it exceeds 5000 ppm, the effect of increasing the amount added is not great, and there is a problem of increased preparation cost due to additional purification, etc.

[0053] Meanwhile, according to one embodiment of the present invention, the reaction step or purification step may further include a side reaction suppressing additive. Specific examples of the side reaction suppressing additive may include 2,2,6,6-tetramethylpiperidine-1-oxyl group (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidinyl 1-oxyl group (4-hydroxy TEMPO), 4-acetylamino-2,2,6,6-tetramethylpiperidine 1-oxyl group (4-acetylamino TEMPO), etc., and any one or a mixture of two or more thereof may be used. If the material is added in the initial stage of the reaction step, the positive reaction is promoted and the side reaction is suppressed by eliminating the hydrogen of the amine or intermediate product carbamoyl chloride during the phosgenation reaction, thereby suppressing the production of the by-product monoisocyanate.

[0054] The purification step may be performed by a method generally used for purifying isocyanate compounds. In one embodiment, the purification step may be performed by reduced pressure distillation and / or thin film distillation using a distillation column.

[0055] As the distillation tower used in the vacuum distillation, a plate tower or a packed tower can be used without limitation. The number of theoretical plates of the distillation tower can be, for example, 2 or more, 5 or more, or 7 or more, and 60 or less, or 40 or less.

[0056] The temperature during the vacuum distillation is maintained at less than 180°C, specifically 100°C or more, or 130°C or more, and the pressure during the vacuum distillation may be 0.001 kPa or more, or 0.005 kPa or more, or 0.01 kPa or more, or 0.1 kPa or more, and 50 kPa or less, or 45 kPa or less, or 40 kPa or less. The temperature and pressure during the vacuum distillation refer to the bottom temperature of the distillation tower.

[0057] In addition, the temperature at the top of the tower during the reduced pressure distillation may be above 10°C, or above 20°C, and below 180°C, or below 160°C, and the pressure may be similar to the bottom pressure, and may be above 0.001 kPa, or above 0.005 kPa, or above 0.01 kPa, and below 50 kPa.

[0058] The thin film distillation can be performed using a thin film distillation apparatus having an evaporator, a condenser and a pressure reducing device. The rotation speed of the rotor of the thin film distillation apparatus can be 50 rpm or more, or 120 rpm or more, or 200 rpm or more, and 500 rpm or less, 400 rpm or less, or 350 rpm or less. The temperature during the thin film distillation is maintained at less than 200°C, for example, 100°C or more, or 110°C or more, and 190°C or less, or 180°C or less, or 170°C or less, and the pressure can be 0.001 kPa or more, and 50 kPa or less, 30 kPa or less, 10 kPa or less, or 1 kPa or less.

[0059] Under the reduced pressure distillation conditions and / or thin film distillation conditions as described above, the residence time of the purification step can be reduced and the purification efficiency can be improved, thereby obtaining a high-purity isocyanate compound.

[0060] Meanwhile, the purification step may be performed in multiple stages while changing the temperature and / or pressure conditions. For example, the purification step may be performed by steps including removing the solvent, removing the low-boiling impurities, and removing the oligomers.

[0061] Specifically, the purification step may be performed at a temperature lower than 180° C., or at a temperature of 120° C. to 170° C., and at a pressure of 0.001 kPa to 50 kPa, wherein reduced pressure distillation for removing the solvent is performed at a first temperature and a first pressure, then low boiling point impurities are removed at a second temperature and a second pressure, and then high boiling point impurities are removed at a third temperature and a third pressure using a thin film distillation apparatus. At the same time, the order of the above purification steps may be changed.

[0062] Furthermore, before the reduced pressure distillation step, a nitrogen bubbling step may be further performed to remove unreacted phosgene and hydrogen chloride gas inside the reactor where the phosgenation reaction is completed.

[0063] Meanwhile, the final isocyanate composition obtained through the purification step may contain the stabilizer of the present invention used in the purification step, as well as a side reaction inhibitor, an isocyanate oligomer, etc. wherein the stabilizer is partially removed during the purification process, or may contain residual stabilizer or additives that are not removed, and the final isocyanate may contain less than about 99% or less than about 95% of the added amount of the stabilizer or additive.

[0064] Therefore, the present invention provides an isocyanate composition comprising an isocyanate, an isocyanate oligomer and a stabilizer.

[0065] According to one embodiment of the present invention, based on the weight of the isocyanate composition, the content of any one or more of P and S derived from the stabilizer may be 2000ppm or less. Meanwhile, regarding the type and function of the stabilizer, reference may be made to the above content. In other words, the isocyanate composition of the present invention comprises a stabilizer in a predetermined content range, thereby preventing isocyanate from being converted into isocyanate oligomers, and thus has excellent preservation / storage stability.

[0066] Preferably, based on the weight of the isocyanate composition, the content of any one or more of P and S derived from the stabilizer or additive may be 1800 ppm or less, 1500 ppm or less, 1200 ppm or less, 1000 ppm or less, 800 ppm or less, 500 ppm or less, or 400 ppm or less, and 10 ppm or more, 20 ppm or more, 30 ppm or more, or 35 ppm or more.

[0067] Meanwhile, the content of any one or more of P and S derived from the stabilizer can be measured by methods such as inductively coupled plasma-atomic emission spectroscopy (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), etc., which will be described in detail in the following embodiments. For example, P can be derived from the above-mentioned phosphorus-based compounds, and S can be derived from sulfone-based compounds, respectively.

[0068] In addition, based on the weight of the isocyanate composition, the isocyanate composition according to an embodiment may include the stabilizer in an amount of 50 to 3000ppm. As previously mentioned, the stabilizer portion is included in the final isocyanate composition to form the isocyanate composition. In addition, the content of the stabilizer can be calculated by measuring the content value of the element derived from the stabilizer in the above-mentioned isocyanate composition. Preferably, based on the weight of the isocyanate composition, the stabilizer can be included in an amount of more than 100ppm, more than 200ppm, more than 300ppm, or more than 400ppm, and less than 3000ppm, less than 2500ppm, or less than 2000ppm.

[0069] Meanwhile, the type of the stabilizer can refer to the description in the above-mentioned isocyanate preparation method. For example, the stabilizer can include one or more selected from pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, dibutyl phosphate, methyl p-toluene sulfonate, 4-dodecylbenzenesulfonic acid, p-toluenesulfonic acid, p-toluenesulfonamide, and benzenesulfonamide.

[0070] Meanwhile, the isocyanate composition of the present invention may include a stabilizer as described above. At this time, the stabilizer may be added at any step during the preparation step of the isocyanate composition, for example, before and / or after the isocyanate purification step, or during the purification step. When added during the purification step, as described above, the isocyanate composition of the present invention may be prepared according to the following preparation method, which comprises: a reaction step of preparing an isocyanate-containing composition by reacting an amine-based compound or a salt thereof with phosgene; and a purification step of separating isocyanate from the composition, wherein the purification step is performed in the presence of a stabilizer.

[0071] In addition, the isocyanate composition according to one embodiment has an isocyanate oligomer content of 2% or less based on the weight of the isocyanate composition after being stored at 5°C for 100 days. Preferably, after being stored at 5°C for 100 days, the oligomer content is 1.9% or less, 1.8% or less, or 1.7% or less based on the weight of the isocyanate composition. Meanwhile, the "oligomer" refers to a material prepared from isocyanate and / or by-products after the purification step, for example, a material having a molecular weight of about 600 g / mol to about 2000 g / mol formed by their combination. Meanwhile, the theoretical lower limit of the oligomer content in the isocyanate is 0wt%, but due to the combination between isocyanates, isocyanates with high reactivity also generate oligomers during the preparation process or during storage, such as dimers or trimers, for example, which may be 0.01wt% or more, 0.05wt% or more, 0.1wt% or more, or 0.5wt% or more. The specific analysis method of the oligomer will be described in detail in the following embodiments.

[0072] Furthermore, the present invention provides a polyisocyanate composition comprising a polyisocyanate formed by a polymerization reaction of the isocyanate composition of the present invention and a polythiol.

[0073] The polythiol is a compound containing two or more thiol groups (-SH) in the molecule, and specifically may be a compound having two or more, or three or more and eight or less, or five or less thiol groups in the molecule. The polythiol may be, for example, 2,3-bis(2-sulfanyl ethyl sulfanyl)propane-1-thiol.

[0074] The polymerization reaction is carried out by a thiourethane reaction between the isocyanate compound in the isocyanate composition and the thiol group in the polythiol. The polymerization reaction can be carried out under normal pressure and an inert gas atmosphere such as nitrogen, argon, etc. In addition, the polymerization reaction can be carried out in the presence of a catalyst or in the absence of a catalyst. As a result of the polymerization reaction, a polyisocyanate is prepared, and the polyisocyanate composition containing the polyisocyanate can further contain additives such as an internal release agent, an ultraviolet absorber, a polymerization initiator, a heat stabilizer, a color corrector, a chain extender, a crosslinker, a light stabilizer, a filler, and a photosensitizer as needed.

[0075] In addition, the present invention provides a product, which comprises the above-mentioned polyisocyanate composition. The product can be an optical material product, specifically an optical product, such as eyeglass lenses, camera lenses, plastic lenses, prisms, etc.

[0076] Beneficial Effects

[0077] According to the method for preparing an isocyanate composition of the present invention, an isocyanate composition having high purity and improved storage properties can be prepared by suppressing thermal denaturation and generation of by-products during a purification process. DETAILED DESCRIPTION

[0078] Hereinafter, the functions and effects of the invention will be described in more detail with reference to specific exemplary embodiments of the invention. However, these exemplary embodiments are provided only to illustrate the invention, and the scope of the invention is not limited thereto.

[0079] <Example>

[0080] Example 1

[0081] 1,2-Dichlorobenzene (471 g) and m-xylenediamine (XDA, 32.5 g) were placed in a flask, and anhydrous hydrochloric acid was injected at a rate of 20 g / hr at room temperature (23±5° C.) while stirring.

[0082] While injecting anhydrous hydrochloric acid, the temperature was raised to 50°C. After 4 hours of injection, the formed salt was cooled to room temperature, phosgene (43 g) was introduced into the reactor, and the reactor temperature was heated to 130°C.

[0083] From the moment of phosgene injection to the end of the reaction, a dry ice-acetone cooler was used to prevent phosgene from leaking to the outside.

[0084] After the reactor temperature reached 130° C., the reactor temperature was maintained at 125 to 135° C. for 2 hours to make the reaction solution transparent. After the solution became transparent, the inside of the reactor was cooled to 80° C. while introducing nitrogen.

[0085] The solvent was removed from the reaction solution from which phosgene was removed by distillation under reduced pressure, and bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite (1000 ppm based on the weight of the isocyanate composition) was added to a reactor, and the product was distilled at 150° C. using a thin film distillation apparatus having a rotor rotating at 200 rpm under 0.1 kPa to remove high boiling impurities, thereby preparing an isocyanate composition containing m-XDI.

[0086] Example 2

[0087] An isocyanate composition containing m-XDI was prepared in the same manner as in Example 1, except that dibutyl phosphate (1000 ppm) was added instead of bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite.

[0088] Example 3

[0089] An isocyanate composition containing m-XDI was prepared in the same manner as in Example 1, except that trinonylphenyl phosphite (1000 ppm) was added instead of bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite.

[0090] Example 4

[0091] An isocyanate composition containing m-XDI was prepared in the same manner as in Example 1, except that benzenesulfonamide (1000 ppm) was added instead of bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate.

[0092] Example 5

[0093] An isocyanate composition containing m-XDI was prepared in the same manner as in Example 1, except that p-toluenesulfonamide (2000 ppm) was added instead of bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate.

[0094] Example 6

[0095] An isocyanate composition containing m-XDI was prepared in the same manner as in Example 1, except that p-toluenesulfonamide (500 ppm) was added instead of bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate.

[0096] Example 7

[0097] An isocyanate composition containing m-XDI was prepared in the same manner as in Example 1, except that 1,2-dichlorobenzene (471 g), m-xylenediamine (XDA, 32.5 g) and 4-hydroxy-2,2,6,6-tetramethylpiperidinyl 1-oxyl (4-hydroxyTEMPO, 0.24 g) were placed in a flask and anhydrous hydrochloric acid was injected at a rate of 20 g / hr at room temperature (23±5° C.) while stirring to prepare a salt.

[0098] Comparative Example 1

[0099] An isocyanate composition containing m-XDI was prepared in the same manner as in Example 1, except that bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate was not added in the purification step.

[0100] Comparative Example 2

[0101] An isocyanate composition containing m-XDI was prepared in the same manner as in Example 7, except that bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate was not added in the purification step.

[0102] <Experimental example>

[0103] (1) XDI purity

[0104] The isocyanate compositions prepared in the examples and comparative examples were analyzed using GC. The GC used in the analysis was HP-6890, and FID was used for detection. The chromatographic column used was DB-17 (30m*0.25mm*0.5μm), the carrier gas was nitrogen (1.0mL / min), and the oven temperature was 80°C->5°C / min->160°C (8min)->20°C / min->280°C (18min).

[0105] (2) Loss rate (%)

[0106] For the isocyanate compositions prepared in the examples and comparative examples, the loss rate was determined according to the following Formula 1 using the weight of m-XDI before thin film distillation and the weight of m-XDI obtained after thin film distillation.

[0107] [Formula 1]

[0108] Loss rate (%) = 100 - [(weight of m-XDI after thin film distillation / weight of m-XDI before thin film distillation) x 100]

[0109] (3) Analysis of the content of elements derived from stabilizers

[0110] Sample preparation for ICP-AES analysis

[0111] 0.3 g of the sample and 5 ml of HNO3 were placed in a quartz vial and heated at 240°C for 30 minutes using Multiwave 7000 to obtain a clear solution, which was then massed up to 40 mL using DIW in a falcon tube and analyzed. The dilution rate of the sample was about 130 times.

[0112] Calibration curve creation

[0113] Use P, S standard solution (1000ug / ml metal, in H2O) from SCP Science as the standard for making the calibration curve of P, S elements. Use ICP-AES to measure the standard solution prepared by diluting reagent blank (Reagent blank) and ICP / AES standard solution, with the concentration of about 0.08ppm to about 10ppm of P element, and the concentration of about 0.4ppm to about 10ppm of S element to prepare the calibration curve. At this time, as the characteristic wavelength of P and S elements, 214.914nm and 181.975nm are selected respectively, and the correlation coefficient (correlation coefficient) of the calibration curve is confirmed to be more than 0.999. After analyzing the sample, the intensity (intensity) for each element wavelength is substituted into the calibration curve to calculate the content value, and the content value is multiplied by the dilution rate to calculate the final result value (ppm). In addition, the stabilizer content in the isocyanate composition is calculated based on the above-mentioned result value.

[0114] (4) Oligomer content (%)

[0115] The oligomer content of the isocyanate composition was measured by the following method.

[0116] First, the isocyanate compositions prepared in the examples and comparative examples were stored at 5° C. for 100 days, and then each isocyanate composition was subjected to gel permeation chromatography (GPC) analysis under the following conditions to obtain a molecular weight distribution curve (GPC curve) of the isocyanate composition, and the area of ​​the portion corresponding to the oligomer in the entire area of ​​the GPC molecular weight distribution curve was expressed as a percentage. Specifically, the oligomer content (area %) was calculated according to the following formula 2.

[0117] [Formula 2]

[0118] Oligomer content (%) = [B / A] X 100

[0119] In formula 2,

[0120] A represents the total area under the curve in the molecular weight distribution curve (GPC curve) of the isocyanate composition, and B represents the peak area corresponding to the oligomer in the molecular weight distribution curve of the isocyanate composition.

[0121] The total area of the GPC curve and the area of the part corresponding to the oligomer are obtained by integration respectively. At this time, the oligomer is evaluated based on a polymer having a weight average molecular weight (Mw) value of 600 g / mol to 2000 g / mol, and the part corresponding to the oligomer in the GPC curve is 19.42 ≤ log Mw ≤ 22.18.

[0122] <GPC analysis conditions>

[0123] Instrument used: Waters 2988

[0124] Chromatographic columns: Shodex KF-801, KF-802, KF-803 300 mm

[0125] Sample concentration: 1 wt / vol%, prepared by dissolving 0.1 mg of the sample in 9.9 ml of tetrahydrofuran

[0126] Carrier: THF

[0127] Detection method: UV

[0128] Flow rate: 1.0 ml / minute

[0129] Column temperature: 40 °C

[0130] Molecular weight when preparing the calibration curve: Use polystyrene with a molecular weight of 1000 g / mol to 20000 g / mol.

[0131] (5) Degassing time during lens manufacturing

[0132] Manufacturing lenses

[0133] Put the respective isocyanate compositions (41.6 g), zelec UN (manufactured by Stepan, 0.08 g), and biosorb 583 (manufactured by Sakai Chemical Industry Co., Ltd., 0.08 g) prepared in the examples and comparative examples into a flask, and stir and mix at room temperature for about 20 minutes to prepare a polyisocyanate.

[0134] After visually confirming that each component is sufficiently mixed with the polyisocyanate, add dibutyltin chloride (0.004 g) as a catalyst and stir and mix for 10 minutes.

[0135] To the obtained mixture, 2,3-bis(2-mercaptoethylthio)propane-1-thiol (38.4 g) was added, degassed under 5 mbar, and stirred for a predetermined time to prepare a polymerizable composition.

[0136] The polyisocyanate composition was filtered through a 1 μm polytetrafluoroethylene (PTFE) filter and then injected into a mold made of a glass mold and adhesive tape. The mold was placed in an oven, and the temperature of the oven was gradually increased from 10° C. to 120° C., and the polymerization reaction was carried out for about 20 hours.

[0137] After the polymerization was completed, the mold was taken out of the oven and demolded to obtain a plastic lens. The obtained lens was annealed at 120° C. for 6 hours.

[0138] Measuring degassing time

[0139] In the lens manufacturing process, the polyisocyanate polymerization composition was degassed at 5 mbar, and the time (min) required from the start of degassing to the point where bubbles were no longer generated was measured, and the effect of improving workability was evaluated based on the result.

[0140] [Table 1]

[0141]

[0142] 【1】*Area % in GC analysis

[0143] **Not Detected

[0144] As can be seen from Table 1, when the distillation step is performed by adding a stabilizer, a high-purity isocyanate composition is obtained, and it can be confirmed that by reducing the amount of XDI loss before and after the thin film distillation, a high-purity isocyanate composition with improved productivity can be prepared. It can also be confirmed that the isocyanate composition containing the corresponding stabilizer has improved storage stability due to reduced oligomer formation even when stored for a long time, and reduces the degassing time during lens production, thereby obtaining an effect of improving workability.

Claims

1. A method for preparing an isocyanate composition, the method comprising: a reaction step of preparing a composition containing an isocyanate by reacting an amine-based compound or a salt thereof with phosgene; and a purification step to separate the isocyanate from the composition, in, The purification step is carried out in the presence of a stabilizer.

2. The method according to claim 1, wherein: The amine-based compound or its salt comprises one or more selected from phenylenediamine, 1,2-xylenediamine, 1,3-xylenediamine, 1,4-xylenediamine, α,α,α',α'-tetramethylxylenediamine, toluenediamine, diphenylmethanediamine, 1,2-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, isophoronediamine and salts thereof.

3. The method according to claim 1, before the reaction step, further comprising: A step of forming a salt of an amine-based compound by reacting the amine-based compound with hydrochloric acid or carbonic acid.

4. The method according to claim 1, wherein: The reacting step is performed in the presence of an organic solvent selected from the group consisting of a halogenated hydrocarbon-based organic solvent, an ester-based organic solvent, and a mixture thereof.

5. The method according to claim 1, wherein: The reaction step is carried out at 100°C to 200°C.

6. The method according to claim 1, wherein: The stabilizer includes one or more selected from the group consisting of a phosphorus-based compound, a piperidine-based compound, and a sulfone-based compound.

7. The method according to claim 1, wherein: The stabilizer comprises one or more selected from pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, dibutyl phosphate, methyl p-toluenesulfonate, 4-dodecylbenzenesulfonic acid, p-toluenesulfonic acid, p-toluenesulfonamide and benzenesulfonamide.

8. The method according to claim 1, wherein: The stabilizer is contained in an amount of 50 ppm to 5000 ppm or less based on the weight of the isocyanate composition.

9. The method according to claim 1, wherein: The reaction step or the purification step further comprises one or more selected from 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-hydroxyTEMPO) and 4-acetylamino-2,2,6,6-tetramethylpiperidin-1-oxyl (4-acetylaminoTEMPO).

10. The method according to claim 1, wherein: The purification step is carried out by distillation at 100°C to 170°C.

11. The method according to claim 1, wherein: The purification step is carried out by distillation at 0.001 kPa to 50 kPa.

12. The method according to claim 1, wherein: The purification step further comprises the step of removing the solvent before adding the stabilizer.

13. An isocyanate composition comprising isocyanate, an isocyanate oligomer and a stabilizer.

14. The isocyanate composition according to claim 13, wherein The content of any one or more of P and S derived from the stabilizer is 2000 ppm or less based on the weight of the isocyanate composition.

15. The isocyanate composition according to claim 13, wherein The stabilizer is included in an amount of 50 ppm to 3000 ppm based on the weight of the isocyanate composition.

16. The isocyanate composition according to claim 13, wherein The stabilizer comprises one or more selected from pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, dibutyl phosphate, methyl p-toluenesulfonate, 4-dodecylbenzenesulfonic acid, p-toluenesulfonic acid, p-toluenesulfonamide and benzenesulfonamide.

17. The isocyanate composition according to claim 13, wherein After storage at 5° C. for 100 days, the content of the isocyanate oligomer is 2% or less based on the weight of the isocyanate composition.

18. A polyisocyanate composition comprising a polyisocyanate formed by a polymerization reaction of the isocyanate composition according to claim 13 and a polythiol.

19. An optical article comprising the polyisocyanate composition according to claim 18.

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