阅读说明：本技术 一种功能型降色剂以及稳定二异氰酸酯产品的色号的方法 (Functional color reducing agent and method for stabilizing color number of diisocyanate product ) 是由 金振宇 王树宾 张坤 张宏科 于 2019-12-05 设计创作，主要内容包括：本发明属于二异氰酸酯生产的技术领域,具体涉及一种功能型降色剂以及稳定二异氰酸酯产品的色号的方法,该功能型降色剂包括如下各组分：(a)受阻胺类物质,(b)受阻酚类物质和/或酯类物质。所述稳定二异氰酸酯产品的色号的方法为将所述功能型降色剂与二异氰酸酯混合,再经冷冻结晶和再溶化后成液体,得到APHA色号稳定的二异氰酸酯产品。本发明的方法可以避免二异氰酸酯产品冷冻结晶和再溶化过程中产生黄绿色盐类物质,实现二异氰酸酯产品的色号稳定性、保持产品冷冻结晶和再溶化后的低色号。(The invention belongs to the technical field of diisocyanate production, and particularly relates to a functional color reducing agent and a method for stabilizing the color number of a diisocyanate product, wherein the functional color reducing agent comprises the following components: (a) hindered amine substances, (b) hindered phenolic substances and/or ester substances. The method for stabilizing the color number of the diisocyanate product comprises the steps of mixing the functional color reducing agent with the diisocyanate, and freezing, crystallizing and re-melting the mixture to form liquid to obtain the diisocyanate product with stable APHA color number. The method can avoid the generation of yellow green salt substances in the processes of freezing, crystallizing and remelting the diisocyanate product, realize the color number stability of the diisocyanate product and keep the low color number of the product after freezing, crystallizing and remelting.)

1. A functional color reducing agent is characterized by comprising the following components:

(a) a hindered amine-type substance, wherein the hindered amine-type substance,

(b) hindered phenolic and/or ester species;

wherein the mass ratio of the component (a) to the component (b) is 1:1 to 5:1, preferably 1:1 to 3:1, and more preferably 2: 1.

2. The functional color-reducing agent according to claim 1, wherein the functional color-reducing agent is in a liquid state at room temperature, and has a viscosity of 500-2000 mPa-s (at 25 ℃), preferably of 1000-1500 mPa-s (at 25 ℃), and more preferably of 1200 mPa-s (at 25 ℃).

3. The functional color-reducing agent according to claim 1 or 2, wherein the molecular structure of the hindered amine-based substance is represented by formula (I):

R₂—NH—R₁，(I)

in the formula, R₁And R₂The structural groups are the same or different and are respectively and independently selected from the structural groups shown in the formulas (i) to (v);

preferably, R₁And R₂The same, more preferably a structural group represented by the formula (iv);

preferably, the hindered amine species is selected from one or more of 4,4 '-bis- (2,3, 3-trimethyl-1-butenyl) diphenylamine, 4' -bis (phenylisopropyl) diphenylamine, 4 '-di-tert-butyldiphenylamine and 4, 4' -di-sec-butyldiphenylamine, more preferably from 4,4 '-bis- (2,3, 3-trimethyl-1-butenyl) diphenylamine and/or 4, 4' -bis (phenylisopropyl) diphenylamine.

4. The functional color-reducing agent according to any one of claims 1 to 3, wherein the molecular structure of the hindered phenolic substance is represented by formula II:

R₄—HN—(CH₂)_n—NH—R₃，(II)

in the formula, R₃And R₄The structural groups are the same or different and are respectively and independently selected from the structural groups shown in the formulas (vi) to (vii); n is a positive integer, and the value of n is 1-8, preferably 4-8, and more preferably 6;

in the formulas (vi) to (vii), k is a natural number and has a value of 0 to 4, preferably 1 to 3, and more preferably 2;

preferably, R₃And R₄The same, more preferably a structural group represented by the formula (vi);

preferably, the hindered phenolic substance is selected from the group consisting of N, N '-bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) butanediamine, N' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) pentanediamine, N '-bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine, N' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) heptanediamine, N '-bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) octanediamine, N' -bis- (2- (3, one or more of 5-di-tert-butyl-4-hydroxyphenyl) acetyl) hexamethylenediamine and N, N '-bis- (4- (3, 5-di-tert-butyl-4-hydroxyphenyl) butyryl) hexamethylenediamine, and more preferably N, N' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexamethylenediamine.

5. The functional color-reducing agent according to any one of claims 1 to 4, wherein the molecular structure of the ester substance is represented by formula (III):

in the formula, R₅And R₆The structural groups are the same or different and are respectively and independently selected from the structural groups shown in the formulas (viii) to (ix); n is a positive integer, and the value of n is 1-8, preferably 4-8, and more preferably 8;

in the formulas (viii) to (ix), k is a natural number, and the value thereof is 0 to 2, preferably 0 to 1, and more preferably 0;

preferably, R₅And R₆The same; more preferably a structural group represented by formula (viii);

preferably, the ester is selected from one or more of bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) adipate, bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) pimelate, bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) suberate, bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) azelate, bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) sebacate and bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) sebacate, more preferably bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) sebacate.

6. A method for stabilizing the color number of a diisocyanate product, which is characterized in that the diisocyanate product with the APHA color number is obtained by mixing the diisocyanate with the functional color reducing agent as defined in any one of claims 1 to 5, and then freezing, crystallizing and re-melting the mixture into liquid;

preferably, the functional color reducing agent is added in an amount of 0.001 wt% to 0.2 wt%, more preferably 0.01 wt% to 0.08 wt%, and even more preferably 0.02 wt% to 0.04 wt% based on the weight of the diisocyanate.

7. The process according to claim 6, wherein the diisocyanate is selected from one or more of diphenylmethane diisocyanate, toluene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, 1, 5-naphthalene diisocyanate, hexamethylene diisocyanate, p-phenylene diisocyanate and 1, 4-cyclohexane diisocyanate, preferably selected from diphenylmethane diisocyanate and/or toluene diisocyanate, more preferably diphenylmethane diisocyanate.

8. The process according to claim 7, characterized in that the toluene diisocyanate has a 2, 4-isomer content of 65 to 99.5 wt.%, preferably 79 to 81 wt.%, based on the total weight of the toluene diisocyanate; and/or

The content of 4, 4-isomer in the diphenylmethane diisocyanate is 10 to 99.5 wt%, preferably 44.5 to 49 wt%, based on the total weight of the diphenylmethane diisocyanate.

9. The method according to any one of claims 6 to 8, wherein the temperature of the freeze crystallization is between-30 ℃ and 5 ℃, preferably between-18 ℃ and-10 ℃; the temperature of the re-melting is 60-80 ℃, preferably 70-75 ℃.

10. The process according to any one of claims 6 to 9, wherein the difference in APHA color number between before and after the freeze crystallization and resolubilization is no greater than # 3, preferably no greater than # 1.

Technical Field

The invention belongs to the technical field of diisocyanate production, and particularly relates to a functional color reducing agent and a method for stabilizing the color number of a diisocyanate product.

Background

Diisocyanate is generally prepared by condensation of amine as a raw material to prepare polyamine and then phosgenation of the polyamine. Therefore, the prepared diisocyanate basically contains acyl chloride substances and urea impurities. Research shows that in the process of low-temperature freezing crystallization of diisocyanate products, due to the change of a temperature field, contained acyl chloride substances and urea impurities gradually migrate to the core of a packaging barrel through pores of crystals to be enriched; and along with the increase of the concentration, the acyl chloride substances and the urea substances are combined with each other irreversibly to form salts, so that the diisocyanate crystal at the barrel core is yellow green, the whole barrel of liquid diisocyanate product after being dissolved is also yellow green, the color number is obviously increased, and the use is influenced.

The production process of diisocyanates is complicated and color-causing substances, such as aldehydes, ketones, chlorides and nitrogen-containing substances, are formed in ppm levels. There have been many processes for reducing the color number of diisocyanates (e.g., diphenylmethane diisocyanate MDI, toluene diisocyanate TDI, dicyclohexylmethane diisocyanate HMDI, isophorone diisocyanate IPDI, naphthalene 1, 5-diisocyanate NDI, hexamethylene diisocyanate HDI, p-phenylene diisocyanate PPDI, 1, 4-cyclohexane diisocyanate CHDI) so as to obtain a low color number diisocyanate product. These methods include the following aspects:

1. treatment or purification of the starting polyamine materials or oligomers thereof

For example, patent document EP0546398A discloses the acidification of polymethylene polyphenylene polyamines prior to phosgenation, followed by the production of isocyanate products of low color number.

For example, patent document EP446781A discloses a process in which polymeric MDA (monomeric and oligomeric polymethylene polyphenylene polyamines) are first treated with hydrogen and subsequently phosgenated to give a lighter color MDI.

For example, patent document CN 103319372A discloses a method for preparing light-colored or colorless dicyclohexylmethane diisocyanate (HMDI) by operations such as phosgenation, distillation, and rectification after controlling the content of alcohol compounds in dicyclohexylmethane diamine as a raw material to be less than 0.2%.

For example, patent document CN1356980A discloses a process for preparing isocyanates having a light color by first controlling the content of bromine or iodine-containing molecules or mixtures thereof in phosgene to less than 25ppm and then preparing isocyanates having a light color by phosgenating amines of the diphenylmethane diamine series or mixtures of a plurality of these amines with the above-mentioned phosgene.

2. Solution for researching color reduction in phosgenation process

For example, patent document US5364958A discloses that it is possible to prepare isocyanates having a light color by completely removing phosgene at low temperature after completion of the phosgenation reaction and subsequently treating the product while it is hot with HCl gas.

For example, patent document DE19817691.0 describes a process for preparing MDI/PMDI mixtures having a lower content of hydrogen chloride by-products and a lower iodine color value by optimizing the parameters in the phosgenation reaction.

3. After phosgenation and before separation and rectification treatment, the crude product containing isocyanate is added with color-reducing additive

For example, patent document EP0581100A discloses a process for preparing polyisocyanates in which a chemical reducing agent is added after phosgenation and before removal of the solvent to prepare a light-colored product.

For example, U.S. Pat. Nos. 4465639A, 538500A, EP0445602A and EP0467125A describe the addition of water, carboxylic acids, alkanols or polyether polyols, respectively, to the crude seed after the phosgenation for the purpose of reducing color.

4. The post-treatment stage of the final product is subjected to color reduction treatment

For example, EP0133528A discloses the extractive purification of isocyanates to give a light-colored MDI product.

For example, patent document EP0561225A discloses a process for preparing light-colored isocyanates or isocyanate mixtures in which the isocyanates or solutions obtained after phosgenation of the corresponding amines are subjected to a hydrogenation reduction treatment at a pressure of from 1 to 150bar and a temperature of from 100 to 180 ℃.

For example, patent document CN108864402A discloses a modified isocyanate excellent in storage stability and low in color number, and a method for producing the same. The antioxidant is selected from one or more of hindered phenol antioxidant, hindered amine antioxidant and phosphite antioxidant. By adding the antioxidant, the problem that the color number of unsaturated bonds of benzene rings in a diphenylmethane diisocyanate structure is higher due to thermal oxidation aging and free radical oxidation is mainly solved. In addition, the antioxidants selected are all of a very conventional structure in the art.

In summary, the present inventors have achieved the production of low color number diisocyanate products by innovative technical means, but none of the prior patents or technologies address the following needs: the diisocyanate product after freezing crystallization at-30 ℃ to 5 ℃ is melted again, the color number is obviously increased and the product is yellow-green. Therefore, it is highly desirable to develop a method for maintaining the physical properties of low color numbers of low-color-number diisocyanate products after freezing, crystallizing and resolubilizing.

Disclosure of Invention

The invention aims to provide a functional color reducing agent and a method for stabilizing the color number of a diisocyanate product aiming at the problem that the color number of the diisocyanate product is obviously increased after low-temperature freezing and remelting.

Diisocyanate is generally prepared by condensation of amine as a raw material to prepare polyamine and then phosgenation of the polyamine. Therefore, the prepared diisocyanate basically contains acyl chloride substances and urea impurities. For commercial diisocyanate products, the content of the acid chloride is generally in the range of 25-250ppm, and the content of the urea impurity is generally in the range of 400-1500 ppm. When the diisocyanate product undergoes low-temperature freezing crystallization, substances of the type gradually migrate to the packaging barrel core through pores of the crystals to be enriched, and as the concentration rises, the acyl chloride substances and the urea substances are combined with each other irreversibly to form salts, so that the diisocyanate crystals at the barrel core are yellow-green, the liquid diisocyanate product in the whole barrel after being dissolved is also yellow-green, and the color number is obviously increased. Thus, freezing crystallization and remelting make the color number of the diisocyanate product high.

The applicant finds that after a functional color reducing agent is added into the prepared diisocyanate product, irreversible combination of an acyl chloride substance and a urea substance in the low-temperature freezing and crystallization process of the diisocyanate product can be destroyed, and then a yellow-green salt substance is avoided, so that the color number of the diisocyanate product is stable, and the problem of the increase of the color number of the product is avoided.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

in one aspect, a functional color reducing agent is provided, which comprises the following components:

(a) a hindered amine-type substance, wherein the hindered amine-type substance,

(b) hindered phenolic and/or ester species;

wherein the mass ratio of component (a) to component (b) is 1:1 to 5:1 (e.g., 1.5:1, 2.5:1, 3.5:1, 4:1, 4.5:1), preferably 1:1 to 3:1, more preferably 2: 1.

The functional color reducing agent is a mixture, and can be a mixture of a hindered amine substance and a hindered phenol substance, or a mixture of a hindered amine substance and an ester substance, or a mixture of a hindered amine substance, a hindered phenol substance and an ester substance. In the research of the applicant, the hindered amine substance in the mixture is necessarily added, because the urea impurities contained in the diisocyanate product are combined with the acyl chloride substance in the freezing and crystallization process, and after the functional color reducing agent is added, the hindered amine substance in the diisocyanate product can be preferentially combined with the acyl chloride substance to destroy the irreversible combination of the urea substance and the acyl chloride substance. The hindered phenol substances or ester substances in the functional color reducing agent need to exert a synergistic effect with the hindered amine substances; the addition of the hindered phenol substance or ester substance can promote or accelerate the combination of the hindered amine substance and the acyl chloride substance, and the combination process is completely carried out. Therefore, the selection of the types of the component (a) and the component (b) and the amount ratio thereof in the functional color reducing agent of the present invention have an influence on the effect of color number stabilization.

The applicant also found in the research that the effect of stabilizing the color number of the diisocyanate is better when the content of the hindered amine substances is higher than the content of the hindered phenolic substances and/or ester substances in the functional color reducing agent. If the content of the hindered phenolic substances and/or ester substances is higher, the effect of stabilizing the color number of the diisocyanate is weakened; in addition, the addition amount of the hindered amine substance also needs to be controlled, and the effect of color reduction cannot be achieved easily when the amount is too small or too large.

According to the functional type color reducing agent provided by the invention, in some examples, the functional type color reducing agent is in a liquid state at normal temperature (at 25 ℃), and the viscosity of the functional type color reducing agent is 500-2000 mPas (at 25 ℃), preferably 1000-1500 mPas (at 25 ℃), and more preferably 1200 mPas (at 25 ℃). The viscosity of the functional color reducing agent is influenced by the ratio of the component (a) to the component (b).

According to the functional color reducing agent provided by the invention, in some examples, the molecular structure of the hindered amine substance is shown as the formula (I):

R₂—NH—R₁， (I)

in the formula, R₁And R₂The structural groups are the same or different and are respectively and independently selected from the structural groups shown in the formulas (i) to (v);

in a preferred embodiment, R₁And R₂The same, more preferably a structural group represented by the formula (iv).

For example, when R is₁And R₂The hindered amine is 4, 4' -bis- (2,3, 3-trimethyl-1-butenyl) diphenylamine; when R is₁And R₂The hindered amine substance is 4, 4' -bis (phenylisopropyl) diphenylamine; when R is₁And R₂And (b) the same, and is a structural group shown in formula (i), then the hindered amine substance is 4, 4' -di-tert-butyl diphenylamine.

In some preferred embodiments, the hindered amine species is selected from one or more of 4,4 '-bis- (2,3, 3-trimethyl-1-butenyl) diphenylamine, 4' -bis (phenylisopropyl) diphenylamine, 4 '-di-tert-butyldiphenylamine, and 4, 4' -di-sec-butyldiphenylamine, and more preferably from 4,4 '-bis- (2,3, 3-trimethyl-1-butenyl) diphenylamine and/or 4, 4' -bis (phenylisopropyl) diphenylamine.

According to the functional color reducing agent provided by the invention, in some examples, the molecular structure of the hindered phenol substance is shown as formula II:

R₄—HN—(CH₂)_n—NH—R₃， (II)

in the formula, R₃And R₄The structural groups are the same or different and are respectively and independently selected from the structural groups shown in the formulas (vi) to (vii); n is a positive integer, and the value of n is 1-8, preferably 4-8, and more preferably 6;

in the formulae (vi) to (vii), k is a natural number and has a value of 0 to 4, preferably 1 to 3, and more preferably 2.

In a preferred embodiment, R₃And R₄Also, the structural group represented by the formula (vi) is more preferable. For example, when R is₃And R₄The same as above and is a structural group represented by the formula (vi), the hindered phenol substance may be one or more selected from N, N ' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) diamine, N ' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) acetyl) diamine and N, N ' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) formyl) diamine.

In some preferred embodiments, the hindered phenolic is selected from the group consisting of N, N ' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) butanediamine, N ' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) pentanediamine, N ' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine, N ' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) heptanediamine, N ' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) octanediamine, N, one or more of N ' -bis- (2- (3, 5-di-tert-butyl-4-hydroxyphenyl) acetyl) hexamethylenediamine and N, N ' -bis- (4- (3, 5-di-tert-butyl-4-hydroxyphenyl) butyryl) hexamethylenediamine, and more preferably N, N ' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexamethylenediamine.

According to the functional color reducing agent provided by the invention, in some examples, the molecular structure of the ester substance is shown as the formula (III):

in the formula, R₅And R₆The structural groups are the same or different and are respectively and independently selected from the structural groups shown in the formulas (viii) to (ix); n is a positive integer, and the value of n is 1-8, preferably 4-8, and more preferably 8;

in the formulae (viii) to (ix), k is a natural number and has a value of 0 to 2, preferably 0 to 1, and more preferably 0.

In a preferred embodiment, R₅And R₆The same; more preferably a structural group represented by the formula (viii). For example, when R is₅And R₆And (viii), the ester is selected from one or more of bis (1,2,2,6, 6-pentamethyl-4-piperidyl) diacid ester, bis (1,2,2,6, 6-pentaethyl-4-piperidyl) diacid ester and bis (1,2,2,6, 6-pentapropyl-4-piperidyl) diacid ester.

In some preferred embodiments, the ester is selected from the group consisting of bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) adipate, bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) pimelate, bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) suberate, one or more of bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) azelate, bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) sebacate and bis (1,2,2,6, 6-pentaethyl-4-piperidinyl) sebacate, more preferably bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) sebacate.

In another aspect, a method for stabilizing the color number of a diisocyanate product is provided, wherein the diisocyanate product is mixed with the functional color reducing agent, and then is frozen, crystallized and re-melted to form a liquid, so as to obtain the APHA color number-stabilized diisocyanate product.

In the method, when the functional color reducing agent is mixed with the diisocyanate, the mixing time is the reference standard of ensuring uniform mixing. For example, the mixture may be stirred at 200 rpm for 30 minutes.

In some examples, the functional color-reducing agent is added in an amount of 0.001 wt% to 0.2 wt% (e.g., 0.002 wt%, 0.004 wt%, 0.005 wt%, 0.006 wt%, 0.008 wt%, 0.012 wt%, 0.015 wt%, 0.02 wt%, 0.04 wt%, 0.06 wt%, 0.1 wt%, 0.15 wt%), more preferably 0.01 wt% to 0.08 wt%, and still more preferably 0.02 wt% to 0.04 wt% based on the weight of the diisocyanate.

In addition, the addition amount of the functional color reducing agent needs to be controlled, and too small (less than 0.001%) or too large (more than 0.2%) is not favorable for the color reduction.

According to the method provided by the present invention, in some examples, the diisocyanate is selected from one or more of diphenylmethane diisocyanate (MDI), Toluene Diisocyanate (TDI), dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), 1, 5-Naphthalene Diisocyanate (NDI), Hexamethylene Diisocyanate (HDI), p-phenylene diisocyanate (PPDI) and 1, 4-cyclohexane diisocyanate (CHDI), preferably selected from diphenylmethane diisocyanate (MDI) and/or Toluene Diisocyanate (TDI), more preferably diphenylmethane diisocyanate (MDI).

According to the method provided by the invention, the Toluene Diisocyanate (TDI) can exist in various isomers. In some examples, the Toluene Diisocyanate (TDI) has a 2, 4-isomer content of 65 to 99.5 wt%, preferably 79 to 81 wt%, based on the total weight (e.g., 100 wt%) of the Toluene Diisocyanate (TDI).

The diphenylmethane diisocyanate (MDI) may exist in a variety of isomers. In some examples, the diphenylmethane diisocyanate (MDI) has a 4, 4-isomer content of 10 to 99.5 wt%, preferably 44.5 to 49 wt%, based on the total weight (e.g., 100 wt%) of the diphenylmethane diisocyanate (MDI).

According to the method provided by the invention, the temperature of the freezing crystallization is preferably-30 ℃ to 5 ℃ (for example, -28 ℃, -25 ℃, -20 ℃, -15 ℃, -12 ℃, -8 ℃, -5 ℃, -1 ℃, 0 ℃,2 ℃), and more preferably-18 ℃ to-10 ℃. Preferably, the temperature of the remelting is 60-80 ℃ (e.g., 65 ℃, 72 ℃, 74 ℃), more preferably 70-75 ℃.

According to the method provided by the invention, the difference of APHA color numbers of the diisocyanate before and after freezing crystallization and remelting treatment is preferably no more than 3# (for example, the difference is 2#, 0#), and preferably no more than 1 #.

The time of the freezing crystallization and remelting treatment is not limited herein.

The "APHA color number difference" as used herein means the absolute value of the difference between the APHA color number of the diisocyanate measured after the freezing crystallization and remelting treatments and the APHA color number of the diisocyanate product measured before the freezing crystallization and remelting treatments. The process conditions of the freezing crystallization and the remelting are as described above; the procedures and equipment for the freeze crystallization and the remelting are well known to those skilled in the art and will not be described further herein.

The functional color reducing agent comprises at least one hindered amine substance, and additionally comprises a hindered phenolic substance, an ester substance or a mixture of the hindered phenolic substance and the ester substance. The hindered amine substance can be preferentially combined with the acyl chloride substance to destroy the irreversible combination of the urea substance and the acyl chloride substance. The hindered phenol substance or ester substance can exert a synergistic effect with the hindered amine substance, promote or accelerate the combination of the hindered amine substance and the acyl chloride substance, and ensure that the combination process is carried out completely. According to the invention, the functional color reducing agent is mixed with the prepared diisocyanate finished product, and the frozen and crystallized diisocyanate product is re-melted at the temperature of-30-5 ℃, so that the problems of obvious color number increase and yellow green color appearance can be avoided, and finally the color number of the melted diisocyanate product is stable.

Compared with the prior art, the beneficial effect of this application technical scheme lies in:

after the functional color reducing agent is added, the irreversible combination of the acyl chloride substance and the urea substance in the low-temperature freezing and crystallizing process can be destroyed, and then the generation of yellow-green salt substances is avoided, so that the color stability of the liquid diisocyanate product obtained after the dissolution is ensured. After the diisocyanate is mixed with the functional color reducing agent, the obtained diisocyanate product can ensure that the APHA color number is basically unchanged or cannot be increased after being frozen, crystallized and re-dissolved at the temperature of between 30 ℃ below zero and 5 ℃, and has excellent color stability within a certain storage time.

Detailed Description

In order that the technical features and contents of the present invention can be understood in detail, preferred embodiments of the present invention will be described in more detail below. While the preferred embodiments of the present invention have been described in the examples, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.

< sources of raw materials >

For commercial diisocyanate products, the impurities present include acid chlorides, urea impurities, and the like. Wherein, the content of the acyl chloride substances is usually in the range of 25-250ppm, and the content of the urea impurities is usually in the range of 400-1500 ppm; the impurity content in the finished diisocyanate product is qualified as long as the national standard is met. The various types of diisocyanates have different color numbers due to various reasons, such as load adjustment of production facilities, process fluctuations, equipment performance fluctuations, photo-oxidation and thermal oxidation occurring during the reaction, and the like.

Toluene Diisocyanate (TDI) and diphenylmethane diisocyanate (MDI) from TDI and MDI units, respectively, of Wanhua chemical cigarette bench industry park;

4, 4' -bis- (2,3, 3-trimethyl-1-butenyl) diphenylamine, shanghai yi chen chemical company, ltd;

4, 4' -bis (phenylisopropyl) diphenylamine, shanghai yi chen chemical company, ltd;

bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) sebacate, shanghai-chen chemical company, ltd;

n, N' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexamethylenediamine, Shanghai Yichen chemical Co., Ltd.

< detection method >

APHA color number detection of diisocyanate product: a digital display colorimeter (manufacturer, BYK company, Germany) is adopted, and the detection standard is GB/T605-.