Isophorone diisocyanate composition with moderate reactivity with alcohols

Abstract

The present invention relates to an isophorone diisocyanate composition (IPDI) and its application. The isophorone diisocyanate composition contains 0.0005% to 0.0400% demethylated isophorone diisocyanate (H-IPDI). The IPDI provided by the present invention has moderate reactivity when reacting with alcohols, resulting in a reaction solution with lower color and turbidity and less residual monomers.

Description

Technical Field

[0001] The present invention provides an isophorone diisocyanate composition having moderate reaction activity with alcohols. Background Art

[0002] Isophorone diisocyanate (IPDI), a colorless or light yellow liquid at room temperature, is both an aliphatic and alicyclic isocyanate. It has lower reactivity and vapor pressure than aromatic isocyanates, and is less toxic than other isocyanates. Because its structure lacks benzene rings, it exhibits excellent weather resistance and can be used to prepare high-end polyurethane materials with light stability, weather resistance, and outstanding mechanical properties, such as elastomers, aqueous polyurethane dispersions, and UV resins. IPDI can also self-polymerize to form multifunctional polyisocyanates, and coatings prepared with them dry quickly, making them ideal for automotive refinishing applications. These applications place stringent requirements on the various components and impurity levels of the IPDI monomer.

[0003] As environmental awareness grows, the market is increasingly concerned about VOC emissions during the use of isocyanate monomers. To reduce solvent emissions during use, CN94108263.6 employs a method that reacts isocyanate monomers with polyols to form prepolymers. Because the prepolymers have a relatively high molecular weight, they emit relatively low VOC emissions during use, making this solution increasingly popular in the market.

[0004] As for IPDI, due to the difference in activity between its two NCOs, the more active NCO participates in the reaction with the polyol in the early stage, while the less active NCO participates in the reaction in the later stage. However, in the later stage of the reaction, the viscosity of the system will gradually increase, and the dispersed mixing effect between IPDI and the polyol is poor, so the required reaction time is relatively long. On the other hand, the local molecular and energy aggregation caused by the increase in viscosity will lead to excessive polymerization reaction, resulting in turbidity of the reaction liquid.

[0005] To address this issue, DD151466A1 proposes a solution that conducts the reaction in a solvent. However, this requires a subsequent desolventizing operation and leaves some solvent in the prepolymer, emitting VOCs during subsequent use. CN94108263.6 employs a solution that controls the residual IPDI monomer to 2% to reduce the viscosity of the reaction system, thereby promoting the reaction between NCO and polyols. However, this residual IPDI also emits a certain amount of VOCs, making it a suboptimal solution from an environmental perspective. Alternatively, increasing the temperature can reduce viscosity, but prolonged exposure to high temperatures can increase the color of the IPDI monomer and prepolymer, affecting their performance in high-end applications. Similar issues can also arise with high-temperature separation.

[0006] Therefore, it is of great significance to develop an IPDI monomer with moderate activity, less residual monomer in the prepolymer after reaction with polyol, and lower turbidity and color number of the prepolymer. Summary of the Invention

[0007] In response to the above-mentioned problems existing in the prior art, the present invention aims to develop an isophorone diisocyanate composition with moderate reactivity with alcohols. After the reaction of this IPDI composition with polyols, the prepolymer contains less residual monomers and has low turbidity and color.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] An isophorone diisocyanate (IPDI) composition, wherein the content of demethylated isophorone diisocyanate (H-IPDI) is 0.0005-0.0400 wt%, preferably 0.0010-0.0200 wt%, more preferably 0.0020-0.0100 wt%.

[0010] The general structural formula of the demethylated isophorone diisocyanate (H-IPDI) is:

[0011]

[0012] wherein R1 and R2 are H or CH3, but are not CH3 at the same time;

[0013] The structure of the demethylated isophorone diisocyanate (H-IPDI) is more preferably the following structure:

[0014]

[0015] There are no specific requirements for the preparation method of the isophorone dicyanate composition of the present invention, and the isophorone dicyanate composition of the composition can be obtained by any achievable method in the prior art.

[0016] The present invention can be implemented through the following scheme:

[0017] Option 1: Add H-IPDI compounds to IPDI, or blend IPDI compositions with high H-IPDI concentrations with conventional IPDI.

[0018] Option 2: Adding H-IPDA compounds to IPDA and then performing phosgenation reaction to obtain the IPDI composition of the specifications described in the present invention;

[0019] In some embodiments of the present invention, Scheme 2 is adopted. Therefore, one of the methods for preparing the IPDI composition of the present invention limits the content of demethylated isophorone diamine (H-IPDA) in the raw material IPDA to be above 0.0005%, and the upper limit may be higher than 0.04%.

[0020] Because the dealkylated product H-IPDA is relatively easy to separate from IPDA, patent CN107304168A mentions a two-step method for separating IPDA. First, low-boiling-point components, including hydrogen, inert gases, ammonia, and low-boiling-point impurities, are separated in a first distillation (low-boiling-point component separation). Subsequently, pure isophorone diamine is obtained through a second purification step, such as separation of organic residues (high-boiling-point components) using a vacuum distillation column. During the IPDA purification process, H-IPDA is enriched and recovered in the oil phase of the light components. Therefore, the H-IPDA content in conventional IPDA is extremely low or even absent, which in turn results in extremely low or even absent H-IPDI content in conventional IPDI obtained through the subsequent phosgenation reaction.

[0021] Therefore, in some embodiments, an IPDA composition having an H-IPDA content higher than 0.04% can be blended with conventional IPDA to obtain an IPDA composition having an H-IPDA content of 0.0005-0.0400%, preferably 0.0010-0.0200%, more preferably 0.0020-0.0100%, which can then be further phosgenated to obtain an IPDI composition having an H-IPDI content of 0.0005-0.0400%, preferably 0.0010-0.0200%, more preferably 0.0020-0.0100%.

[0022] Alternatively, a method may be adopted in which a certain amount of H-IPDA is added to conventional IPDA to obtain an IPDA composition having an H-IPDA content greater than 0.04%, the IPDA composition is directly phosgenated to obtain an IPDI composition having an H-IPDI content greater than 0.04%, and then the IPDI composition is blended with conventional H-IPDI to obtain an IPDI composition having an H-IPDI content of 0.0005-0.0400%, preferably 0.0010-0.0200%, and more preferably 0.0020-0.0100%.

[0023] There may be other methods for controlling H-IPDI, which are not listed in the present invention. The above methods can be used in combination or individually, and the present invention does not limit the method for obtaining the IPDI composition.

[0024] The demethylated isophorone diisocyanate content in the isophorone diisocyanate composition of the present invention can be analyzed by gas chromatography. There are no specific requirements for this. For example, in some specific examples, the method used is: the sample is dissolved in a solvent (preferably dichloromethane) and then analyzed by gas chromatography, detected by a flame ion detector (FID), and quantitatively calculated by area normalization.

[0025] The present inventors have discovered that the IPDI composition provided by the present invention, containing at least 0.0005% H-IPDI, exhibits relatively moderate reactivity with polyols. It is speculated that the H-IPDI in the IPDI composition has one or more fewer methyl groups on the six-membered ring compared to conventional IPDI, resulting in a slightly higher NCO activity of the H-IPDI, making it more reactive with the polyol. The heat released by the initial reaction between the H-IPDI and the polyol further triggers the reaction between the two, improving the efficiency of the reaction and avoiding excessive monomer residues caused by inefficient reactions. However, when the H-IPDI content in the IPDI composition is too high, the initial heat released by the H-IPDI and polyol reaction can intensify or even lead to a runaway reaction. This can result in excessive viscosity and even turbidity in the alcohol-modified product, hindering the mixing of the IPDI and polyol, prolonging the reaction time, and even causing the reaction solution to have a higher color. Therefore, the present invention controls the H-IPDI content within 0.04%, thereby controlling the reaction efficiency of the IPDI composition and the polyol to be within an appropriate range.

[0026] Therefore, the present invention limits the H-IPDI content in the IPDI composition to 0.0005-0.0400%, preferably 0.0010-0.0200%, and more preferably 0.0020-0.0100%.

[0027] Compared with the prior art, the isophorone diisocyanate composition provided by the present invention has the following advantages:

[0028] 1. The IPDI composition provided by the present invention has moderate reactivity with polyols;

[0029] 2. The prepolymer obtained after the reaction has a lower color number and less residual monomers. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further illustrated below by specific embodiments. Those skilled in the art should understand that the embodiments are merely helpful for understanding the present invention and should not be construed as specific limitations of the present invention. The polypropylene glycol used in the examples is produced by Wanhua Chemical Group Co., Ltd. and has a specification of PPG-2000.

[0031] The content of demethylated isophorone diisocyanate (H-IPDI) in the isophorone diisocyanate composition was analyzed by gas chromatography, wherein the sample was dissolved in dichloromethane and then analyzed by gas chromatography, detected by a hydrogen ion flame detector (FID), and quantitatively calculated by an area normalization method.

[0032] The chromatographic conditions are as follows:

[0033] Carrier gas: purified and dried high-purity nitrogen (purity ≥ 99.999%);

[0034] Combustion gas: hydrogen (purity ≥ 99.999%), flow rate 40 mL / min;

[0035] Combustion-supporting gas: purified and dry air, with a flow rate of 400 mL / min;

[0036] Makeup gas: nitrogen, flow rate 30mL / min;

[0037] Column flow rate: 1.06 mL / min;

[0038] Split ratio: 30:1;

[0039] Column temperature (programmed temperature): 140°C for 0 min, increase the temperature to 220°C at 10°C / min, hold for 1 min, increase the temperature to 260°C at 5°C / min, hold for 0 min, increase the temperature to 280°C at 10°C / min, hold for 1 min;

[0040] Inlet temperature: 270°C;

[0041] Detector temperature: 290°C;

[0042] Injection volume: 0.2 μL.

[0043] The quantitative analysis of H-IPDA in IPDA of the present invention is carried out on gas chromatography, and the gas chromatography analysis conditions are as follows:

[0044] Chromatographic column: Agilent HP-5 (specifications: 30m*0.32mm*0.25mm); inlet temperature: 280℃; split ratio: 30:1; column flow rate: 1.5ml / min; column temperature: 100℃, hold for 0.5min, then increase to 260℃ at 15℃ / min and hold for 8min; detector temperature: 280℃; H2 flow rate: 35ml / min.

[0045] Example 1 Preparation of IPDI compositions with different H-IPDI contents

[0046] Step I: Synthesis of Isophorone Diamine Composition

[0047] The synthesis of IPDA was carried out by the method provided in patent CN109761855A in the following steps:

[0048] (1) Isophorone was fed into a preheater at a rate of 200 kg / h and preheated to a reaction temperature of 120° C., and then fed into the reactor and the operating conditions disclosed in Example 1 of CN103301799B with HCN and a basic catalyst sodium methoxide in a molar ratio of 2:1:0.003. The reaction was carried out at an absolute pressure of 1 MPa. After reacting for 25 minutes, isophoronenitrile (3-cyano-3,5,5-trimethylcyclohexanone, abbreviated as IPN) was obtained.

[0049] (2) reacting the above-obtained isophorone nitrile, ammonia and hydrogen in the presence of a catalyst, as follows:

[0050] a) reacting the isophoronenitrile obtained in step (1) with ammonia in a tubular reactor at 60° C.

[0051] The reaction was carried out under the conditions of temperature and absolute pressure of 15 MPa, with a molar ratio of ammonia to isophoronenitrile of 50:1 to obtain 3-cyano-3,5,5-trimethylcyclohexylimine;

[0052] b) in the presence of a hydrogenation catalyst, Raney cobalt, at a catalyst space velocity of 1.5 g 3-cyano-3,5,5-trimethylcyclohexanone / (ml catalyst / hour), hydrogen, NH3, and the 3-cyano-3,5,5-trimethylcyclohexylimine obtained in step a) are mixed and reacted in a 3% KOH-ethanol solution at a temperature of 80° C. and an absolute pressure of 18 MPa to obtain a product containing 3-aminomethyl-3,5,5-trimethylcyclohexylamine (IPDA for short) and 3-cyano-3,5,5-trimethylcyclohexylamine;

[0053] In step b), the mass ratio of KOH-ethanol solution to the added isophoronenitrile is 1:600, the molar ratio of NH3 to isophoronenitrile is 50:1, and the molar ratio of hydrogen to isophoronenitrile is 80:1;

[0054] c) in the presence of a hydrogenation catalyst, Raney cobalt, the space velocity of the catalyst being 1.8 g 3-cyano-3,5,5-trimethylcyclohexanone / (ml catalyst hour), with hydrogen, NH 3 and the product containing 3-aminomethyl-3,5,5-trimethylcyclohexylamine and 3-cyano-3,5,5-trimethylcyclohexylamine obtained in step b) are mixed and reacted in 3% acetic acid-ethanol solution, and the reaction is carried out under the condition of 120 ℃ temperature and absolute pressure of 18 MPa, and 3-cyano-3,5,5-trimethylcyclohexylamine is converted into 3-aminomethyl-3,5,5-trimethylcyclohexylamine.

[0055] In step c), the mass ratio of the acetic acid-ethanol solution to the IPN obtained in step 1) is 1:500, the molar ratio of hydrogen to the IPN obtained in step 1) is 30:1, and the molar ratio of ammonia to the IPN obtained in step a) is 50:1.

[0056] Step II: Preparation of isophorone diamine compositions with different H-IPDA contents: Purify the 3-aminomethyl-3,5,5-trimethylcyclohexylamine obtained in step I and adjust the H-IPDA (Formula 1, the same below) content therein. The specific steps are as follows:

[0057] a) Using the method provided by Chinese patent CN107304168A, isophorone diamine was purified to obtain a conventional IPDA composition, wherein the H-IPDA content was 0.0001%, and an oil phase of a light component was obtained.

[0058] b) distilling the oil phase of the light component obtained in step a) using a distillation tower with 15 plates and a bottom temperature of 160-200° C., collecting fractions at 160-185° C., and analyzing the fractions, which showed an H-IPDA content of 98.5% and an IPDA content of 1.5%.

[0059] c) adding the H-IPDA obtained in step b) to the conventional IPDA composition obtained in step a) to obtain IPDA compositions having H-IPDA contents of 0.0003%, 0.0008%, 0.0015%, 0.0040%, 0.0060%, 0.0080%, 0.0150%, 0.0300%, 0.0500%, and 0.1000%, respectively.

[0060] Step III: Preparation of isophorone diisocyanate compositions with different H-IPDI contents The conventional IPDA composition obtained in Step II (H-IPDA content: 0.0001%), as well as IPDA compositions with H-IPDA contents of 0.0003%, 0.0008%, 0.0015%, 0.0040%, 0.0060%, 0.0080%, 0.0150%, 0.0300%, 0.0500%, and 0.1000%, were reacted with phosgene to prepare IPDI compositions with different H-IPDI contents.

[0061] The specific method is as follows: using the heater described in Example 1 of Chinese Patent CN105214568A, the obtained IPDA is vaporized and heated to 355°C. Under the protection of nitrogen, the IPDA and the gaseous phosgene heated to 355°C are continuously added to the reactor through respective feed pipes for reaction. The reaction pressure is 0.05 MPa absolute pressure and the temperature is 360°C. The feed rate of IPDA is 800 kg / h and the feed rate of phosgene is 3000 kg / h. The mixed gas after the reaction is rapidly cooled to 100°C using an o-dichlorobenzene solution through a gas jet absorption device to obtain a photosynthetic liquid containing the product IPDI; excess phosgene is removed at 180°C and an absolute pressure of 0.1 MPa to obtain a crude IPDI product free of phosgene; and the crude product is then distilled in a distillation tower to obtain an IPDI composite product at a distillation range of 0.5 kPa and 150-160°C.

[0062] The obtained IPDI composite products were subjected to gas phase analysis, and the H-IPDI contents therein were 0.0001% (sample 1), 0.0003% (sample 2), 0.0008% (sample 3), 0.0015% (sample 4), 0.0040% (sample 5), 0.0060% (sample 6), 0.0080% (sample 7), 0.0150% (sample 8), 0.0300% (sample 9), 0.0500% (sample 10), and 0.1000% (sample 11).

[0063] Sample 11 was mixed with sample 1 to obtain sample 12. Gas phase analysis showed that the H-IPDI content was 0.0051% (sample 12).

[0064] Example 2 Evaluation of the reaction between IPDI composition and polyol

[0065] a) diluting the catalyst dibutyltin dilaurate (T12) with toluene to a concentration of 1% for later use;

[0066] b) Add 67.5 g of PPG-2000 with a moisture content of 300 ppm to a 500 ml reactor, place the reactor in an 82°C oil bath, and start stirring to preheat at 180 rpm.

[0067] c) After the temperature in the reactor reached 80° C., 0.3 g of the catalyst T12 prepared in step a) and 7.6 g of the IPDI composition were added to the reactor and reacted;

[0068] d) Samples were taken every 5 minutes during the reaction to monitor the NCO content. When the NCO content no longer decreased, the reaction was considered to have stopped, heating was stopped, and the reaction time was recorded.

[0069] e) After the temperature of the reactor was lowered to room temperature, a sample was taken and the reaction solution was analyzed by area normalization using GPC to obtain the residual monomer content, and the color value thereof was measured using the method of GB / T605-2006.

[0070] In the example, eight batches of IPDI compositions, namely samples 3, 4, 5, 6, 7, 8, 9 and 12, were tested to obtain different batches of reaction solutions.

[0071] Comparative Example 1

[0072] The same method as in Example 2 was adopted, but the IPDI compositions used were samples 1, 2, 10, and 11, which were tested separately to obtain different batches of reaction solutions.

[0073] Comparative Example 2

[0074] A certain amount of 3-isocyanatemethyl-5,5-dimethylcyclohexyl isocyanate was prepared by the method provided in patent JP2000044527A and added to sample 1 to obtain an IPDI composition (sample 13) with a 3-isocyanatemethyl-5,5-dimethylcyclohexyl isocyanate content of 0.008%.

[0075] The evaluation test was carried out according to the method provided in Example 2.

[0076] The H-IPDI content of the eight batches of samples in Example 2 and the five IPDI compositions in Comparative Examples 1 and 2, and the quality of the reaction solutions obtained by reacting them with polyols are as follows:

[0077] Note 1: Contains 0.008% of 3-isocyanatemethyl-5,5-dimethylcyclohexyl isocyanate.

[0078] The results in the table above show that the eight batches of isophorone diisocyanate compositions tested in Example 2 have moderate reactivity with polyols, and the resulting reaction solutions have low color and turbidity, and the residual monomer content is below 0.01%, which is a clear advantage over the comparative example.

[0079] While the present invention is described through the above-described embodiments, the present invention is not limited to the above-described detailed methods, nor does it necessarily rely on the above-described detailed methods for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for raw materials in the products of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. An isophorone diisocyanate composition, characterized in that The content of demethylated isophorone diisocyanate in the isophorone diisocyanate composition is 0.0008-0.03 wt %; The general structural formula of the demethylated isophorone diisocyanate is: The structures of R1 and R2 are H or CH3, but they are not CH3 at the same time.

2. The isophorone diisocyanate composition according to claim 1, wherein The content of demethylated isophorone diisocyanate in the isophorone diisocyanate composition is 0.0010-0.0200 wt %.

3. The isophorone diisocyanate composition according to claim 2, wherein The content of demethylated isophorone diisocyanate in the isophorone diisocyanate composition is 0.0020-0.0100 wt %.

4. The isophorone diisocyanate composition according to any one of claims 1 to 3, characterized in that The structure of the demethylated isophorone diisocyanate is as follows:

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